Conclusion All the "conclusions" of Pandas are false or irrelevant. Pandas "proves" that spontaneous generation is impossible, then claims that it occurred frequently throughout geological time (as instantaneous miraculous productions of new forms by designers). Biological organisms might exhibit some characteristics of manufactured things, but in basic ways they are fundamentally different. Changes are limited in experimental breeds because of the slowness of natural production of mutations. Increasing the mutation rate by radiation exposure makes further change possible. The fossil record does provide intermediate forms connecting the taxonomic groups. The patterns of similarity among organisms do not show what one would expect from common design by a single designer. And the molecular data, grossly misinterpreted by Pandas, do corroborate evolution and refute intelligent design! Furthermore molecular biology has shown that the hereditary material is full of extraneous copies, nonfunctional pseudogenes and other non-coding garbage, hardly the kind of "blueprint" that an intelligent designer would create. Throughout this critique, we have seen that "intelligent design" (creationism) is empty of explanatory power. The real phenomena do not even fit its alleged predictions.
I first became aware of the existence of the book "Of Pandas and People: The Central Question of Biological Origins" (1989. Percival Davis and Dean H. Kenyon, Haughton Publishing Company) when I attended a Bible Science Studies meeting held at the Scopes Ministries in northeast Oklahoma City on September 18, 1989. Don Patton, an associate of Carl Baugh at the Creation Evidences Museum at Glen Rose, Texas talked on two topics: The Coexistence Of Humans And Dinosaurs and How To Change The Textbooks. On the following October 23rd, the Oklahoma Board of Education textbook committee was going to hold a public hearing on the adoption of social science books for the public schools. A local creationist, Bill Nance, was trying to get support for changing some statements about the age of the earth in a world geography book that was up for adoption. Don Patton discussed the activities of the Texas creationists that were fighting the new textbook guidelines in that state. He produced a copy of this book and said it would be adopted as a supplement to the biology books in Texas. One of the advantages of this particular book was that it talked about "intelligent design" instead of scientific creationism. "Now we're not going to get scientific creationism in the textbooks; that has been ruled religious. We must avoid that term like the plague!" said Patton.
This book, which hereafter will be referred to simply as "Pandas" was not adopted as a supplement in Texas. It was also submitted for inclusion on the recommended list for science textbooks in Alabama where it was voted down. Several articles in NCSE Reports (Sept-Oct 1989, pp. 3-4; Nov-Dec, pp. 5-7; Jan-Feb. 1990, pp. 8-10) relate the details of the debate about Pandas before the Alabama textbook committee. Short reviews of the book have appeared by Eugenie Scott (NCSE Reports Jan-Feb 1990, p. 16), and by Gerald Skoog, Kevin Padian and Michael Ruse (Bookwatch Reviews 1989, vol. 2, number 11). Early in 1990, I got my copy of Pandas along with the Teacher's Guide from the publisher and decided to do an extensive in depth critique of it similar to my treatment of the six movie Origins series. I began this task towards the end of the summer and after about six months work finally finished it. Almost all the material here is new. Several of the supplements are taken from my previous document "An Evolutionist Goes to the Creationist Movies."
What's wrong with Pandas? A lot! The present critique is in the form of a running commentary on Pandas and as such necessarily contains some repetition. The sections on the Excursion chapters are heavily documented with references, both to technical papers and summary articles from such publications as Natural History magazine and Scientific American. I have probably gone overboard on this project—it contains more than 45,000 words and over 500 references and is probably longer than Pandas! But I hope that it will be of help to people who are interested in good quality science classes in our public schools.
Frank J. Sonleitner
Associate Professor of Zoology,
University of Oklahoma,
Norman, OK 73019
Co-liaison, OK Committee of Correspondence, February, 1991
Pandas claims a long intellectual history for evolution and creation (here called intelligent design). Many of the ancient myths only vaguely suggest evolutionary ideas and have little or no significance for the modern scientific theory of evolution. And many of them are mixtures of these two ideas. Even Genesis states that the universe was without form and its present organization was achieved in stages. White (1960) considers these ancient myths in detail.
Pandas' goal of presenting two alternative interpretations of the phenomena in six specific areas of science is laudable. Unfortunately Pandas' implementation has nothing to recommend it. Most of the facts are incorrect, many pertinent facts are omitted, many evolutionary concepts are distorted beyond recognition. For example, evolution is radically redefined. The mechanisms of evolution and punctuated equilibrium are grossly misrepresented. The nature of the fossil record is distorted and the existence of well-documented transitional forms denied. It is implied that pandas and marsupials cannot be fitted into a hierarchic classification. And finally, to discredit the protein sequencing evidence, Pandas claims that evolution requires a ladder of living forms, rather than a branching phylogenetic tree with the living forms at the tips. And after being fed all this misinformation, the students are asked to form their own opinion! If they believe what Pandas has presented, they will have been thoroughly deceived.
Pandas tells us that we observe natural and manmade objects, resulting from two fundamentally different causes: natural and intelligent. But are not manmade objects created by natural means? And what about other "manufactured" objects, such as beaver dams and the nests of birds, wasps and termites and the honeycombs of bees? Certainly letters of the alphabet scratched in the sand were manmade but what about the letters of the alphabet hidden in the colored patterns of the wings of various butterflies? The Mount Rushmore monument is obviously of human origin but what about the face of George Bernard Shaw so clearly shown by the outline and relief of Pointe Bernard Shaw on Isle Radisson in Quebec? What about the regular geological formations photographed on Mars that look like the ruins of cities or others that resemble faces? We must be very careful if we are to correctly recognize evidence of intelligent beings elsewhere in the universe. But we and scientists are dealing with intelligent beings that work by natural means, not the supernatural beings that Pandas will try to introduce into the science classroom.
Teachers do have the right to present nonevolutionary views in their classrooms. But these are expected to be legitimate scientific views and the teacher has the responsibility to present reliable information and describe scientific concepts and theories accurately and correctly. No creationist work, including the present one, meets those basic requirements.
Although Pandas restricts itself to six subjects, they are certainly not treated in depth. One peculiar feature of the book's organization is that the footnotes to the material in the Excursion chapters are not printed in this book but are found only in the Teacher's Guide. A listing of these references will be given and they will receive further attention in the critiques on the Excursion chapters.
As I hope this work shows, Pandas is not a balanced and intellectually honest treatment. It is (for a creationist work) a low-key and skillful polemic against evolution.
White, A. D. 1960. A History of the Warfare of Science with Theology in Christendom. In two volumes. A reprint of the 1st edition originally published in 1896. Dover Publications.
|Above: Letters of the alphabet in the wing patterns of butterflies (from Smithsonian 5(10): 28-29. January 1975). See also Amato, I. 1990. Insect Inscriptions. Science News 137(24): 376-377 (June 16). Above right: NASA Viking spacecraft photograph of "stone face" located in the Cydonia region, northern hemisphere, of Mars (from Discover 6(4): 92. April 1985).|
|Above: Aerial photograph of Pointe Bernard Shaw on Isle Radisson, mouth of Leaf River in Ungava Bay, Province of Qubec, Canada. The bottom of the picture is north (from Discover 6(6): 94. June 1985).|
Pandas' bibliographic entries contain a large proportion of incomplete citations and a number of misspelled names. The listings given below contain the necessary corrections. Pandas' footnote references appear only in the Teacher's Guide.
None for Overview sections.
Thaxton, C. B., W. L. Bradley and R. L. Olsen. 1984. The Mystery of Life's Origins: Reassessing Current Theories. N. Y. Philosophical Library Publishers.
Shapiro, R. 1986. Origins: A Skeptic's Guide to the Creation of Life on Earth. London: W. Heinemann Ltd.
Yockey, H. P. 1989. The Mathematical Foundations of Molecular Biology. N. Y. Cambridge University Press. (Note: I have not found this title in any of the library data bases available to me.—FJS)
Ambrose, E. J. 1982. The Nature and Origin of the Biological World. Chichester, West Sussex, England: Ellis Horwood Ltd.
Lovtrup, Soren. 1987. Darwinism: The Refutation of a Myth. N. Y. Methuen.
Augros, R. and G. Stanciu. 1987. The New Biology: Discovering the Wisdom in Nature. Boston. New Science Library of Shambhala Publications.
Denton, M. 1986. Evolution: A Theory in Crisis. Bethesda: Adler and Adler.
For centuries, the belief in spontaneous generation was considered to represent secondary creative acts of God. When the belief was finally laid to rest by the researches of Pasteur, all hopes of directly investigating the creation of living things by an intelligent being were dashed. But even as Pasteur was demonstrating that "full-blown" organisms did not arise de novo, he speculated on how life might have arisen gradually in stages from nonliving matter, foreshadowing the ideas of Oparin. According to today's view, the innate properties of matter and the deterministic laws of chemistry, under the proper conditions, would lead to the formation of living systems. Research in the field of prebiotic (chemical) evolution or biopoesis attempts to reconstruct the chemical steps and conditions leading to the origin of life.
Many experiments, attempting to simulate the conditions under which life arose, have been performed. Oparin's ideas and the experiment conducted by Miller were only the earliest attempts.
The researches of Fox have shown that polymerization of amino acids occurs readily by gentle heating and drying producing tiny cell-like proteinoid microspheres. Formation of RNA has also been accomplished in the laboratory. Although all these efforts have been given critical attention by scientists in the field and there are many unsolved problems, none of the criticisms mentioned by Pandas in the following sections have much validity.
Oxygen is a very reactive element. Free oxygen in the earth's atmosphere is a chemical anomaly explained by photosynthesis. Highly oxidized sediments, indicating an oxygen atmosphere, are almost a billion years younger than the oldest prokaryote fossils. Pandas' statements to the contrary are incorrect.
The direction in which a truly reversible reaction goes depends on the concentrations of reactants and products. If the products are removed by some other series of reactions, the first reaction will go in essentially one direction. Pandas' usage of the term "reversible" with respect to chemical reactions requiring large inputs of energy is incorrect. Many chemical processes used in industry require energy in some form, yet yield large amounts of product. Clearly, if Pandas' argument about energy making and destroying compounds is correct, we would never be able to make anything by adding energy! Of course there are traps in nature. For example, compounds synthesized by lightning would dissolve in rain drops and be washed down to the earth's surface where they would be safe from the next lightning flash, much as in Miller's apparatus.
The restriction of biochemicals to specific three-dimensional forms would have arisen after the evolution of enzymes to catalyze reactions. Prior to the advent of biological enzymes, reactions might have been catalyzed by clay minerals which adsorb the reactants on their surfaces.
In actual experiments, the predominant outcome may be large yields of "goo" which has never been fully analysed so we don't know if it is non-biological or not. There is now some evidence that it is proteinaceous. And this material is found in meteorites and there is spectrographic evidence for it in the atmospheres of the outer planets and some of their moons. So some sort of chemical reactions, similar to those occurring in laboratory experiments, must have occurred in nature. Obviously not all the amino acids, etc. formed in these experiments are incorporated into this material. There are always a good deal left over in solution which can be analysed and identified.
Pandas says that all things result from two kinds of causes; natural and intelligent. Their classification implies that intelligence is unnatural! How do other "manufactured" items, such as beaver dams, and the nests of birds, wasps and termites fit into such a scheme? The analogy of the coded information in DNA to a message in a known language is highly exaggerated. The information is not organized into "words, phrases, and sentences." Even if scientists succeeded in determining the entire base sequence of an organism's genome, they would still be far from understanding how an organism results from that information. Because that information codes for many polymers of RNA and protein and the sequence in which they are to be synthesized so that their inherent self-organizing properties will "make" the organism. Also, molecular biologists have discovered that a large proportion of that "information" is nonfunctional nonsense.
When we find "John loves Mary" written in the sand, we assume that somebody scratched those letters there with a stick or with their fingers, because we have seen other people write similar messages in sand or mud. We probably have done it ourselves. People are part of nature, their bodies "obey" all the natural laws; they are a natural cause.
Observation clearly shows that DNA and protein (and new organisms) arise by various reproductive processes; changes in these materials and organisms have also been observed to arise by natural causes. In this regard, the theory of evolution follows the Principle of Uniformity. The same processes that we can observe producing organisms today and that we even use to modify organisms are those that acted in the past to produce the present day biological world. To say that this logically entails assuming that the "John loves Mary" message arose from the action of the waves is nonsense! All our observations on the reproduction of DNA and organisms indicate that Pandas' assertion that all information must be produced by "intelligence" is arbitrary and unwarranted. The idea that DNA originated from an "intelligent cause" is based on experience is nonsense. We have never seen an "intelligent agent" make DNA (other than biochemists in a laboratory). What would the agent look like? What would the phenomenon look like?
The idea of an "intelligent" agent producing life is not based on experience, but on a very weak analogy between organisms and manufactured objects that has been rejected by all modern philosophers beginning with Hume (author of the uniformity principle) in the 18th century. In fact this idea rejects the principle of uniformity, claiming that the "intelligent agent" only acted in the past and is not acting at the present time. At the present time, organisms come into existence by the entirely different phenomena of reproduction. Most "design proponents" (creationists) claim that the "intelligent agent" is a supernatural being, namely the Christian God, and that science is incapable of comprehending this creator and the creative process.
The hypothesis of biopoesis (the natural origin of life from nonliving matter) can be tested and serves as a guide for much fruitful research in biogeochemistry. Pandas (like all other creationists before them) makes no attempt to understand or investigate the nature of the "intelligent agent" but assumes that it is supernatural and beyond the realm of science. This is stated explicitly by Thaxton in the section at the end of the book entitled "A Word to the Teacher."
The short historical background that introduces this chapter is full of errors. Pandas' comments about Lamarck's views are incorrect. Body structures, etc. do respond to the organism's needs or habits. But these changes are not passed on to the organism's offspring, i.e. they are not heritable. As for Darwin, it was common knowledge that variation exists and occurs in species; animal breeders made use of it in producing new breeds. Mendel's laws of heredity do not explain how new traits are produced; only how existing traits are transmitted to offspring.
Pandas suggests that Mendel's work was antithetical to Darwin's and hence was "not taken seriously" until the twentieth century. Mendel was an ardent follower of Darwin's and considered his discoveries as the solution to the apparent problem of blending inheritance swamping out variations before they could be selected for. Few biologists were aware of his work, it being published in an obscure journal. Those who did read it were put off by its mathematical nature. Around 1900, his principles and his journal article were independently rediscovered by several geneticists. Pandas contradicts itself, now saying that Mendel's work was welcomed enthusiastically and integrated into evolutionary theory forming Neo-Darwinism.
In the final paragraph here, Pandas again seems unaware that neither blending inheritance nor Mendelian genetics address the question of the origin of new variants. On the other hand, blending inheritance would actively wipe out new variations, while Mendelian genetics results in a neutral stability preserving new variants (mutations), giving natural selection the opportunity to work with them. The stability that Mendel discovered is just what is needed for evolution to be possible!
Pandas seems to think so. Of course natural selection can't foresee what is needed; it does not produce the new hereditary raw materials that it selects. Natural selection is differential survival and reproduction that tends to weed out the less fit and conserve the more fit. In doing so it definitely guides and determines the direction of evolution.
This section does not live up to its title, but introduces typical creationist concepts of horizontal versus vertical change and radically redefines evolution. To Darwin, evolution was descent with modification; to population geneticists, it is a change in gene frequencies. But here it is redefined as "the transformation of one type of organism into another." This definition of evolution is found in the creationist biology text, Biology, A Search for Order in Complexity, edited by J. N. Moore and H. S. Slusher, pp. 420, 431. But Pandas (as well as other creationists) refuse to give an operational definition of "type" or "kind". How can they say that breeders have never turned one kind of organism into another if they can't give us an operational criterion for distinguishing "kinds"? How can they tell if macroevolution has occurred or not?
Gene recombination is a tremendous source of variation. Pandas says that "if bred too far" (whatever that means) the animals become infertile and die out illustrating that there is a limit to how much animals can be changed. Research has shown that gene alleles for sterility may be closely linked on the chromosomes to the genes being actively selected and this brings about the sterility. If selection is relaxed for a few generations, crossing-over will decouple such alleles and selection can then continue without resulting in sterility. Eventually, however, one will exhaust the existing reservoir of variation and must wait upon mutations before further progress can be made.
Most mutations result from copy errors during reproduction of the genetic material. Although Pandas says that mutations do not create new structures, but merely alter existing ones, that's the stuff that makes evolution! For the most part, vertebrates (and other groups of organisms) are distinguished from one another by the changes in structures that they all possess. Pandas claims that for all the altered structures produced by mutations in "The fruit fly" they have not created a new kind of wing or a new kind of insect. Again, what would constitute a new kind of wing or insect? Pandas claims that virtually all mutations are harmful. Actually most mutations are neutral, many of those producing small changes are beneficial, only most of those producing large, easily detected changes are harmful. In a way, mutations are akin to typing errors, but the analogy easily can be pressed too far.
It is Pandas' opinion that all the changes observed in the lab or breeding pen represent microevolution. Previously Pandas stated (p. 9) that breeders have produced differences greater than those between natural species. Many evolutionists would consider those macroevolutionary changes. Virtually all evolutionists today believe that macroevolution is compatible with microevolutionary processes. None of the new suggestions (such as punctuated equilibrium) require a new genetic theory to explain macroevolution.
Giraffes are browsers feeding on leaves of trees and shrubs. They normally do not graze on grass. Interestingly enough the photograph of a giraffe drinking (p. 12) clearly shows that a giraffe's neck is not long enough to reach the ground. The giraffe must assume a very awkward posture of spreading and/or bending its front legs in order to reach the ground! In certain parts of Africa where the foliage is sufficiently succulent, giraffes rarely, if ever, drink water.
Contrary to Pandas' statements, there is nothing very special about the giraffe's circulatory system. It does have a much higher blood pressure than most other animals, but all other the other hoofed mammals with "normal-sized" necks have the same system of blood pressure controls. There is no danger of the blood vessels in the lowered head of the giraffe bursting any more than at the bottom of its long legs, the increased pressure in the extracellular fluids of the giraffe's tissues exactly counteracts the increased blood pressure. All of the features of this "adaptational package" are found in other mammals, including the short-necked relative of the giraffe, the okapi. Thus the problem posed by Pandas, of all the adaptations occurring simultaneously, is a pseudoproblem. All the elements of the overall integrated package are shared by present day mammals and undoubtedly were present in the giraffe ancestor.
Pandas' calculation of how likely it is that random mutations will come together and coordinate to form a new structure is based on the assumption that all of the necessary mutations occur simultaneously in the same individual. The evolutionary mechanism has four main components: mutation, reproduction, genetic recombination and natural selection. Pandas is ignoring the last three components. Also evolution most often proceeds, not by producing truly new structures, but by modifying old ones. Mutations producing beneficial modifications may occur in various individuals, where reproduction and natural selection will cause them to spread through the population in the course of succeeding generations and genetic recombination will eventually bring them together in many individuals. Computer simulations have shown that if such mutations occur, their eventual combination together is virtually a certainty. Pandas' calculation is totally irrelevant because it is based on wrong assumptions about the nature of the evolutionary mechanism.
Again Pandas' analogy about the plumber and electrician is irrelevant. The giraffe does not have a "new" body plan. Its body plan is a typically mammalian one, only certain parts have been modified as to their size and shape.
One could build a palace by tinkering with a tool shed and adding bits and pieces here and there. It probably wouldn't look like the usual palace but it might serve the functional purpose just as well. And the biological evidence shows conclusively that the "higher" vertebrates evolved through modification and tinkering with a developmental system that originally produced fishes. For example, many of the structures in the head and neck of terrestrial vertebrates are modified from a set of gill pouches, arches and bars that are produced in the early embryo. In truth, the palace did originate in bits of marble added to the tool shed! The intelligent design view, what there is of it, does not fit the facts. Pandas "evidence" against evolution is couched in terms of a creationist definition of evolution and the undefined terms "kind" and "type".
Again Pandas claims that there are limits to variation within existing groups of plants and animals but still refuses to suggest what those limits are and what "groups" are. Are the existing groups which define the boundaries of variation species? genera? families? The variation in dogs is equivalent to that found in some "natural" genera. The variation in the Hawaiian honey creepers is equivalent to that distinguishing other families of birds.
Species are characterized by their reproductive isolation from other species. The degree of visible difference between closely related species may be quite considerable or it may be virtually nonexistent. There are many different mechanisms of reproductive isolation besides the geographic and ecological mechanisms mentioned here. Also, all degrees of reproductive isolation are found in nature; it is not an all-or-none phenomenon.
Reproductive isolation, initiated by geographic barriers is called allopatric speciation and is considered to be the almost universal mechanism that produces new species. Many well-known cases of "breeding chains" are known in various groups of birds, amphibians and butterflies.
Pandas is very naive in speaking of the North American fruit fly, as if there were only one! The hawthorn and apple fruit flies mentioned in this section belong to the family Tephritidae which includes 290 North American species! Tephritid larvae infest and feed on fresh fruits and hence may become economic pests in contrast to the Drosophilidae (190 North American species) which attack decaying fruit. Tephritid flies are about the size of house flies whereas drosophilids are much smaller. The importance and commonness of reproductive isolation resulting from ecological isolation is controversial, although the phenomenon has been produced in the laboratory using Drosophila in population cages.
These mechanisms produce changes in genetic information, not necessarily losses in genetic information. No genes are lost. There are changes in the proportions of the alleles of various genes and some of the alleles might be lost, but this variation is replenished by subsequent mutations.
There is no question that speciation is evolution. This is a fictitious problem created by Pandas. But what is evolution? Again, to Darwin, evolution was "descent with modification"; to population geneticists, it is "a change in gene frequencies." Pandas insists on a new definition. Change is no longer enough. "New" genetic information must be introduced producing "new" levels of complexity. Pandas doesn't tell us whether mutations that produce new versions of a gene are sufficient or whether the production of new, additional genes (which usually occurs by mutation of duplicate copies of an existing gene) is necessary to meet their new criterion.
Pandas claims that speciation is microevolution. Many biologist, especially those favoring punctuated equilibrium, consider it macroevolution. According to Pandas, microevolution doesn't add new levels of complexity. By Pandas' definition, it isn't even evolution! It only produces "horizontal diversification." The evolution of the many orders of mammals or of insects was brought about mainly by changes in structures, rather than the production of truly "new" structures. Are these great adaptive radiations of forms only "microevolution"? If a geneticist transformed a fruit fly into a beetle, would this be evolution? Are beetles more complex than flies? To a lesser extent, the evolution of mammals from reptiles involved similar changes in old structures. The wings of birds are modified front limbs and feathers are modified scales. Are all these evolutionary changes to be considered microevolution—a kind of nonevolutionary diversification? If this is so, is Pandas willing to admit that such extensive changes in biological form are possible by natural means?
Yes, speciation is very much like what breeders do. Centuries of breeding have produced a great deal of change. The various breeds of dogs exhibit variation that in nature would be sufficient not only to define new species but even genera. This is quite remarkable, considering the very small populations that breeders work with, which precludes the likelihood of many mutations augmenting the genetic variation available for selection. The variation in the Hawaiian honeycreepers mentioned at the beginning of this overview section display variation equivalent to genera, families and even possibly orders among other birds.
Only a small fraction of the known phyla have any fossil record, thus Pandas' statement that virtually all of them appear at about the same time in the fossil record (at the beginning of the Cambrian period) is not based on evidence. Even those few that are represented in the fossil record, appear at different times, before, during and after the Cambrian.
There are transition series of fossils leading from fish to amphibians, amphibians to reptiles and from reptiles to birds and mammals, in some instances making it difficult to discern the boundaries of the classes. This is especially true of the amphibian-reptile and reptile-mammal transitions. Archaeopteryx has all the skeletal features of a theropod dinosaur and is often classified with them in the modern literature. Yet it had feathers and primitive wings revealing its relationship to the birds.
Fish do not have all the characteristics of true fish from the earliest known fossils. The earliest fossils lack jaws, paired limbs and bony internal skeletons. The earliest amphibians had many of the characteristics of fishes. Usually fossils only provide knowledge of skeletal anatomy, so we don't know if the earliest reptiles had all the characteristics of "true" reptiles, but their skeletons are hardly distinguishable from those of the amphibians of their day. And there is a large series of reptiles, the synapsids, who over time gradually acquired more and more mammalian characteristics, eventually resulting in "true" mammals.
Pandas seems to have gotten this argument backwards. All the palaeontologists who emphasize stasis apply it to the species! In the course of geological time, the species composition of the higher taxa change, so those taxa definitely do not exhibit stasis.
It is unreasonable to expect to find long continuous chains of transition forms in the fossil record. Consider the evolution of the modern horse from eohippus, which occurred over a period of 60 million years. If we assume a generation time of three years, that corresponds to 20 million generations. Let us further assume that it takes 1 foot of sediment to bury a horse (probably not enough for the larger, more recent horses, but more than enough for the dog-sized early ancestors, so 1 foot is a reasonable average). To get a really complete series of transitional forms, we would require at least 1 specimen from each generation. But, if every three years, a river flood buries one horse or horse ancestor under 1 foot of sediment, that eventually amounts to 20 million feet of sediment! Which translates into 3,788 miles, a figure almost equal to the radius of the earth! The total thickness of the Tertiary sediments in western North America that contain the fossil equid sequence is a bit under 10,000 feet. Thus only a tiny fraction of a complete transitional series could have been preserved. Yet, the known fossil horses provide a fairly continuous record with only one or two small gaps.
Obviously the transition series that we have in the fossil record are not 100% complete. Many gaps still remain. But remember, whenever another transition form is found, it divides a gap into two smaller ones! As long as the fossil record remains incomplete the number of gaps will not decrease! The fossil record is like a motion picture sequence which is made up of a series of still frames, each one representing a small change in the picture and the whole series of them representing a transition sequence between the scene at the start and at the end of the series. Yet there is a short time "gap" between the frames. The frames represent fossil species, forming the transition sequences which are known in the fossil record. Transitions between species (the gaps between motion picture frames) are much rarer, but examples of those also are known.
Archaeopteryx is an intermediate form between reptiles and birds that fulfills the evolutionary prediction of transition forms between those two classes. Why should intelligent designers produce such a form? (Here it is considered an "odd-ball" type, but in Excursion chapter 4, it is considered a "true" bird.) The leathery bill of the platypus is only superficially like the bill of a duck. Its skeleton and organ systems are a mixture of mammalian and reptilian features. Some biologists consider that it is more closely related to the mammal-like reptiles than the true mammals.
Fossils do form graded series! Living species of horses form a cluster separated from the living species of tapirs. But when one considers the fossil forms, there are known graded series leading back from each set of living forms and converging on a common ancestor in the Eocene period.
The main principle of Darwin's theory is evolution guided by natural selection. No evolutionists reject this. Punctuated equilibrium is only a minor modification of Darwinian evolution. It assumes that species (not taxa in general) remain relatively stable and that most evolutionary changes occur during speciation, which takes anywhere from 5,000 to 100,000 years (not hundreds of years). The changes that occur at speciation come about by conventional microevolutionary mechanisms. Because the transitional forms are restricted in time and space, they are unlikely to be found in the fossil record.
Punctuated equilibrium is not based entirely on negative evidence. Fossil examples of transitions between species are known and these are restricted in space and time relative to the occurrence of the species themselves just as the hypothesis predicts.
If design theory requires that various forms began abruptly with their various features intact, then it is wrong. The first fishes lacked jaws, paired limbs and bony internal skeletons. Birds first appeared with feathers and primitive wings but not with any of the skeletal specializations of modern birds. Did mammals first appear with fur and mammary glands? Those features don't fossilize. Indirect evidence would indicate that some mammal-like reptiles had them but again these forms did not possess all the mammalian specializations of the skeleton and reproductive systems. Of course, creationists could backpedal on these predictions and say that the designer(s) experimented with many versions before they got the designs just right.
We are given the evolutionary interpretation of the fossil record and if we pay homage to the principle of uniformity the organisms of more recent times must be the descendants of those of earlier times. Remember Pasteur proved that life only comes from life.
But just what is the "intelligent cause" interpretation? Very little is said about it because it could prove to be very embarrassing. Some creationists believe that the world is very old and others believe that it is no older than a few thousand years and that all (or some combination) of the geological strata are the result of a worldwide flood. There is hardly any common ground between those two views.
But let's take the fossil record at face value. If fossils are lacking, it's because such forms never existed. Fossil species come and go. The designers kept making more and more new designs with the passage of geologic time. And they apparently kept on eliminating old designs just as fast. At the beginning of the Paleozoic era they must have been trying out new designs for phyla at a furious pace. And apparently they changed their minds many times. Most taxa do not have continuous fossil records. We must conclude that the designers wiped them all out and then at a later time reinvented them. The coelacanths are a nice example. The designers wiped them out in the Cretaceous and then, for what reason, recreated them in the form of the present day genus Latimeria.
The fossil record does establish evolution as a fact, because as Pandas has shown, the intelligent design proponents (creationists) cannot come up with a reasonable alternative. Naturally, all organisms that lived long enough and survived to form fossils would be fully-formed! Any partially-formed ones would not be viable. But an animal can be fully-formed and yet not have all the features characteristic of its group. The platypus and Archaeopteryx are excellent examples of this.
Evolution is a scientific theory; it offers detailed testable mechanisms. Intelligent design is not because it does not offer detailed testable mechanisms. The designer(s) are vague shadowy concepts providing no real understanding of the phenomena of the living world.
As Pandas says, living things do fall into a neat group-within-group arrangement. Yet Pandas directly contradicts this statement later in the chapter, by using vague terms such as "patchwork pattern", "contradictory similarities" and "living mosaic"! The common body plan of vertebrates involves the anatomical features of all their organ systems, not just the skeletal system as the overly simplified Figure 6 implies. The pattern of similarity is augmented by the data from the fossil record, from which palaeontologists have been able to trace lines of descent connecting the present day living groups.
Birds and fish have very much more in common than feathers and scales respectively. The only problems with classifying vertebrates into the various classes occurs with the transition fossils (mentioned in the previous section) that bridge the gaps between those classes.
Certain marsupials and placentals are superficially similar. The only thing flying squirrels and flying phalangers have in common is that they are small mammals with long tails and flaps of skin forming gliding membranes. In skeletal structure the North American wolf and now-extinct Tasmanian wolf are clearly distinctive. If found as fossils, they would never be counted as members of the same species! Palaeontologists have no trouble distinguishing marsupial and placental fossils from one another. The two "wolves" differ in many ways in addition to their different modes of reproduction. The same holds true for the other marsupial-placental "look-alikes", they are similar in some of their ecological adaptations, but the marsupials all share basic skeletal, dental, reproductive, neurological, behavioral, developmental and other features. Even the 19th century pre-evolutionary anatomists recognized the distinction between marsupials and placentals.
Although Linnaeus based his classification on structure, the terms homology and analogy were not invented by him, but by the 19th century British anatomist, Richard Owen. Homologous bones for example, are the corresponding parts in various animals, with the same relationships to the adjacent bones, corresponding muscles, blood vessels, nerves, and with a corresponding similar developmental origin, etc. This is how homologous structures were identified by both the pre-evolutionary and the evolutionary biologists. The more details that are identical in a specific structure in a variety of forms, the more likely it represents a homology—part of the basic archetype (in the philosophy of pre-evolutionary anatomy) or derived from a common ancestor (in evolutionary theory). Analogous structures always exhibit differences in the details of their structure; their similarities are usually the result of functional constraints. There is one best streamlined shape for a fast swimming aquatic organism, all limbs for digging will have shovel-like shape; all wings must meet certain rigid aerodynamic requirements, etc. Difficulties in sorting out homologies and analogies occur in closely related organisms in structures which are a mixture of homology and analogy.
Pandas, which has greatly exaggerated the similarities of the placental and marsupial "wolves" should give illustrations of those "structures of astonishing similarity at first regarded as homologous . . . later determined to be analogous."
The present day view is that the giant Panda is a bear and the red panda a racoon, but it must be remembered that bears and racoons themselves are closely related. That, along with the fact that the two pandas are adapted to similar habitats, made the analogies and homologies hard to sort out. But the newest biochemical data have settled the question. Also, detailed comparison of the chromosome structures of the two pandas indicates that the giant panda is related to the bears and the red panda to the racoons. Pandas is wrong in this regard. Pandas is also wrong in gracing the red panda with a "panda's thumb." Furthermore, Pandas' view that living things are like collections of pre-assembled units would predict that the intelligent designer would have endowed pandas with a true opposable first finger and not with this rather crude "fake" thumb unique to the Giant Panda. This is more like a case of natural selection making do with materials at hand (like a tinkerer) to assist the panda to strip leaves from the bamboo.
It is one of the central problems of taxonomy to distinguish between analogies and homologies. This was just as true for the pre-evolutionary 18th and early 19th century taxonomists as it is for the evolutionary taxonomists. As we have already mentioned the criterion for homology is the degree of detail to which similar structures correspond in different organisms, not only in their own structure but in their relations to associated parts and in their development. This same criterion was used by the 19th century pre-evolutionary biologists as well as their evolutionary successors. Obviously this criterion is independent of evolution. Thus citing homologous structures as evidence of evolution is not circular reasoning.
Prior to the great voyages of exploration beginning in the 15th century and the invention of the microscope in the 17th, scholars had very limited knowledge of the diversity of living things. Biological classification was only a casual activity until the eighteenth century when it was taken up in earnest as a biological discipline. The concept of types and archetypes was an arbitrary philosophical scheme, quite different from the biblical idea of special creation. True, many things can be classified that are not derived from a common ancestor, but then they are not always arrayed into hierarchical classifications. What makes "all Fords look similar" is not the "pattern in the mind of the person making them" but the collective input of the activity of a team of engineers that may number as many as 12,000. Making human designers as the basic analogy would not suggest a single "primeval"(?) intellect but many teams, each consisting of a large number of designers. As for piggybacking on existing patterns, the earliest automobiles did resemble the horse-drawn carriages of their day, but the parts of modern automobiles are totally different, with no traces of the horse-drawn carriage in them; and NASA's Apollo spacecraft and the Space shuttle were, in fact, designed from scratch! In contrast, mammals (including humans), retain many marks of their fish ancestry.
The "puzzle of the marsupials" is again misrepresented. It was not patterns for wolves, cats, squirrels, etc. that evolved twice, but more general patterns for cursorial predators, stalking predators, herbivores, burrowers, etc. that evolved. There are only superficial resemblances between the ecological homologues among the marsupials and placentals. This was accomplished not by mutation along but by mutation guided by natural selection producing similar (but not identical) features adapted to similar ecological ways of life.
Flight did evolve four times. The flight adaptations in the four groups mentioned differ in many important respects, especially when one compares the insects and the vertebrates. If one intelligent designer is responsible for them all, why aren't the flight adaptations identical? And why should there be four different flying groups to begin with? Four types of airplane, exhibiting design features as different as those in the four groups of flying organisms would only have been produced by four different, independent designers (or rather, teams of design engineers). Clinging to the designer analogy, is Pandas suggesting that different teams of intelligent designers are responsible for these flying organisms?
Taken all together, all the similarities and differences do trace a branching pattern indicating evolutionary descent. It is important to note that the basic classification used today was established by pre-evolutionary biologists. Any superficially ecological adaptations are clearly derived from the more basic structures shared by members of the different groups and do not represent a pattern of fixed patterns of discrete blocks. If this were so, we would expect all flying organisms to have identically constructed wings, or identical sets of carnassial teeth, etc. Hemoglobin would appear to be such a fixed pattern or discrete block but it clearly evolved independently from myoglobins which are universally found in eukaryote organisms.
In the following section, the protein cytochrome c, a perfect biological example of a pre-assembled unit "that can be plugged into a complex electronics circuit", is considered. The intelligent design hypothesis predicts that it should be identical in all forms yet it exhibits a pattern of structural variation that definitely supports evolution.
Certainly the biochemical data on the amino acid sequences of related proteins provides a great many more homologies upon which to base classification. And the biochemical classifications confirm those produced by traditional methods, indicating that the earlier taxonomists did a good job of sorting out homologies from analogies. Pandas doesn't mention it, but the biochemical classification supports the distinction between the marsupials and the placental mammals. Pandas tried to express some vague dissatisfaction with that classification in the previous section.
The new findings of biochemistry are important new evidence for evolution and against creation (or intelligent design)! As we shall see with the example of cytochrome c, the intelligent design hypothesis cannot explain the results.
This is in total contrast to what Pandas says. But cytochrome c does not illustrate Pandas' principle that similarity in structure reflects similarity in function! And why did the intelligent designers create an ecological web and food chains? There is no corresponding phenomena among human manufactured products! Predators and prey are somewhat analogous to weapons and counter-weapons, which are usually conceived and designed by different and antagonistic teams of designers. Are we to assume the same is true for the designers of organisms? But since Pandas asserts that intelligent designers did this, and made all organisms out of the same basic substances so that the food chain would work, why did they make plants out of cellulose and lignins and then forget to endow the herbivores with enzymes to digest those materials?
Pandas demonstrates that the data in Table 1, taken column-wise corroborates traditional taxonomic categories. The hierarchic classification of organisms supports the evolutionary idea that those categories inherited their common features from common ancestors.
But the data, taken row-wise is supposed to refute evolution! This argument is based on Pandas' illogical and irrational assumptions. They arrange the animals listed in the table into an evolutionary ladder, which implies, among other things, that the present day humans evolved from the present day Rhesus monkey; that the horse evolved from the rabbit; that the dogfish evolves from the silkworm moth which in turn evolved from wheat! Nothing could be more wrong and idiotic! Evolution doesn't produce a single linear series, especially of present day living forms, but a branching phylogenetic tree, of which the living forms represent the tips of the branches. All the eukaryote organisms differ from the bacterium by the same percentage because they are all equidistant in time from their common ancestor with the bacterium.
Similarly certain fish evolved into amphibians, but the organisms involved were Devonian crossopterygian fishes that produced amphibians like Ichthyostega. If the cytochrome c proteins of those long extinct forms were available, we would expect them to be very similar. But not the cytochrome c proteins of the present day carp and bullfrog! None of the present day living forms represent intermediate forms between the various vertebrate classes. The similarities in cytochrome c of the various taxonomic groups are explained by evolution as due to the recentness in time of their common ancestors.
But why are the cytochrome c proteins different? Cytochrome c performs exactly the same function under the same physiological conditions (inside the mitochondria) of all the organisms considered (except the bacterium, which don't have mitochondria). Over geologic time, random neutral mutations have produced amino acid substitutions in cytochrome c which did not change or affect its functioning in any way. Some of these mutations became fixed in their populations and were passed on to the species that evolved from them. The molecular clock does not assume a uniform rate of mutation, only a long-term average rate of fixation of neutral mutations. Thus Pandas' argument about mutation rates being related to reproduction rates is irrelevant. That argument is also erroneous; mutation rates may be related to generation time. The fact that different proteins seems to have molecular clocks running at different rates is to be expected. Some proteins have more rigorous functional constraints on their amino acid constituents than others, thus there will be fewer possible neutral mutations in those proteins.
If the differences in cytochrome c are due to accumulation of random, neutral mutations, then the similarities in cytochrome c structure that say, all vertebrates share with insects, plants and bacteria, can only be explained by common ancestry! That makes these data direct evidence for evolution and not just another criterion for classifying organisms.
It has been conclusively proven that cytochrome c is an enzyme performing an identical function in all the organisms considered and is a perfect example of a "pre-assembled" unit that Pandas refers to at the end of the preceding section. Thus if all these forms were created by an intelligent, rational designer, cytochrome c should have an identical structure in all these forms. But it doesn't! So why is this enzyme different in the various classes?
Even if creationists fall back upon a molecular clock model (the clock running about a million times faster than the evolutionists postulate), the expected results would be different. Because all these forms would be equidistant in time from their creation, they all should be equally different from one another (say 65% different). Thus the creationist is almost forced to assume that these differences in cytochrome c structure are somehow adaptive (i.e. functionally significant) in the various forms. But all the biochemical evidence points to the fact that the observed differences in amino acid sequence are neutral and have no effect on the function of cytochrome c. That in fact is what makes the molecular clock plausible. Thus the creationists must present some specific explanations as to the function of these structural differences in cytochrome c. Even if they succeed in doing so, they still have to explain why the sequencing data from other proteins (and DNA and RNA) all produce the same hierarchical groupings. The results of DNA, RNA and protein sequencing provide some of the most significant evidence against creation (or intelligent design) and for evolution.
In a superficial way contemporary organisms might appear to fit a theory of intelligent design (although Pandas does not offer one with any detail, only some vague undefined generality.) But the fossil record does reveal the transitional forms and connecting links between the various taxa. Pandas' denial of this fact, based on a tremendous amount of evidence, is simply false. Palaeontologists are not abandoning Darwinism for some new theory of sudden change. This is a gross misinterpretation of punctuated equilibrium. Although many fossil species are separated by gaps, the sequences of the species themselves represent transitional stages. No palaeontologists deny this.
The biochemical data clearly can only be explained by evolution. Pandas' argument against this is based on the false premise that living organisms must be lined up in a true evolutionary series or ladder.
All the data from a variety of fields come together like pieces in a jigsaw puzzle that supports evolution. No creationist has ever been able to make such a synthesis to support creationism. Certainly Pandas does not do it.
(from Frank Sonleitner's critique of Of Pandas and People)
Outline of the Pandas Chapter
Scientists today propose two general explanations:
Origin by an intelligent designer (creator) is tenaciously held by certain religious groups who, for political reasons, pretend that it is a scientific explanation. Everything about the creation is claimed to be supernatural (Morris, 1974, pp. 11-12) which means the creator and its activities is beyond human understanding (Bassinger and Bassinger, 1978). Hence this idea is not an explanation (let alone a scientific one) but a reaffirmation of a religious miracle. Any scientists that espouse this idea do it for religious reasons (i.e. the Bible says so) and not because of any scientific evidence for it. They have admitted this in court proceedings (Lewin, 1982a ). In fact, creationists have stated that it is impossible to know anything scientific about the origin of life (Morris, 1963, p. 56; Morris, 1967, p. 19, 59-60; Morris, 1972, p. 16; Morris, 1974, p. 4; Gish, 1973, p. 8).
Spontaneous generation as "a process of self-organization without outside intelligence" (Pandas, p. 41, 43) is a modern-day creationist-concocted definition. For many centuries, spontaneous generation was the more-or-less instantaneous appearance of complex organisms. For many Christians, it was the visible, present-day creation of organisms by God (the creator, intelligent designer, etc.).
Spontaneous generation is a belief that has persisted throughout history. People believed that spontaneous generation came about as the result of secondary supernatural creative acts of God. This belief was incorporated into Christian theology and, beginning in the 4th century A.D., appears in the writings of all the great Christian theologians, including Basil, Gregory, Augustine, Bede, Isidore, Lombard and Aquinas (White, 1960, vol. 1, pp. 42, 46, 52-56; Oparin, 1953, chapter 1). Thus it is really the creationists who, for centuries, believed in spontaneous generation.
Although Pasteur proved that spontaneous generation of present-day organisms from inorganic matter did not occur, "he nevertheless believed in the possibility of abiogenesis and attempted to produce life artificially in the laboratory." This belief "stemmed from his conception of an 'asymmetric force,' the intervention of which he considered essential to the production of asymmetric molecules and, hence, of life." Pasteur's main opponent in the spontaneous generation controversy, Pouchet, was a creationist who believed that spontaneous generation was part of God's grand design, and a vitalist—only organic chemicals, that still retained some "force plastique" could give rise to organisms (Farley, 1977, pp. 108-119 for Pasteur's various views on the matter; pp. 114-115, 117-118 in particular for asymmetric forces; pp. 98, 116 for Pouchet).
In Pasteur's time, scientists had a variety of opinions about spontaneous generation; many of the creationist catastrophist geologists accepted it while many evolutionists didn't. The last sentence of Darwin's Origin of Species reads:
"There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved."
This quote clearly demonstrates that the natural origin of life and evolution (that living creatures may exhibit "descent with modification") are two separate notions. The fact that there is much to learn about how the first living creatures originated has little to do with the truth or falsity of evolution. Thus an intelligent designer could have made the first forms and then they evolved. But, as I have previously discussed, that doesn't explain anything.
The modern scientific hypothesis that living creatures arose by a step-wise series of chemical interactions is so fundamentally different from the old idea of spontaneous generation that the British biochemist Pirie suggested that it be given a different name: biopoesis (Pirie, 1954, p. 43; Gaffron, 1960, p. 40).
Oparin's hypothesis is described in terms of seven assumptions. These assumptions are formulated by the Pandas authors, not Oparin, and several of them are superfluous or incorrect (3, 4, 6, 7) as will be discussed below. Although these assumptions state that various mechanisms "originated gradually" (presumably in stages), Pandas later criticizes the hypothesis (see section on problems with proteinoid microspheres) by discussing the unlikelihood that all the mechanisms arose instantaneously in their full complexity! Oparin did further experiments with various types of coacervates and discovered simple systems that could reproduce, carry out simple metabolic functions, mimic the electron-transport system or mimic photosynthesis (Dickerson, 1978).
Contrary to the assertion of Pandas, the geological evidence supports the fact that free oxygen was rare or not present in the atmosphere of the early earth. Sedimentary deposits older than two billion years contain no ferric oxides or other highly oxidized minerals. In fact, the evidence seems to indicate that the earth's oxygen atmosphere was produced by the activities of prokaryote photosynthetic organisms (Day, W. 1979, p. 74; Schopf, 1978, p. 60). Thaxton et al (1984, chapter 5) suggest that oxygen was present in the atmosphere at an earlier time based on the age of early prokaryote fossils judged to be photosynthetic. This would still put oxygen in the atmosphere at a time after the prebiotic chemical evolution phase of the origin of life. There is controversy about the exact nature of the early reducing atmosphere but a Urey-Miller type of experiment works just as well in atmospheres of various mixtures of gases—hydrogen, nitrogen, carbon monoxide and carbon dioxide—as long as free oxygen is not present (Dyson, 1985).
Pandas insists that "traps" did not exist on the primitive earth, but this is not true. For example, thunderstorms and lightning can occur at night. Amino acids and other monomers would be carried to the earth's surface in the rain where they might accumulate in shallow pools. Those under rocks, or in the interstitial spaces of the gravel, sandy or mud bottoms of the pools would be shielded from the ultraviolet rays of the next day. Also, only a tiny portions of the sun's output is at wavelengths shorter than 2,000 Angstrom units where it could be absorbed by such compounds as CH4, H2O and NH3. Possibly H2S, activated by the longer UV wavelengths, instituted synthesis reactions among these small molecules, the products then being washed into the oceans or freshwater bodies by rain (Fox and Dose, 1977, p. 78; Orgel, 1973, pp. 116-117). There, the more complex compounds would have been protected from the longer UV wavelengths. The primitive ocean would have been rendered even more opaque to UV by the layer of organic compounds near the surface (Miller and Orgel, 1974, p. 59). Recently it has been suggested that other sulphur compounds high in the atmosphere might have functioned similarly to today's ozone layer (Science News, 1988; 134(26,27):423). Ultraviolet light was not necessarily the major energy source for the prebiotic synthesis of organic compounds.
One remarkable fact about Miller-Urey type experiments is that, out of the thousands of possible compounds they could have produced, they produced relatively few substances and most of these are important compounds, amino acids, etc. found in all living organisms! And they are formed with surprising ease under prebiotic conditions (Orgel, 1973, pp.127-130; Miller and Orgel, 1974, p. 84; Fox and Dose, 1977, pp. 86, 141). Pandas' vision of tens of thousands of varieties of chemicals tying up useful chemicals in cross-reactions is incorrect. The large yields of "non-biological goo" mentioned on p. 5 has never been analysed, although there is evidence that it might be proteinaceous (Life Signs, 1984). Polymerization of the simple monomers would be facilitated by concentration caused by evaporation or freezing of the water or by the adsorption of the organic materials on clays. Fox (see below) polymerized mixtures of amino acids by drying and heating them (Dickerson, 1978).
Contrary to Pandas' assertion about the prevalence of "clay deposits of the time", early Precambrian sediments, unchanged by heating and metamorphosis, are rare. Many of those that do exist already contain microfossils similar to protein microspheres, representing early prokaryote organisms. The organic materials in these rocks have properties indicating a biological origin (Fox and Dose, 1977, pp. 292 fol.; Day, 1979, pp. 80 fol.). Many simple organic compounds are abundant in interstellar space and in comets. Organic material including racemic mixtures of amino acids (Fox and Dose, 1977, chapter 11; Miller and Orgel, 1974, chapter 15) and lipid-like organics able to self-assemble into membranes (Raloff, 1986) have been found in meteorites, indicating that prebiotic syntheses of organic monomers can and did occur in nature.
There are no biochemical reasons that the primordial living forms could not have been mixtures of the left- and right-handed amino acid forms, and that later, one form was selected by catalytic action of inorganic surface catalysts (certain clays) or biological enzymes (Dickerson, 1978, p. 36). Proteins can be made from racemic mixtures. Gaffron (1960, pp. 66, 72) discusses why forms using only one isomeric form of amino acids would be selected over those utilizing mixtures. Right-handed amino acids do occur today in certain bacterial proteins (Downes, 1962). Several right-handed amino acids (tryptophane, phenylalanine, methionine, histidine) will support growth in rats (West and Todd, 1951, p. 1151).
The results of hundreds of research projects over the last 30 years by scientists working in the field of protobiochemistry have established the following facts. Under very simple, straightforward circumstances, that must have been a common natural occurrence in the history of the earth, amino acids and nucleic acids do form from simpler common chemical compounds. The amino acids polymerize into peptides that in turn aggregate into larger, protein microspheres (protocell-like structures). All these steps occur by definite, deterministic (non-random) chemical processes (Fox, 1981b). Intensive study of the properties of the protein microspheres by many different protobiochemists have revealed that, while they are definitely not full-blown modern living cells, they exhibit many of the properties of living cells, including membrane structures with semipermeable properties, enzymatic activity associated with various metabolic reactions, synthesis of protein linkages as well as nucleic acid linkages, growth, excitability (neuro-electric phenomena similar to those in nerve cells), motility and conjugation (Fox, 1981a; 1984; Peterson, 1985).
We have already dealt with Pandas' assertion about many cross-reactions in dealing with their discussion of Oparin's assumption no. 3. One can form proteinoids very easily (high school students have done it in science fair projects). It is accomplished in the lab with heat and they are not destroyed. Only gentle heating is required. Furthermore, once they coalesce into microspheres they are very stable. Creationist criticisms of microspheres are dealt with by Fox (1984).
In judging the impossibility of the origin of a first protocell by natural means, Pandas consistently assumes that it must have the full complexity of a modern cell. This is about as intelligent as an aeronautical engineer insisting that a functional airplane must have the technological sophistication and complexity of a modern jumbo jet, thereby refuting the historical assertion that the first airplane was constructed in a bicycle shop. Certainly the first protocells were as simple and primitive relative to modern day cells as the Wright flyer was to a Boeing 747.
The present-day complex mechanism of protein synthesis was probably preceded by something much simpler. Some researchers think that the earliest protocells used RNA, because nucleic acid bases can polymerize into nucleic acids which reproduce themselves without the aid of the complicated enzyme systems found in modern cells (Beibricher, 1983; Eigen et al, 1981; Lewin, 1982b). Some RNAs even display catalytic properties (Cech, 1986). By further evolution, RNA molecules encoding protein enzymes aiding RNA reproduction could be added. The chemist D. H. White has shown theoretically that the simplest such self-replicating system or "autogen" consists of two RNA fragments, each encoding a simple peptide catalyst, one to assist in RNA replication and the other to drive the translation of RNA information into the peptides. The RNA chains could have been as short as 10 units (Garmon, 1981; Trachtman, 1984).
Other researchers postulate, because of the ease with which amino acids and peptides can be produced by abiotic means, that the first protocells contains protein only (like Fox's protein microspheres) and only acquired nucleic acids later for more efficient information storage and reproduction (Dyson, 1985). Could protocells based on proteins only have reproduced themselves by some autocatalytic process? There are some bacterial products that are noncoded peptides (Day, 1979, p. 369). Also there are infectious "virus-like" particles called prions, that are apparently devoid of nucleic acid (Dyson, 1984, p. 26 fol.; Prusiner, 1982; Prusiner, 1984). Nucleic acid particles may have entered into symbiosis with the protein protocells and subsequently specialized in information storage and protein synthesis—much like mitochondria and chloroplasts are thought to originated as symbiotic prokaryote organisms, eventually giving rise to the eukaryote cell (Margulis, 1974; Avers, 1989, pp. 115 fol.)
Enzymes could very well have evolved gradually and in stages. The earliest catalysts could have been metal ions (which function as cofactors for many modern enzymes, hydrous iron and manganese minerals (Science News 131(10): 152. March 7, 1987) or clay minerals that absorb organic materials on their surfaces. The enzyme catalase that catalyzes the decomposition of hydrogen peroxide to water and oxygen consists of a polypeptide attached to a heme (porphyrin) group that in turn contains ferric ion. The bare aqueous iron ion can catalyze the reaction but very inefficiently. Combining the iron ion with a heme group increases the catalytic ability by a thousandfold. Finally adding the polypeptide increases the catalytic function even further (Calvin, 1975). As we shall see in chapter 6 with respect to cytochrome c, there are many polypeptide sequences with the same functional properties and probably even more with similar properties. Thus any one of many polypeptides might have increased catalase activity; this being increased by natural selection of the more efficient variants during subsequent evolution. Waiting for a rare, unique polypeptide sequence to occur by chance is unnecessary. Even among present-day organisms, genetic variations of many enzymes are known (Koehn and Eanes, 1978).
The earliest cells were probably metabolically simple, getting all their necessary compounds from the prebiotic soup. As the supply of say, compound F dwindles, any cell with the capacity to synthesize it from a simpler precursor, E would have a selective advantage. When E becomes scarce, evolution of a new enzyme might allow some cells to use precursor D to make E and then F. By extension of such sequences, the step-wise development of more complex metabolism could have occurred (Avers, 1989, p. 82 fol.; Horowitz, 1945; Orgel, 1973, p. 174; Miller and Orgel, 1973, chapter 14). The evolution of new enzymes and enzymatic functions by mutation and natural selection has been demonstrated in bacterial cultures (Hall, 1982; Mortlock, 1982).
Cell membranes form spontaneously (self-assemble) like liquid crystals as a result of the chemical properties of their phospholipid molecules (Ambrose, 1982, p. 33). Such membranes will naturally absorb organic materials to form "protocells" (Trachtman, 1984). The biopoesis hypothesis asserts that living organization arose gradually in stages from very simple beginnings. It does not assert that modern-type cells with their great complexity arose instantaneously and spontaneously. That is what the intelligent design proponents (creationists) assert and they have no idea at all as to how it was accomplished! In fact they assert that it was a supernatural event forever beyond human understanding.
The key feature of photosynthesis is the photochemical splitting of water as a source of chemical energy to synthesize carbon compounds. Very simple coacervate drops containing chlorophyll can accomplish this and drive simple reducing reactions (Dickerson, 1978). Pandas' assertion that the process could not have developed by natural means is unjustified.
Pandas claims that there is a reasonable explanation for life's origin that has scientific support. It can't be intelligent design! We have already mentioned that this supernatural belief denies the possibility of understanding life's origin.
The embryogenesis of an organism is only vaguely like the process of building a house. The important and fundamental differences will be discussed below.
What scientific evidence exists to support intelligent design? The only direct evidence for intelligent design, spontaneous generation, has been disproved! Pandas claims that only intelligent design can yield amino acids of only one stereo isomeric form. I have already explained how that might have occurred naturally (see section above on the problems with the assumptions of the Oparin hypothesis).
Pandas doesn't discuss any weaknesses or problems associated with the intelligent design hypothesis (they obviously consider it perfect), so I will point out a few basic ones:
Their case depends on a questionable and logically faulty analogy. The analogy between organisms and manufactured articles is quite weak. Some manufactured devices do exhibit complexity, but they also display many fundamental differences from organisms that will be explored below. If the pickup truck left at the native village has, say, a sheep dog sitting in the cab—an animal we shall assume they never saw before—what would they conclude? That this animal was manufactured in some kind of celestial factory in the same way that they fabricate bows and arrows? Hardly. They would assume that it had been born of some appropriate parents! That is the proper conclusion following from an application of the "principle of uniformity." All organisms come from preexisting life. Pandas spent some pages disproving the possible exception (i.e. spontaneous generation). It is puzzling that the Pandas' authors should resort to David Hume's law of uniformity. Hume, in his book Dialogues Concerning Natural Religion, shows that the "Argument from Design," which is what Pandas is using here, is illogical and contrived. Norman Kemp Smith, late professor of Metaphysics at Edinburgh, in his introduction to Hume, explicitly points out the organisms are not like designed, manufactured objects (Hume, 1947, p. 102). Kaufmann gives his own brief version of Hume's argument (Kaufmann, 1958, section 45, pp. 114-115). Even Augros and Stanciu (1987), a book recommended by Pandas, makes this point (Augros and Stanciu, 1987, chapter 2). See the supplement: The Illogical Argument From Design, for further details.
Pandas claims that living cells are more like pickup trucks that microspheres! An internal combustion engine may not come into existence because of the physics of the metals from which it is made. But cell membranes do come into existence because of the chemical properties of the phospholipid molecules of which they are made. They are self-assembling, as are protein microspheres. Molecular self-assembly makes possible the chemical industry. Chemical are not manufactured by having workers screwing or bolting atoms together on an assembly line. No, the appropriate reactants are mixed in a vat under the appropriate conditions of concentration, temperature, pH, etc. and they assemble themselves into the product! There is no way DuPont can manufacture a chemical substance unless the atoms can be cajoled to form it on their own. The other structures of organisms come into being in similar fashion. Embryologists can watch closely the development of a frog or chick embryo. Structures form without the aid of artisans forming and assembling the parts. In this fundamental way organisms and protein microspheres are alike—their structures comes from the properties of the molecules of which they are made—and pickup trucks are quite different.
The nature of the information in DNA is not in the form of blueprints or specifications, but is more of the nature of a recipe (Dawkins, 1986, pp. 295 fol.). In development, appropriate substances are produced at the right time and these produce structures through their self-assembly. The genetic information can reproduce itself. In sexual reproduction, this information is reorganized into new forms. Note that in sexually reproducing species, no two individuals are identical (unless they are "twins" coming from the division of a single zygote—which is a form of asexual reproduction.) Manufactured items are all alike. You can't mix up the plans for two different automobiles and build a new car from them without a lot of engineers and mechanics making modifications.
The above considerations illustrate another fundamental difference between the reproduction of organisms and the production of manufactured items. The parts of the latter are formed independently of one another and only fit together on an assembly line because they were built to the specifications of a plan. The parts of an organism are formed during embryogenesis, in situ, where they can constantly interact with one another and adjust their sizes and shapes so that a functional organism results, even if that particular combination of genes produced at random from those of the two parents has never occurred before. Clearly intelligent activity is not needed in embryogenesis. Besides reproduction, organisms can repair themselves and grow and change by evolution. Even Pandas admits the reality of microevolution.
Given these facts and the principle of uniformity, it follows much more logically that the succession of fossil forms found in the sedimentary strata are descended from one another, rather than continually created anew by some kind of spontaneous generation (creation by an external intelligence) which has been proven not to occur in the present!
Modern ideas about the gradual step-by-step evolution of living things from nonliving components (which is not spontaneous generation) may not yet have come anywhere near answering all our questions about the process, but at least they involve hypotheses that can be tested and investigated by scientific means. A great deal of biogeochemical knowledge has resulted. (There is a journal, Origins of Life, devoted to publication of the results of biopoesis research.) None of this research has indicated that biopoesis is impossible. On the contrary, much of it has revealed how various necessary aspects of biopoesis might have readily come about along with tantalizing hints as to how protein synthesis and the genetic code might have arose! Also, such scientific research may have unexpected ramifications. The discovery that RNA could act as an enzyme was not only of great interest to scientists working on the origin of life but it led to the development of RNA enzymes to fight viral diseases (Radetsky, 1990). On the other hand, the intelligent design hypothesis has been around for several centuries and nothing has come of it! Until intelligent design proponents flesh out their vague, supernatural belief with testable ideas as to the nature of the designer(s) and how it (they) work, there will not and cannot be any scientific research along that line.
Pandas points out that Shapiro, 1986 (see Suggested Reading/Resources) gives a good critique of chemical evolution. He also provides a devastating critique of creationism. Good modern summaries of biopoesis research are given by Avers (1989), Kutter (1987) and Mason (1991). Older references are Day (1979), Orgel (1973), Miller and Orgel (1974). A more technical and biochemical review is given by Fox and Dose (1977).
Ambrose, E. J. 1982. The Nature and Origin of the Biological World. Ellis Horwood, Limited.
Augros, R. and G. Stanciu. 1987. The New Biology: Discovering the Wisdom in Nature. New Science Library of Shambhala Publications Inc.
Avers, C. J. 1989. Process and Pattern in Evolution. Oxford University Press.
Bassinger, D. and R. Bassinger. 1978. Science and the concept of miracle. Journal of the American Scientific Affiliation 30(4): 164-168.
Biebricher, C. K. 1983. Darwinian selection of self-replicating RNA molecules. Evolutionary Biology. 16:1-52.
Calvin, M. 1975. Chemical Evolution. American Scientist 63(2): 169-177 (March/April)
Cech, T. R. 1986. RNA as an Enzyme. Scientific American 255(5): 64-75 (November).
Dawkins, R. 1986. The Blind Watchmaker. W. W. Norton and Company
Day, W. 1979. Genesis on Planet Earth. House of Talos Publishers.
Dickerson, R. E. 1978. Chemical Evolution and the Origin of Life. Scientific American 239(3): 31-46.
Downes, H. R. 1962. The Chemistry of Living Cells. 2nd Edition. Harper and Row.
Dyson, F. 1985. Origins of life. Cambridge University Press
Eigen, M., W. Gardiner, P. Schuster and R. Winkler-Oswatitsch. 1981. The Origin of Genetic Information. Scientific American 244(4):88-119 (April).
Farley, J. 1977. The Spontaneous Generation Controversy from Descartes to Oparin. Johns Hopkins Univ. Press.
Fox, S. W. 1981a. From Inanimate Matter to Living Systems. American Biology Teacher 43(3): 127-135, 140 (March).
Fox, S. W. 1981b. Creationism, the Random Hypothesis and Experiments. Science 213: 290 (17 July).
Fox, S. W. 1984. Creationism and evolutionary protobiogenesis. In: Montagu, A. (Ed.) Science and Creationism. Oxford Univ. Press. pp. 194-239.
Fox, S. W. and K. Dose. 1977. Molecular Evolution and the Origin of Life. Revised Edition. Marcel Dekker Inc.
Gaffron, H. 1960. The Origin of Life. In: Tax, S. Evolution After Darwin. Volume 1. The Evolution of Life: its origin, history and future. University of Chicago Press. pp. 39-84.
Garmon, L. 1981. As It Was In The Beginning. Science News 119(5):72-74.
Gish, D. T. 1973. Evolution The Fossils Say NO! 2nd Edition. Creation-Life Publishers.
Hall, B. G. 1982. Evolution on a Petri Dish: The Evolved Beta-Galactosidase System as a Model for Studying Acquisitive Evolution in the Laboratory. Evolutionary Biology 15: 85-150.
Horowitz, N. H. 1945. On the evolution of biochemical syntheses. Proceedings of the National Academy of Sciences 31(6): 153-155.
Hoyle, F. and N. C. Wickramasinghe. 1981. Evolution from Space. Simon and Schuster.
Hume, D. 1947. Dialogues Concerning Natural Religion. Thomas Nelson and Sons, Ltd. (First printed in 1779. This edition edited with an introduction by N. K. Smith, late Prof. of Logic and Metaphysics, the University of Edinburgh)
Kaufmann, 1958. Critique of Religion and Philosophy. Harper and Bros.
Koehn, R. K. and W. F. Eanes. 1978. Molecular Structure and Protein Variation within and among Populations. Evolutionary Biology 11: 39-103.
Kutter, G. S. 1987. The Universe and Life: Origins and Evolution. Jones and Bartlett.
Lewin, R. 1982a. Where is the Science in Creation Science? Science 215: 142-146 (8 January)
Lewin, R. 1982b. RNA can be a catalyst. Science 218:872-874 (26 November).
Life Signs. 1984 (A note on the origin of proteins). Discover 5(6):11 (June).
Margulis, L. 1974. Five-Kingdom Classification and the Origin and Evolution of Cells. Evolutionary Biology 7: 45-78.
Mason, S. F. 1991. Chemical Evolution: Origins of the Elements, Molecules and Living Systems. Clarendon Press.
Miller, S. L. and L. E. Orgel. 1974. The Origins of Life on the Earth. Prentice-Hall, Inc.
Morris, H. M. 1963. The Twilight of Evolution. The Craig Press.
Morris, H. M. 1967. Evolution and the Modern Christian. The Presbyterian and Reformed Publishing Co.
Morris, H. M. 1972.The Remarkable Birth of Planet Earth. Institute for Creation Research.
Morris, H. M. (Editor). 1974. Scientific Creationism. Creation-Life Publishers.
Mortlock, R. P. 1982. Regulatory Mutations and the Development of New Metabolic Pathways by Bacteria. Evolutionary Biology 14: 205-268.
Oparin, A. I. 1953. The Origin of Life. 2nd Edition. Dover Publications.
Orgel, L. E. 1973. The Origins of Life: Molecules and Natural Selection. John Wiley and Sons.
Peterson, I. 1985. Proteinoids: Clues to Cellular Origins? BioScience 35(2):74-76. (February).
Pirie, N. W. 1954. On Making and Recognizing Life. New Biology 16: 41-53.
Prusiner, S. B. 1982. Novel Proteinaceous Infectious Particles Cause Scrapie. Science 216: 136-144. (9 April).
Prusiner, S. B. 1984. Prions. Scientific American 251(4): 50-59 (October).
Radetsky, P. 1990. Genetic Heretic. Discover 11(11): 78-84 (November).
Raloff, J. 1986. Clues to life's cellular origins. Science News 130(5): 71 (August 2)
Shapiro, R. 1986. Origins: A Skeptics Guide to the Creation of Life on Earth. Bantam Books.
Schopf, W. 1978. The Evolution of the Earliest Cells. Scientific American 239(3): 48-64.
Thaxton, C. B., W. L. Bradley and R. L. Olsen. 1984. The Mystery of Life's Origin: Reassessing Current Theories. Philosophical Library.
Trachtman, P. 1984. The Search for Life's Origins — and a first ‘synthetic cell' Smithsonian 15(3):42-51 (June).
West, E. S. and W. R. Todd. 1951. Textbook of Biochemistry. Macmillan Co.
White, A. D. 1960 (1895) A History of the Warfare of Science with Theology in Christendom. Dover Pub. in 2 vols.
(from Frank Sonleitner's critique of Of Pandas and People)
Outline of the Pandas Chapter
Darwin was always aware of the difficulties that blending inheritance would cause for natural selection but he was also aware of other evidence, prepotency or dominance and reversion, which presaged Mendel, along with the ubiquity of individual differences which animal and plant breeders used so effectively.
Darwin makes no mention of a mechanism of heredity in the Origin of Species. In fact he states in chapter one that the laws of inheritance are unknown (Darwin, 1968, p. 76). He did assume that there was a hereditary mechanism and individual differences, and since they were compatible with the operation of artificial selection as practiced by animal breeders, they must be compatible with the operation of natural selection (Darwin, p. 63, Modern Library Edition of the Origin). After reading in 1867 Jenkin's criticism that random variation would not be sufficient to replenish the variation lost through blending inheritance, Darwin gave added weight to use and disuse and Lamarckian effects of the environment as mechanisms producing variation and downplayed the importance of "single variations", what we would call mutations (see Denton, 1986, p. 63 fol.; Vorzimmer, 1970, chapter 5; Darwin, p. 71 Modern Library Edition of the Origin). In his 1868 work, The Variation of Animals and Plants under Domestication, Darwin introduced his hypothesis of pangenesis where every part of the body produced heredity particles or "gemmules" which circulated throughout the body, aggregating in the gametes to be transmitted to the next generation where, during development they produced a new individual. In some cases they might remain dormant for generations (Moore, 1957, pp. 148-159.)
Mendel's principles are presented quite accurately but their consequences for evolution are not! As we have seen above, Darwin did not have his own theory of blending inheritance (Pandas, bottom of column 2, p. 60) but one of particulate inheritance. Why should knowledge of Mendelian inheritance lead Darwin to Blythe's view of selection as exclusively a conservative force? It is blending inheritance that produces a phenomenon similar to conservative or stabilizing selection. Mendelian inheritance, on the other hand, preserves new traits (even Pandas says so, top of column 1, p. 61) that are generated by mutation, thus allowing natural selection to act upon favorable ones just as Darwin believed (Denton, 1986, p. 64). Pandas' argument here is an example of totally muddled logic! Mendel was an ardent Darwinian!
Micro- and macroevolution are two ends of a continuous scale of phenomena with speciation in the middle. Some authors consider speciation as microevolution and others as macroevolution. Microevolution can be studied directly in terms of genetics and natural selection working on populations. Macroevolution is usually studied from the fossil record and hence involves different methodologies. Almost all evolutionists think that macroevolution is based on microevolutionary processes and involves no new or unknown principles. The ideas of punctuated equilibrium and species selection are applied to the origin and proliferation of new taxa and developmental processes are studied to shed light on the evolution of major structural changes (Ayala, 1983; Eldredge, 1989, chapter 1; Gould, 1983; Hecht and Hoffman, 1986; Levinton, 1983; Maderson, 1982; Stanley, 1979, pp. 2 fol.; chapter 7).
The nature of the protein-assembling information stored in structural genes is restricted to the amino acid sequences of polypeptides. Once the polypeptides are synthesized on ribosomes, they self-assemble into their characteristic three dimensional shapes and unite with other polypeptide chains to produce the secondary, tertiary and quaternary levels of structure associated with that particular protein. Other genes, called regulatory genes are involved in "turning on and off" the various structural genes at the proper times during development. Thus, the DNA does not carry a "detailed plan" or blueprint of each protein molecule, only the amino acid sequence, which when fabricated, will self-assemble into the protein molecule.
We have already discussed the appropriate application of Hume's principle of uniformity in the previous chapter. Unlike the blueprints of engineers, DNA contains a recipe (Dawkins, 1986, p. 295 fol.) for making an organism, some parts of which are duplicated many times, some parts of which contain much "nonsense" information—hardly what one would expect from an "intelligent" designer. Recent discoveries, for example, have shown that a gene consists of sections called exons and introns. After the formation of messenger RNA, the introns are excised out. The non-coding fraction may be large—as much as 95% in the case of the beta-like globin genes in humans (Avers, 1989, p. 141 fol.) In general, coding sequences make up only a small part of the total DNA and the great bulk is largely a neutral and randomly drifting sink made up of pseudogenes, silent redundancies, introns, repetitive sequences, retrovirus DNA and transposable elements! (Britten, 1986; Carson, 1989).
According to Pandas, many biologists in the late 19th and early 20th century held the misconception that dominant traits would become more common with the passage of time. This is untrue! Provine, in his history of evolution and genetics of that period makes no mention of such a belief (Provine, 1971). Hardy was prompted to write his paper by a comment made by the statistician Udny Yule. In the discussion following an address in 1908 at the Royal Society of Medicine on "Mendelian Heredity in Man" given by the geneticist R. C. Punnett, Yule asked why dominant characters were not becoming increasingly common in the population. Punnett knew Yule's apparent expectation was wrong, but didn't know why and asked Hardy for help (Hardy, 1908, referred to by Pandas footnote 1; Provine, 1971, p. 133; Punnett, 1950, p. 9). Thus Pandas has the argument backwards! It is not quite clear what Yule was thinking when he made that query; previously he, in 1902 and later the biometrician Karl Pearson in 1904 had derived the Hardy-Weinberg law for the special case where the initial allelic frequencies were 0.5. Had they generalized their results for any allelic frequencies, we might very well today be discussing the Pearson-Yule Law (Provine, 1971, pp. 81, 133).
The Hardy-Weinberg states that allelic frequencies of a particular gene locus will remain unchanged from generation to generation unless changed by mutation, natural selection, migration, or random drift. If one further supposes random mating, the laws predicts the genotype frequencies (Avers, 1989, pp. 253 fol.; Futuyma, 1986. p. 82 fol.). Discovering Hardy-Weinberg disequilibrium in genotype frequencies is often a sign that various organizing factors are at work (Futuyma, 1986, p. 99).
Intelligent design proponents assume that in the beginning (they can't even agree as to when that was—see Pandas, p. 92) all basic types of organisms (they can't identify what these basic types were—see Pandas, p. 78) were given a set of genetic instructions (by means totally beyond our comprehension)—a highly uninformative statement to say the least!
Mutations occur and reoccur at a characteristic rate for each gene. Back (reverse) mutations also occur at characteristic rates (Avers, 1989, p. 163). They are random in the sense that the chance that a specific mutation will occur is not affected by how useful that mutation would be (Futuyma, 1986, p. 76). Most mutations are recessive and in a sexually reproducing population, instances of a mutation will accumulate reaching a steady state when the number of reverse mutations equals the number of forward mutations. Thus a species population contains a large number of mutations, each existing at a low frequency in the population, which can be used as raw material by natural selection if and when the environment should change.
The analogy between DNA and words in a book is very weak. All individuals in a population carry a few mutant genes. Human individuals probably differ from each other at as many as 5 million sites and new genomic difference appear by the hundreds with every birth (Britten, 1986). Also, as we have remarked above, DNA contains a lot of nonsense material. If books were like DNA, not only would the words be separated by nonsense sequences but the words themselves would have nonsense sequences (introns) inside them. One would hardly expect an "intelligent author" to write such a book! One must always question arguments whose conclusions depend upon weak or unsatisfactory analogies! Whether a mutant gene is an improvement or not depends upon the environment in which the individual is living. Human populations with high frequencies of the sickle-cell gene only occur in areas where malaria is prevalent. Penicillin-resistant strains of bacteria only appeared after the use of penicillin became widespread. If malaria were eliminated or the use of penicillin discontinued, these genes would be selected against. This has already happened to some extent with regard to the sickle-cell gene in the black descendants of African slaves in the United States (Avers, 1989, p. 227). There are many examples of drosophilid mutants whose fitness depends upon the environment; there are also a number of research studies on drosophilids demonstrating that mutations may increase fitness of populations (Dobzhansky et al, 1977, pp. 64, 66).
Evolution is "descent with modification" and does not necessarily involve additional complexity. And of course, mutants can not be selected for some future utility, although, as was mentioned above, every population has a store of mutant variation, some of which might prove useful if the environment changes. Pandas' statement that "it has not been demonstrated that mutations are able to produce the helpful traits and structures needed for the development of a new species" illustrates the confusion and misunderstanding of evolution existing in the minds of its authors. Natural selection will select genotypes that have increased probability of surviving and reproducing. New species are produced when populations are isolated from one another and they can no longer interbreed. In drosophilids many example of "sibling species" are known. These are species that are morphologically identical, but yet cannot interbreed.
Although most mutations that are large enough to be conspicuous are harmful, most mutations are neutral in effect (Britten, 1986). The existence of back or reverse mutations are uncontestable examples of beneficial mutations and show that the "wild-type" genes could have originated by mutation. The commonly-used Ames test for detecting carcinogenic (mutagenic) substances depends on the occurrence of such beneficial reverse mutations (Maugh, 1978). Exhaustive tests have shown that 90% of the time the Ames test will give positive responses to a mutagenic chemical! There are well-documented experiments with microorganisms where new enzymes have arisen by mutation (Clarke, 1974; Hall, 1982; Mortlock, 1982). Many of the newest "Green-Revolution" crop-plant strains have been bred from radiation-induced mutants (Sigurbjornsson, 1971).
Natural selection is differential survival and reproduction, a perfectly operational definition that can be simulated in a computer model and investigated mathematically. We shall investigate proof of its "creative" powers later. For a pair of authors so enamored of information theory, the Pandas' authors seem incapable of understanding that the intelligent design argument (i.e. creationism!) has no information content. They offer nothing concerning what the designers are, how they work, etc. New organisms just appear out of nowhere!
If the intelligent designers wanted quality control, why did they endow virtually all eukaryote organisms with sexual reproduction that is continually producing new gene combinations at the expense of old? There are various DNA copy-error correcting mechanisms in the cell. Why couldn't these wonderful designers produce one that would eliminate all mutations? There are genes known to affect the replication mechanism and elevate mutation rates. Such genes are rare in natural populations but have not been completely eliminated suggesting that mutation rates may have evolved to an optimum level (Futuyma, 1986, pp. 72-74, 259). In certain selection experiments with bacteria, such "mutator" genes may increase in frequency giving such asexual clones an advantage because their genetic variability stems directly from new mutations (Futuyma, 1986, pp. 259-260).
Natural selection is the result of the action of the environment upon the individuals of a species. If the species is already well adapted to the environment and the environment is stable, it will subject the population to stabilizing selection. If on the other hand, the environment is changing, it will exert directional selection upon the population. In the last century and a half, most environmental changes have been due to the activity of man and directional selection has been observed in regard to industrial melanism in many species of lepidopterans including the famous peppered moth, pesticide resistance in insects, drug resistance in microorganisms, etc. (Futuyma, 1986, p. 158).
Pandas ignores the many documented cases of directional selection, but of all the cases of stabilizing selection that they could have cited (see Mayr, 1963, p. 282 fol.) the "classic" paper by Bumpus (Bumpus, 1898) is a poor example which suffers from several basic and fatal logical and statistical flaws (Robson and Richards, 1936. pp. 209-211). Bumpus studied a sample of sparrows that had been "blown down" by a sudden storm. These particular birds most likely fell victim to the storm because they were in open, exposed places when the storm struck and not because some subtle differences in morphology made them more susceptible. Thus this sample of birds probably has little relevance to the question of stabilizing selection in nature. Also, it is very likely that they all would have died if they had not been rescued and cared for in the laboratory. Thus the meaning of any differences found between those that survived and those that died is hard to assess. It took sophisticated statistical techniques to find significant differences between a few of the measurements on this sample of birds which supported Bumpus' conclusions! (Harris, 1911; Calhoun, 1947; Johnston et al, 1972; Grant, 1972; O'Donald, 1973).
This celebrated case of directional selection is a phenomenon involving the appearance of melanic forms in hundreds of species of moths following the discoloration of tree trunks due to air pollution produced by the industrial revolution in Europe and North America. These moths are night flyers and rest on tree trunks during the day. They are cryptically colored to protect them from predation by birds (Kettlewell, 1959; Kettlewell, 1973; Bishop and Cook, 1975).
The black gene producing melanism in the peppered moth may have been already present at low frequencies in that species population, but this is not so of many other species of moths that became melanic due to industrial pollution. These had to wait for rare mutations to take place. There was a lag of 100 years and more before the first record of a black form in Brachionycha sphinx and Xylocampa areola. Melanism has not yet appeared (1973) in Graptolitha ornitopus in Britain although all the related species in North America have distinct dark forms. In Biston betularia (the peppered moth) there has also been selection for modifier genes to increase the dominance of the black gene and make the black forms blacker than they were in the 19th century (Kettlewell, 1973, p. 313 fol.). Other genetic changes improving the viability of the black forms have occurred. "When moths of the dark form were crossed with moths of the light form 50 years ago, the resulting broods were significantly deficient in the dark form. When the same cross is made today, the broods contain more of the dark form that one would expect." (Kettlewell, 1959). Also, the moths tend to select surfaces of the same color as themselves upon which to alight and rest. Thus industrial melanism is much more than a simple change from light to dark. Lovtrup (1987, p. 319) also holds this view.
Ambrose' argument (Ambrose, 1982, Pandas' footnotes 2, 3, 4, and 6, referring to pp. 120, 123, 143 and 140-141 respectively) against the formation of new structures is based on several wrong-headed assumptions. First of all, Ambrose assumes that the new genes or mutations are neutral, totally without selective value, until their combination occurs. Thus he eliminates the possibility that natural selection could aid in forming the combination! In his example with five gene mutations, he can only imagine the impossibility of their ever coming together by chance. Yet Haldane gives a similar example using 15 genes. If each of these is only slightly favored by natural selection, they will all increase in frequency in the population and eventually all 15 will regularly occur in the same organisms. Haldane's argument will be discussed in more detail below. Secondly, Ambrose assumes that these are totally new genes, in no way integrated into the developmental system and so for the combination to be expressed, new regulator genes, etc. must be introduced. But all known "new" genes derive from mutations or duplicates of already existing genes. Such will hardly be totally "neutral" in effect and will automatically be subject to the regulator gene of the original structural gene. Evolution of new enzymes and metabolic pathways in experimental populations of bacteria have been reported and they arise by modification of existing pathways (Mortlock, 1982; Hall, 1982). Our knowledge of the evolution of regulatory genes is summarized by MacIntyre (1982).
Thus Ambrose' argument, which starts from wrong-headed assumptions about the Darwinian mechanism of evolution, cannot help but come to incorrect and irrelevant conclusions. Dressing up his argument in concepts from information theory cannot make up for wrong starting assumptions!
Truly "new" structures can only arise with difficulty by the mechanism of mutation and natural selection because of all the concomitant systems, nervous, circulatory, skeletal, muscular, etc. that would have to arise. But we observe very few truly new or novel structures in nature (Futuyma, 1986, p. 410; Mayr, 1960; Mayr, 1963, pp. 602-621). Wings don't sprout out of the backs of flying animals as in the mythical Sphinx, Pegasus and angels. No. The wings of birds, bats and pterosaurs are modified forelimbs. They operate with the nerves, muscles, blood vessels, etc. that were already present. Thus we find this incredible conservatism of "design" that has no parallel in human intelligent design—nearly all "new" structures are modifications of old ones. This is what you would expect from natural selection. It acts as a tinkerer, rather than a designer (Jacob, 1977). This is the evolutionary explanation for the ubiquitous, all-pervasive homologies that characterize the myriads of forms in each of the phyla and which were recognized by the 18th and 19th century pre-evolutionary anatomists (see the discussion in Excursion chapter 5 which deals with homology.)
Darwin was referring to this phenomenon when he referred to ". . .nature prodigal in variety but niggard in invention. . ."(Darwin, 1968, p. 445). Thus the "design" of animals shows incredible conservatism. The limbs of all vertebrates have the same set of component bones and muscles, yet they perform diverse functions—running, flying, swimming, digging, etc.. An engineering school that demanded that engineers design auto wheels, airplane wings, boat propellers, and excavation buckets from the same set of basic parts would be considered crazy. Similarly, the same set of insect mouthparts are modified for chewing and grasping like pliers, piercing and sucking like hypodermic needles or sponging and lapping like a vacuum cleaner. In development, terrestrial vertebrates produce gill pouches, clefts and arches and modify them for other functions.
Even insect wings show little that is truly "new." The wings themselves derive from lateral extensions of the dorsal tergal sclerotized plates. The muscles that flap the wings are modified body wall muscles, while the muscles that steer the wings are modified leg muscles (Snodgrass, 1935, 1958)! The incipient "paranotal" lobes that eventually evolved into wings may originally have had a thermoregulatory function, that is, the slightest increase in body surface area would allow the insect to warm up faster in the morning when the sun's rays struck it (Lewin, 1985; Gould, 1985).
The rod and cone sensors of the retina of the vertebrate eye are modified cilia of cells that formerly lined the interior of the hollow nerve cord. In the tiny transparent invertebrate ancestors of the vertebrates, it didn't make much difference that the "eyespot" was in the center of the body but as the vertebrates grew larger and the eye became a stalked cup projecting from the nerve cord so that it could be close to the surface of the body, its basic geometry resulted in the retina being functionally backwards with the sensory cells at the back and the nerve fibers and ganglia connecting them to the brain between them and the lens (Berrill, 1955, chapter 20). For a more general discussion of the evolution of photoreceptors and eyes, see Eakin (1968) and Salvini-Plawen and Mayr (1977).
This biological conservatism even extends to genes. Genetic studies have shown that "new" genes often arise through duplication of existing genes and then change their functions through mutations. Evidence from protein structures shows that some genes can perform more than one function without any changes. For example the various crystallin proteins that form the lens of the eye double as enzymes! A crystallin from birds and reptiles is identical to an enzyme in the urea cycle. Another from turtles is the same as a enzyme involved in sugar breakdown. A third from ducks and crocodiles is the same as the lactate dehydrogenase enzyme (Marx, 1988).
But all "new" structures can't have come from pre-existing structures. Somewhere in the evolutionary history of a group, novel structures undoubtedly arose. But they were very simple and had their origin very early in evolution, such as the paired limbs of vertebrates (Futuyma, 1986, p. 410). Or the vertebrate eye—the complex vertebrate eye begun as a few light-sensitive cells in the spinal cord to the Tunicata, the presumed invertebrate ancestor of the vertebrates. The eye then evolved through a series of stages, each functional and useful to its bearers: a simple light-sensitive stage; a directional light-sensitive stage once pigment cells partially surround the organ; a simple lens formed from the epidermis concentrating the light on the sensory cells increased the eye's sensitivity in dim light; proliferation of the sensory cells allowed for detecting shadows and large dark shapes; refinement of this organ led to the present-day camera type eye (Berrill, 1955, chapter 20). This "changing function" hypothesis explains how natural selection can govern the origin and evolution of a new structure without macromutations. It also explains some of the remarkably peculiar design flaws of the vertebrate eye, such as the backwards-retina and the blind spot. No sane electronics engineer would ever dream of designing a television camera the same way the vertebrate eye is organized! The peculiar "design" features of many complex organs is powerful evidence that they were fashioned by natural selection and not by an intelligent Creator.
All these facts and many more support the idea that "new" organs and structures evolved by natural selection and each of the "stages" were functional, although the functions themselves changed during the course of evolution.
According to Pandas, discoveries have been made that question the evolutionists' belief that the giraffe's long neck functions for browsing in trees. Fossil giraffes are found side by side with fossils of sheep which are grazers, female giraffes are shorter than males and giraffes in zoos are observed to eat grass. Pandas would have us believe that giraffes really use their long necks to reach the ground to eat grass and drink water! This inane idea is quoted almost word for word (but not cited) from Taylor (1983, p. 40.) Taylor was a science writer and his book contains a number of other unbelievably incorrect "facts."
Presumably the giraffe's long neck is necessitated by its long legs. But why do giraffes have long legs? Was it a whim of the intelligent designer? Certainly it is not so that they can run fast. Top running speed of a full-grown giraffe is only about 35 miles per hour. Almost all the antelope that share the African savannahs with the giraffe can run faster! So why do they have long legs? Furthermore, if the function of the long neck is to reach the ground, then the intelligent designer didn't do a very intelligent job of designing. The giraffe's neck is not quite long enough to reach the ground! In order to do so, a giraffe must assume an awkward posture with its forelegs spread out and/or bent. (The very young of many ungulates have the same problem. Their disproportionately long legs enable them to keep up with their mother if they must flee from danger.) Giraffes only need to reach the ground to drink. Interestingly enough, their drinking habits are quite variable. Some populations appear to drink regularly while others rarely drink (if at all) as long as green browse and shade are available.
Giraffes are browsers able to feed on leaves up to 5 meters above the ground. In areas of the African savannahs where giraffe herds feed, there is a noticeable "browse line" on the acacia trees at a height of about 5 meters. No other browsing animals can reach above 2 meters except for elephants and they are just as likely to knock down a tree to get to its high branches. A newborn giraffe is about 2 meters tall and although they may nurse for up to two years, they normally begin browsing at about one month of age. Thus giraffes, because of their height, have access to a food supply not available to other ungulate herbivores. Male giraffes fight by hitting each other with their necks to determine their position in the social dominance hierarchy and who shall have first chance to mate with the females. Thus larger size may give a selective advantage to males. The height difference between males and females may also lessen feeding competition between them and lead to more uniform browsing at the complete range of browsing heights (du Toit, 1990).
When trees are overbrowsed, giraffes may feed on smaller bushes. In one instance in Nairobi National Park, the feeding activities of giraffes reduced height of whistling thorn bushes from 120 cm high to 67 cm high and producing an "inverse browse line". Giraffes are obviously adapted for reaching high rather than low. They really are browsers and Pandas' arguments against the idea that the long neck (and the long legs) allow the giraffe to reach leaves high above the ground are logically and biologically untenable. (See Dagg and Foster, 1976 for everything you ever wanted to know about giraffes).
But what about the complicated adaptational package of the giraffe? When a giraffe lowers its head, would the increased pressure due to the weight of the blood in the neck burst the blood vessels? No. Any increased blood pressure is counterbalanced by a similar increase in pressure in the surrounding extracellular fluids bathing the body tissues (Warren, 1974, p. 99). This same mechanism prevents blood vessel distension and edema at the bottom of the long legs. The giraffe does face the need to pump blood to the head which may be 7 to 10 feet above the heart when the giraffe is standing erect. To accomplish this the giraffe's heart generates a high blood pressure averaging 260/160 mm Mercury compared to the 120/80 average for a resting man (Warren, 1974, p. 98). But what about the pressure sensors, the rete mirabile, etc.? All mammals have arterial pressure sensors in the neck, usually located in the carotid sinus; all have valved veins (even human have valves in the jugular veins (Schaeffer, 1953, pp. 751, 762.); most if not all ungulates have a rete mirabile (Dagg and Foster, 1976, p. 168); the shunt between the carotid and vertebral arteries also occurs in other ungulates, including the short-necked relative of the giraffe, the okapi, although it is not as large as in the giraffe (Lawrence and Rewell, 1948). These all function to assist in the circulation of the blood, not to prevent bursting blood vessels. In the evolution of the giraffe's "adaptational package", no "new" structures had to be "invented", only old ones already present were modified to adapt to the giraffe's high blood pressure. This is the hallmark of natural selection, which can acts to improve or modify the functioning of pre-existing structures, although they eventually may be modified so drastically that the results may look like new, unique products. Even the lengthening of the giraffe's neck involves no "new" structures. For example, it still has only seven cervical vertebrae, the same number as in humans and all other mammals—except a few tree sloths with six or nine (Romer, 1949, p. 159).
The design proponents insist that only a "consummate engineer" could have anticipated the engineering requirements of the giraffe. How is it then that this "consummate engineer" missed a requirement as simple as giving the giraffe a neck long enough to reach the ground without engaging in postural contortions? Also, giraffes, like other large ungulates, have to spend most of their waking hours feeding because they rely on inefficient bacterial fermentation to digest their food—the "consummate engineer" neglected to endow them with enzymes for breaking down cellulose and lignins!
The stone plants: One way to adapt to dry, desert-like conditions is to reduce transpiration and evaporation of water by reducing the surface/volume ratio of the body by acquiring a spheroidal shape—which also happens to be the shape of a pebble. Is this "design sophistication" that requires an intelligent designer? Hardly.
But can "the blind, chance forces of nature produce what distinguishes such intelligent human beings?" This is a loaded question because the neo-Darwinian mechanism of evolution is not a mechanism of blind, chance forces. It has four basic components:
The last three components mold successful gene combinations from favorable mutations to produce better adaptations. They act as a strongly non-random and creative mechanism. When all four of these elements are included in a mathematical model or computer simulation program of evolution, it works! (Dawkins, 1986; Dewdney, 1989 a and b). The typical creationist endeavor along these lines however, only considers one of these elements, namely mutation (Bliss, 1976, pp. 47-49; Morris, 1974, pp. 59-69). Ambrose' argument (along with that of Edens, 1967) falls in this same category. Thus from the biological point of view, their calculations assume that all the mutations of some new trait or new species, arise simultaneously or in sequence in a single individual. The occurrence, anywhere along the line, of a single deleterious mutation negates the entire endeavor. This, of course, is not evolution, but instantaneous creation by purely random processes. It's no wonder the creationist version of evolution doesn't work.
For evolution to occur the other three elements are necessary. Even the most finely crafted automobile won't go very far when three of its four wheels have been removed! In a population the occurrence of a lethal mutation affects only the individual possessing it. Reproduction by normal individuals replace those killed by lethal mutations and conserve what evolutionary progress has been made. Deleterious mutations may be passed on to offspring but are eventually weeded out by natural selection. On the other hand favorable mutations spread through the population under the action of natural selection. Finally, genetic recombination insures that favorable mutations arising in different individuals will eventually be combined in descendent generations.
All the major taxonomic groups of eukaryote organisms have sexual genetic recombination. This is in addition to whatever asexual reproduction a group may possess. Those instances where sex is absent are apparently secondary losses. A variety of phenomena (transduction, etc.) bring about genetic recombination in prokaryotes. Recombination results in genetic diversity and the developmental systems of eukaryotes have mechanisms (ex: induction) for coordinating the production of a functional individual from diverse genetic messages. These mechanisms can also accommodate mutations that do not produce too drastic a change.
Haldane gives an example to show the creative power of selection which is similar to the situation posed by Ambrose (Haldane, 1932, p. 95; Haldane, 1936, p.67; see also Keeton, 1972, p. 594). Suppose that in a particular population there are 15 rare mutant genes. Each occurs in only 1% of the individuals in the population. The probability that all 15 would occur together in one individual as the result of random sexual recombination is vanishingly small. But even if there is only moderate natural selection for each of the 15 genes, in only about 10,000 generations each will have increased from a frequency of 1% to a frequency of 99% of the population. At this time, 86% of the population can be expected to have all 15 of these genes and display a phenotype that was previously nonexistent in the population. Thus natural selection can take mutations and mold them into combinations of high adaptive value, just as the painter, who didn't make either his canvas or paints, creates combinations of shapes and colors on the canvas that are pleasing to our eyes.
With the availability of fast, powerful computers and computer simulation techniques, even engineers (the prototypical intelligent designers!) are using the creative powers of natural selection to aid them in their design efforts. The technique of "genetic algorithms", pioneered by computer scientist John H. Holland at the University of Michigan, simulates the mechanism of Darwinian evolution, involving mating, genetic recombination, reproduction, selection and mutation to design jet engines, integrated circuit chips, scheduling work in a busy machine shop, operating gas-pipeline pumping stations and recognizing patterns (Peterson, 1989).
Random variations on the specifications for a device are encoded on "chromosomes" of "individuals". The computer evaluates the properties of each individual and the "fitter" one are allowed to mate; "genetic recombination" of chromosomes and even "crossing-over" takes place and a new generation of individuals is produced. Thus each new generation is created from the best pieces of the previous one. This approach efficiently and rapidly zeros in on the best design or solution to a problem. "Mutation" operations are often introduced to keep the process from getting stuck at a suboptimal answer because of a poor choice of starting configurations.
David E. Goldberg, an engineer at the University of Alabama and author of the book, Genetic Algorithms in Search, Optimization, and Machine Learning (1989, Addison-Wesley) reports that genetic algorithms work in lots of different problems but there is still room for improvement by incorporating artificial analogues of other evolutionary and genetic mechanisms. Creationists always claim that evolution can't possibly work. Yet here are engineers (no less!) using EVOLUTION TO DESIGN things. With all the evidence for evolution, could this is the non-supernatural mechanism used by the intelligent designers?
The quotation from Ambrose again shows that author's ignorance of the nature of the environment-organism interaction which is natural selection. The environment does not ask "simple yes or no questions" of the organism, it "selects" those that are better adapted to survive and reproduce in that environment. The English sparrow example discussed below shows the power and subtlety of natural selection. Pandas claims that natural selection works with already-existing genes. But those variant genes, at one time in the past, arose by mutation. (Presumably Pandas would claim that they were all supernaturally created.) Because any particular mutation is recurring at some characteristic rate, we cannot rule out the possibility that North American English sparrows possess mutations acquired since the species was introduced into the New World and that one or more of these are incorporated into the gene combinations selected. Next to nothing is known about the genetics of English sparrows. There is only indirect evidence that the geographic differences in body size and shape have a genetic origin (Johnston, 1973; 1975). Pandas' example of multiple gene loci producing a quantitative gradational character such as skin color may or may not represent the genetic basis for the observed differences in the sparrows. Again, changing from one species to another involves the evolution of interspecies sterility which is appropriately discussed in connection with Chapter 3.
House sparrows were introduced into North America several times between 1850 and 1881 from sources in central England along with some birds from Germany. Once they became established, many transfers of sparrows (80 by 1880) were made from the original sites of introduction to other parts of the country (mainly eastern states but also San Francisco and Salt Lake City) where they were fed and protected. In this fashion, along with the rapid expansion of their range by the birds themselves, they came to occupy most of the continental United States by 1900 (Summers-Smith, 1963, p. 175 fol.; Calhoun, 1947; Johnston and Selander, 1971).
Although earlier workers (Lack, 1940; Calhoun, 1947) investigated geographic variation in these birds, the first extensive investigations were carried out and reported by Johnston and Selander in a series of papers beginning in 1964. They found conspicuous differentiation in color and size. The color differences conform with Gloger's ecogeographic rule, which related color to regional variations in temperature and humidity. Specimens from northern and Pacific coastal localities and the Valley of Mexico were dark; those from the arid southwest were pale; those from the midwest were intermediate in shade. These color differences are not subtle average differences, but marked and consistent (Johnston and Selander, 1964; Halyard, 1965).
Measurement of a number of skeletal characters show a gross size factor with strong negative regression relationships with winter temperature, consistent with Bergmann's ecogeographic rule (larger forms are found in colder climates). They also exhibit a pattern of relative size between body core and limbs, consistent with Allen's ecogeographic rule (forms with smaller extremities—ears, limbs—are found in colder climates). Both of these rules are explained on the basis of the role of body surface/volume ratio in heat loss and retention (Johnston and Selander, 1971). Similar selection pressures resulted in the differences between the Eskimo and African mentioned by Pandas.
Variation within any local population is similar throughout the range in North America and similar to that in England and Germany. Variation between populations is less than that occurring throughout Europe, even though the North American forms cover a much wider range of climate. This is also true for the range in values exhibited by each character. This is probably due to the limited number of generations upon which selection has had the opportunity to act along with the relatively little interpopulation variability in the English and German birds making up the source stock of American sparrows. On the other hand, the character ranges of the North American males exhibit equal or exceed those for the English-German samples. North American females match or exceed the English-German samples in only five of the sixteen characters studied (Johnston and Selander, 1971). Few genetic data are available for the house sparrow, but electrophoretic studies show that the sparrows exhibit relatively little polymorphism (Johnston and Klitz, 1977).
The sparrows are an excellent illustration of the power of natural selection to create new combinations of characters subtly adapted to new environmental conditions. This is directional selection changing the species, not conservative, stabilizing selection.
At the end of this section, Pandas tries to convince us that directional selection does not occur, that it is exclusively a conservative and not a creative force. But the sparrow example shows otherwise. Natural selection has created new gene combinations that are better adapted to the extremes of climate found in North America. The species has been preserved by being changed. Pandas admits this on the preceding page where the authors say that natural selection provides a means for a species to establish new niches and to adapt to changing environments. And it does this by changing the species. The changed species is not considered a new species unless the changed populations become reproductively isolated from each other or from the unchanged parent populations.
Genetic diversity is beneficial to a species, allowing it to evolve to changing environments. The ultimate source of such variation is mutation—that may be why "mutator" genes (see above) are not completely eliminated from populations and mutation rates may have evolved to optimum values that are not zero. Also, one should remember that new mutations are the main source of variation in microorganisms such as bacteria, which are haploid forms, without a reservoir of recessive genes subject to sexual recombination—although there are several kinds of nonsexual recombination mechanisms (Mayr, 1963, p. 181).
Ambrose, E. J. 1982. The Nature and Origin of the Biological World. N. Y. Halsted Press.
Avers, C. J. 1989. Process and Pattern in Evolution. Oxford University Press.
Ayala, F. J. 1983. Microevolution and macroevolution. In: Bendall, D. S. (Editor). Evolution from Molecules to Men. Cambridge University Press. pp. 387-402.
Berrill, N. J. 1955. The Origin of Vertebrates. Oxford University Press.
Bishop, J. A. and L. M. Cook. 1975. Moths, Melanism and Clean Air. Scientific American 232(1): 90-99. (January)
Bliss, R. B. 1976. Origins Two Models Evolution Creation. Creation-Life Pub. San Diego.
Britten, R. J. 1986. Rates of DNA Sequence Evolution Differ Between Taxonomic Groups. Science 231: 1393-1398.
Bumpus, H. C. 1899. The elimination of the unfit as illustrated by the introduced sparrow, Passer domesticus. Biological Lectures delivered at the Marine Biological Laboratory of Wood's Hole 1898: 209-226.
Calhoun, J. B. 1947. The role of temperature and natural selection in relation to the variations in the size of the English sparrow in the United States. American Naturalist 81: 203-228.
Carson, H. L. 1989. Genetic Imbalance, Realigned Selection, and the Origin of Species. In: Giddings, L. V., K. Y. Kaneshiro and W. W. Anderson (Editors). Genetics, Speciation and the Founder Principle. Oxford University Press. pp. 345-362.
Clarke, P. H. 1974. The evolution of enzymes for the utilization of novel substrates. In: M. J. Carlile and J. J. Skehel (Editors). Evolution in the microbial world. Cambridge University Press. pp. 183-217.
Dagg, A. I. and J. B. Foster. 1976. The Giraffe: its biology, behavior, and ecology. Van Nostrand Reinhold Company.
Darwin, C. R. 1968. The Origin of Species by Means of Natural Selection. (Reprint of the 1859 1st Edition). Penguin Books.
Dawkins, R. 1986. The Blind Watchmaker. W. W. Norton and Company.
Denton, M. 1986. Evolution: A Theory in Crisis. Adler and Adler.
Du Toit, J. T. 1990. Feeding-height stratification among African browsing ruminants. African Journal of Ecology. 28: 55-61.
Dewdney, A. K. 1989a. Computer Recreations. Simulated Evolution: wherein bugs learn to hunt bacteria. Scientific American 260(5): 123-141 (May).
Dewdney, A. K. 1989b. Computer Recreations. Scientific American 261(3): 180-183 (September).
Dobzhansky, T., F. J. Ayala, G. L. Stebbins and J. W. Valentine. 1977. Evolution. W. H. Freeman and Company.
Eakin, R. M. 1968. Evolution of Photoreceptors. Evolutionary Biology 2: 194-242.
Edens, M. 1967. Inadequacies of Neo-Darwinian Evolution as a Scientific Theory. In: Moorhead, P. S. and M. M. Kaplan (Editors). Mathematical Challenges to the Neo-Darwinian Interpretation of Evolution. The Wistar Institute Symposium Monograph Number 5. pp.5-13.
Eldredge, N. 1989. Macroevolutionary Dynamics: Species, Niches and Adaptive Peaks. McGraw-Hill.
Futuyma, D. J. 1986. Evolutionary Biology. 2nd Edition. Sinauer Associates, Inc.
Gould, S. J. 1983. Irrelevance, submission and partnership: the changing role of palaeontology in Darwin's three centennials, and a modest proposal for macroevolution. In: Bendall, D. S. (Editor). Evolution from Molecules to Men. Cambridge University Press. pp. 347-366.
Gould, S. J. 1985. Not necessarily a wing. Natural History 94(10): 12-25. (October).
Grant, P. R. 1972. Centripetal selection and the house sparrow. Systematic Zoology 21(1): 23-30.
Haldane, J. B. S. 1932. The Causes of Evolution. Longmans, Green and Company, Limited.
Haldane, J. B. S. 1936. Primary and Secondary Effects of Natural Selection. Proceedings of the Royal Society of London, Series B. 121: 67-69.
Hall, B. G. 1982. Evolution on a Petri Dish: The Evolved Beta-Galactosidase System as a Model for Studying Acquisitive Evolution in the Laboratory. Evolutionary Biology 15: 85-150.
Halyard, D. 1965. English Sparrows with American Accents. Audubon Magazine May-June: 178-179.
Hardy, G. H. 1908. Mendelian Proportions in a Mixed Population. Science. 28: 49-50. (July 10).
Harris, J. A. 1911. A neglected paper on natural selection in the English sparrow. American Naturalist 45: 314-318.
Hecht, M. K. and A. Hoffman. 1986. Why not neo-Darwinism? A critique of paleobiological challenges. In: Dawkins, R. and M. Ridley (Editors). Oxford Surveys in Evolutionary Biology. Oxford University Press. pp. 1-47.
Jacob, F. 1977. Evolution and Tinkering. Science 196: 1161-1166. (June 10).
Johnston, R. F. 1973. Evolution in the House Sparrow. IV. Replicate studies in phenetic covariation. Systematic Zoology. 22: 219-226.
Johnston, R. F. 1975. Studies in phenetic and genetic covariation. In: Estabrook, G. F. (Editor). Proceeding of the 8th International Conference of Numerical Taxonomy. Freeman. pp. 333-353.
Johnston, R. F. and W. J. Klitz. 1977. Variation and evolution in a granivorous bird: the house sparrow. In: Pinowski, J. and S. C. Kendeigh (Editors). Granivorous Birds in Ecosystems. Cambridge University Press. pp. 15-50.
Johnston, R. F., D. M. Niles and S. A. Rohwer. 1972. Hermon Bumpus and Natural Selection in the House Sparrow Passer domesticus. Evolution 26(1): 20-31.
Johnston, R. F. and R. K. Selander. 1964. House Sparrows: Rapid Evolution of Races in North America. Science 144: 548-550 (1 May).
Johnston, R. F. and R. K. Selander. 1971. Evolution in the house sparrow. II Adaptive differentiation in North American populations. Evolution 25: 1-28.
Keeton, W. T. 1972. Biological Science, 2nd Ed. W. W. Norton and Company, Inc.
Kettlewell, H. B. D. 1959. Darwin's Missing Evidence. Scientific American 200(3): 48-53. (March).
Kettlewell, H. B. D. 1973. The Evolution of Melanism. Clarendon Press.
Lack, D. 1940. Variation in the introduced English sparrow. The Condor 42(5): 239-245.
Lawrence, W. E. and R. E. Rewell. 1948. The cerebral blood supply in the Giraffidae. Proceedings of the Zoological Society of London 118: 202-212.
Levinton, J. S. 1983. Stasis in Progress: The Empirical Basis of Macroevolution. Annual Review of Ecology and Systematics. 14: 103-137.
Lewin, R. 1985. On the Origin of Insect Wings. Science 230: 428-429 (25 October).
Lovtrup, S. 1987. Darwinism: The Refutation of a Myth. Croom Helm.
MacIntyre, R. J. 1982. Regulatory Genes and Adaptation: Past, Present, and Future. Evolutionary Biology 15: 247-286.
Maderson, P. F. A. 1982. The Role of Development in Macroevolutionary Change: Group Report. In: Bonner, J. T. (Editor). Evolution and Development. Springer-Verlag. pp. 279-312.
Marx, J. L. 1988. Evolution's Link to Development Explored. Science 240: 880-882. (13 May)
Mayr, E. 1960. The Emergence of Evolutionary Novelties. In: Tax, S. Evolution After Darwin, volume 1. The Evolution of Life. University of Chicago Press. pp. 349-380.
Mayr, E. 1963. Animal Species and Evolution. The Belknap Press of Harvard University Press.
Maugh, T. H. 1978. Chemical Carcinogens: the scientific basis for regulation. Science 201: 1200-1205. (29 September).
Moore, J. A. 1957 Principles of Zoology. Oxford University Press.
Morris, H. M. (Editor) 1974. Scientific Creationism. Creation-Life Pub. San Diego.
Mortlock, R. P. 1982. Regulatory Mutations and the Development of New Metabolic Pathways by Bacteria. Evolutionary Biology 14: 205-268.
O'Donald, P. 1973. A further analysis of Bumpus' data: the intensity of natural selection. Evolution 27(3): 398-404.
Peterson, I. 1989. Natural Selection for Computers. Science News 136(22): 346-348 (November 25).
Provine, W. B. 1971. The Origins of Theoretical Population Genetics. University of Chicago Press.
Punnett, R. C. 1950. Early Days of Genetics. Heredity 4: 1-10.
Robson, G. C. and O. W. Richards. 1936. The Variation of Animals in Nature. Longmans, Green and Company.
Romer, A. S. 1949. The Vertebrate Body. W. B. Saunders Company.
Salvini-Plawen, L. v. and E. Mayr. 1977. On the Evolution of Photoreceptors and Eyes. Evolutionary Biology 10: 207-264.
Schaeffer, J. P. (Editor). 1953. Morris' Human Anatomy. 11th Edition. The Blakiston Division, McGraw-Hill Book Company, Inc.
Sigurbjornsson, B. 1971. Induced Mutations in Plants. Scientific American. 224(1): 86-95. (January).
Snodgrass, R. E. 1935. Principles of Insect Morphology. McGraw-Hill.
Snodgrass, R. E. 1958. Evolution of Arthropod Mechanisms. Smithsonian Miscellaneous Collections. 138(2): 1-77.
Stanley, S. M. 1979. Macroevolution: Pattern and Process. W. H. Freeman Co.
Summers-Smith, D. 1963. The House Sparrow. Collins.
Taylor, G. R. 1983. The Great Evolution Mystery. Harper and Row.
Vorzimmer, P. J. 1970. Charles Darwin: The Years of Controversy. Temple University Press.
Warren, J. V. 1974. The Physiology of the Giraffe. Scientific American 231(5): 96-105 (November).
(from Frank Sonleitner's critique of Of Pandas and People)
Outline of the Pandas Chapter
The Origin of Species was intended to be an abstract of a larger manuscript that Darwin was working on when he received the celebrated letter from Alfred Russell Wallace. Darwin was rushed into publication of the Origin because of Wallace's independent discovery of natural selection and their joint presentation of a paper at the Linnaean Society in 1858. The first two chapters of the big book were eventually published under the title Variation of Animals and Plants under Domestication. The additional eight and a half chapters were only recently published under the title Natural Selection (Stauffer, 1975). This long version of the Origin included an extensive citation of sources.
The intelligent design (creationist) idea that life is like a manufactured object thoroughly refuted by Hume (see the critique of Excursion Chapter 1: The Origin of Life), Augros and Stanciu (1987, p. 21 fol.) and Arduini (1987).
The main difficulty with a single, unified modern theory of intelligent design is that no such thing exists! Who (or what) are the designer(s) and how do they design? And what did they design? the major groups of organisms? Which then evolved into their constituent species? That requires macroevolution. If latter doesn't exist (as Pandas seems to imply), then was each species created independently (special creation)? An alternate view is proposed by Ambrose (1982, pp. 143, 164) who says the designer took old species, and injected new information to make new ones. This is essentially theistic evolution. Most design proponents (creationists) claim that the designer (creator) works only by supernatural means yet Augros and Stanciu (1987, p. 229) that God made work through natural means. Thus there is potentially disagreement on every aspect of the "theory."
So what about diversity among the design proponents? On one hand, they appear to have uniform views simply because few authors have ever advanced any detailed answers to any of the important questions the "theory" is supposed to address, hence there is not much to disagree upon! When creationists do venture to put forth details (in the pages of the Creation Research Society Quarterly and at various conferences on Creationism), there is virtually no agreement among the various authors. In fact, they tend to ignore each others' ideas! Pandas admits (p. 92) that intelligent design (creationism) embraces both "old earth" and "young earth" proponents. These are two such divergent world views as to render any differences between evolutionists trivial by comparison.
The Question of Kinds: The important question is not what unit of classification was originally designed, but how much can a designed entity change and evolve. This is not at all irrelevant. It determines how much evolution the design proponents (creationists) will admit to! The Pandas authors have something in mind. They admit the evolution and common ancestor for the Hawaiian fruit flies discussed later in the chapter but not for chimps and starfishes (see Pandas, p. 127). What criterion is used to distinguish such cases? Speculation on the subject of the amount of change capable by a created kind runs rampant among creationists—there is no solid ground whatsoever upon which anything can be based! Groups as varied as man (a species), horses (a family), turtles (an order), sharks (a class), sponges (a phylum), algae (a group of phyla), bacteria and fungi (kingdoms) have been listed as examples of kinds (Morris, 1974, p. 87-88). Pandas' statement (p. 78, top of col. 2) that "design proponents accept the idea that species can change within limits. . ." implies that each species represents a kind designed and created de novo.
The limits to change: Pandas' "case" that there are limits to variation is very weak. Bumpus' study on house sparrows (which has questionable validity) only showed stabilizing selection in a population already adapted to a particular environment. The development of considerable geographic variation in the house sparrows introduced into North America illustrated the power of directional selection in creating adaptations to varied environments. Muller only did experiments with ionizing radiation to produce new mutations. No one has tried to produce unlimited change. Animal breeders, for example, have never tried to make their animals into something entirely new; they only wanted to improve or enhance certain useful properties. Yet, domestic dogs presents an enormous assemblage of forms, the extremes differing from each other far more strikingly than many natural species (Lovtrup, 1987, p. 368; Wells, Huxley and Wells, 1931, vol. 1, p. 374 fol.). If they were naturally occurring populations, they would probably be classified into a number of genera! Figure 3.1 illustrates the extent of variation exhibited by domestic dogs. Darwin says the same thing about the domestic races of pigeons (Darwin, 1968, pp. 82-83). Their variation, not only in plumage, but in size, beak shape, shape of the skull and variations in skeleton is such that, if they were wild birds, would be classified as different species, if not different genera. The same holds true for other domestic animals. Some of the more bizarre varieties of goldfish are pictured by Zahl (1973).
The fact that most breeds of domestic animals can and do successfully interbreed and hence are considered the same species is beside the point. What is more important is to realize that they were developed in an artificial reproductive isolation enforced by the breeders. One could imagine selecting for a more "natural" reproductive isolation between two breeds of dogs using the selection protocol applied to Drosophila by Koopman (1950, see below) thus making them true biological species instead of artificially sustained "pseudospecies". With any domestic animals, however, this would entail a prohibitive amount of time, work, money and animals, without any benefit to the breeds.
Even the experiments in artificial selection carried out by Drosophila geneticists had the modest goals of seeing how far a single, particular character (such as number of abdominal bristles) could be modified. When small populations were involved, the new phenotypes were formed entirely by genetic recombination of mutant alleles already existing in the population. Obviously a limit was reached when the genetic variance was exhausted. With larger populations, progressive changes in the character occurred at an irregular rate influenced by the occurrence of new mutations. The limit to change was brought about, not by exhausting the genetic variance, but by pleiotropic effects or by other genes closely linked with those regulating the character being selected causing sterility. This problem could be overcome by relaxing selection and waiting for recombination to unlink the sterility genes before resuming selection. Even so, in experiments selecting for an increase in abdominal bristle number in Drosophila, a fourfold increase—16 times the phenotypic standard deviation in the initial population—was attained. This is comparable in magnitude to many macroevolutionary changes (Futuyma, 1986, pp. 90-91, 207-210; Smith, 1989, pp. 113-117). The development of the most recent "Green Revolution" plant varieties was done with the aid of radiation-induced mutations (Sigurbjornsson, 1971).
It's nice that the "design proponents" agree that research should continue, but they are likely to let evolutionary biologists do the work of demonstrating the feasibility of evolutionary change. After all, who has the incentive to undertake an exhaustive study when he expects negative results? Also, it's too easy to get negative results by just not trying too hard or being persistent enough.
". . . divergence is usually a gradual process. It follows that situations must be expected, and they do occur, in which two groups of populations are too distinct to be regarded as races, but not distinct enough to be considered species. Whether they are named as races or as species is, then, arbitrary and decided solely on grounds of convenience. Biologically, however, these "difficult" situations are highly significant. They are borderline cases of uncompleted speciation, of speciation in the process, of speciation which happens to be unfinished on our time level but which may conceivably be completed in the future… It is no exaggeration to say that if no instances of uncompleted speciation were discovered the whole theory of evolution would be in doubt, we would have to conclude either that evolution did not occur or that the formation of new species is instantaneous. What is a difficulty to the cataloging systematist is a blessing to the evolutionist."
(Dobzhansky, 1958, p. 48; Pandas' footnote 1)
Such borderline cases are quite common, Mayr (1964, p. 165) reports that 94 (or 12.5%) of the 1,367 species and subspecies of native North American birds fall in this category. The species of European house sparrows are an example. These spread west from the Nile valley both north and south of the Mediterranean Sea during an interglacial period. Today the house sparrow and the related Spanish sparrow exist side by side as good species in Spain and the Balkans, yet they interbreed and produce a hybrid zone in Algeria. The Italian sparrow appears to be a stable hybrid of the other two, partially isolated from them by the Alps in the north and the Mediterranean Sea in the south. Yet there is a narrow hybrid zone with the house sparrow in the southern foothills of the Alps and one with the Spanish sparrow in Sicily (Summers-Smith, 1963, chapter 15). A great deal of research has been done on these so-called borderline cases to elucidate the speciation process. It is reviewed by Dobzhansky (1951), Mayr (1963, 1964, 1970) and Stebbins (1950). Shorter accounts are given by Futuyma (1986, chapter 8) and Avers (1989, chapter 8).
Initial spatial isolation of some kind that cuts off gene flow between two populations makes possible evolutionary divergence as the populations adapt to different environments. In general the characters that isolate species are genetically similar to characters that vary within a species. As two populations become more dissimilar genetically, it is less likely that their genotypes will be compatible in a hybrid. Recently it has been suggested that the mismatch repair system might be involved in this process (Rayssiguier et al, 1989; Rennie, 1990). Laboratory experiments have shown incipient reproductive isolation developing between isolated populations of Drosophila and houseflies that have been exposed to divergent artificial selection for responses to various environmental factors (Futuyma, 1986, p. 226).
Natural selection may enhance reproductive isolation when two formerly allopatric populations come into contact and cross-mating produces less fit hybrids. This phenomenon has been produced in the laboratory. Chromosomal abnormalities were introduced into two mutant strains of Drosophila melanogaster to produce two artificial species. After two years in mixed culture where cross-matings were infertile, natural selection produced flies that preferred to mate with their own "kind" (Wallace, 1973). Similar results were obtained by Koopman (1950) who eliminated hybrids in cages with mixed populations of D. pseudoobscura and D. persimilis. (In nature these two species are separated by ecoclimatic preferences but can breed freely in the lab.) When Paterniani (1969) eliminated hybrids between two populations of maize, they developed an isolating mechanism based on different timing of flowering. An analysis of data on 119 pairs of closely related Drosophila species pairs by Coyne and Orr (1989) indicates that these same phenomena occur in nature: both pre- and post-zygotic isolation (see below) increase with time since species divergence and prezygotic isolation evolves more rapidly in sympatric species pairs.
Pandas treatment here is a reasonably accurate but highly simplified account that can be very complex in all its details.
Both are drawn from the left side and to the same scale. One or two points are labelled correspondingly in the two skulls to bring out more clearly how the nose of the fancy breed is shortened.
|Figure 3.1. Illustrations showing the great degree of variability exhibited by the various breeds of the domestic dog (from Wells, Huxley and Wells, 1931, pp. 375, 377).]|
This section says little about the variety of isolating mechanisms specifically mentioning only differences in courtship behavior of Hawaiian fruit flies.
There are a variety of reasons why two species may remain genetically separate. These are usually referred to as isolating mechanisms and may be either premating or postmating (Futuyma, 1986, p. 112):
Premating mechanisms: Potential mates may not meet because they live in different geographic areas separated by a barrier, live in different habitats or have mating seasons at different times. If they do meet, they may not mate because inappropriate courtship rituals. If they do meet and mate, sperm transfer may not take place.
Postmating mechanism: sperm transfer may take place but the egg is not fertilized; or the zygote dies, or the hybrid organism has reduced viability or is partially or completely sterile.
A parallel but slightly different classification is into pre- and post-zygotic mechanisms. Among allopatric species, both pre- and postzygotic isolation evolves in conjunction with increasing genetic divergence while among sympatric species, where a degree of postzygotic isolation exists, prezygotic mechanisms are produced by natural selection (see preceding section on Allopatric Speciation: The Concept Explained).
The Hawaiian fruit flies: These were not discussed in the previous chapter of Pandas. In these flies, allopatric changes in courtship rituals appear to be the main reproductive isolating mechanism. See Carson et al (1970) for an overview of the Hawaiian drosophilids. Kaneshiro and Ohta (1982) and Hapgood (1984) give a popular introduction to these flies. The South American fruit flies mentioned by Pandas (p. 16) are discussed in more detail by Ayala (1978).
The Heliconius butterflies: During dry periods associated with the last Ice Age, the Amazonian rain forest was reduced to isolated "islands" surrounded by savannahs within which the various races of H. erato evolved. When the climate became wetter, the races expanded their range. In some places their range borders occur at natural barriers, such as the Amazon river, strips of grassland along the crest of a range of hills, and the white sand forest in the Guianas. These butterflies has a bad taste and birds quickly learn not to eat them. Their brightly colored wings serve as warning coloration. Interestingly enough, a closely related species, H. melpomene has a similar series of races whose color patterns mimic H. erato. Because both these species are bad tasting, this is as case of Mullerian mimicry where two (or more) species share the same warning color patterns, making it easier for the birds to learn them. The biology of these butterflies and their evolution by neo-Darwinian mechanisms are summarized by Turner (1981); a popular account with colored illustrations of the races is found in Turner (1975); the hybrids of H. melpomene and their genetics are discussed in Turner (1971).
Can reproductive isolation occur without geographic isolation (i.e. can speciation be sympatric?) This is still a controversial question (Futuyma, 1986, p. 228; Mayr, 1963, p. 449 fol.). Rice (1985) succeeded in producing prezygotic reproductive isolation as a result of disruptive selection for habitat in laboratory populations of Drosophila melanogaster.
The Kaibab squirrel: Pandas says that "random mechanisms such as genetic drift and natural selection could possibly operate together to produce reproductive incompatibility." Natural selection is definitely not a random mechanism!! The Kaibab and Albert squirrels differ in the markings on their tails and bellies. Both live in ponderosa pine forests, eating the seeds and branch tips of the tree. They never meet for no ponderosas grow in the desertlike depths of the canyon (Colbert, 1976, p. 308).
Genetic drift, fixation, the founder effect and the bottleneck effect do not result in losses of genes (an entire locus- a part of a chromosome) which is usually very detrimental or fatal. At most only an allele of a gene is lost, or its frequency in the population changed. Each individual in the new species has the same number of genes and amount of information in its DNA as any individual of the old species. Only the variation in this information exhibited by the respective populations has been changed. And this variation can be made up by new mutations. Speciation is not a process involving a loss of information but a change in information.
An observational basis for the introduction of new information resides in the extensive evidence that new genes are formed from mutation in duplicate copies of old genes. This idea is supported by detailed molecular studies on a number of "new" genes (for example, the globin family) that arose in the course of evolution (Avers, 1989, pp. 83-88; Futuyma, 1986, pp. 451-455; Smith, 1989, chapter 11; Ohno, 1970). On the other hand there is no experimental work of any kind that sheds any light on how intelligent designers create new information. In fact, DNA, with all its nonsense sequences, etc. does not look like a product of any intelligence as we know it! Pandas must explain why the DNA of all organisms studied is so full of nonfunctional garbage.
Does speciation fit with the theory that species were originally designed? Apparently that theory can accommodate any observations that might be made. It even includes evolution as a possibility (the Hawaiian Drosophila species evolved)! Is there anything that the theory specifically says must occur or must not occur? Only then can it be tested scientifically. How can one distinguish between information supernaturally added to DNA and that produced by modification of previously existing DNA?
The theory claims to predict that "there may be species on the face of the earth that have undergone no substantial change since their beginning." What are the premises from which that conclusion is derived? It is admitted that species can change. How much is a "substantial" change? When did these species begin, 10,000 years ago or millions of years ago? And if we deal with fossil representatives of a species, we are limited to observing changes in the hard parts and cannot observe their DNA. Clearly this "prediction" cannot be satisfactorily tested. And it doesn't distinguish creation from evolution, because "living fossils" can be explained by stabilizing selection in stable environments.
Design proponents (creationists) have been around longer than evolutionists, yet they have never done any research or even suggested any concrete answers to questions concerning the limits of change, how to identify original species, and what the exact biological definition of species should be. In fact they appear to avoid making any definite statements on these matters.
Footnote 2 is to Darwin (1968, p. 292). There are demonstrable gaps in the fossil record itself. Yet, since Darwin, many examples of unambiguous intermediate forms linking groups have been found. These will be discussed in the critique of Excursion chapter 4 which deals with the fossil record.
Pandas' description of punctuated equilibrium is somewhat misleading. The hypothesis states that most evolution takes place during speciation. The type of changes involved here are those typically distinguishing related species. They are not "major" changes, such as those distinguishing higher categories—genera, families, orders, etc. Such speciation is considered to take place over not 100's of years, but anywhere from 5,000 to 50,000 years (Lewin, 1981) or even 100,000 years (Ayala, 1983, p. 391). The mechanism involved is neo-Darwinian mutation and natural selection occurring in small peripheral populations and is the same as Mayr's peripatric speciation (Mayr, 1963, chapter 17). Extinction "due to factors other than competition" has no more to do with the punctuated equilibrium hypothesis of speciation than any other hypothesis of speciation. The hypothesis predicts gaps between species in the fossil record on the basis that one is unlikely to find fossil strata from the particular positions in space and time that document instances of such a local and fleeting phenomenon. But, in fact, several such examples of such species transitions do exist (Eldredge, 1985, pp. 78, 88). Thus, the hypothesis is not based exclusively on gaps in the fossil record.
The fragmentary quote attributed to Mayr is really from Simpson and the Simpson quote is from Mayr! Pandas is not only confused here but guilty of quoting out of context in order to "prove" their spurious point that "evolutionists still have not solved the fundamental problem of how species originate." More extensive quotes from these two authors are given here:
"It is not so widely recognized that Darwin failed to solve the problem indicated by the title of his work. Although he demonstrated the modification of species in the time dimension, he never seriously attempted a rigorous analysis of the problem of the multiplication of species, of the splitting of one species into two."
(Mayr, 1963, p. 12—Pandas' footnote 3)
"There is another extremely important problem of evolution that has been only implicit up to this point. It was curiously neglected by Darwin, whose book called The Origin of Species is not really on that subject, but the neglect has been richly compensated in more recent years (emphasis added). The problem is how, in fact, do species originate; that is, not only how does one specific lineage evolved and adapt, but also how do multiple specific lineages arise and become divergently adapted."
(Simpson, 1964, p. 81, Pandas' footnote 4)
Mayr's work in particular more than makes up for the deficiency in the Origin. Thus, contrary to Pandas' conclusion, most evolutionists consider that allopatric speciation explains the origin of new species. Even Denton, who considers evolution a theory in crisis, says that speciation has been explained by neo-Darwinism (Denton, 1986, pp. 82-83, 344).
Furthermore, the intelligent design explanation, that species "were intelligently designed by some informative selection of the material for their genotypes" is totally empty of information content. We are given no explanation or understanding how this occurs! How does the designer (or designers) accomplish this? Furthermore, is each species made de novo (special creation), or is new information "injected" into a population that is speciating in an otherwise natural manner as suggested by Ambrose (1982, pp. 143, 164)? This latter suggestion is theistic evolution, a concept anathema to the special creationists (Morris, 1974, pp. 215-220). Evolutionists suggest the new information arises from mutations of existing genes or duplicated copies of those genes. How does one distinguish between such events and the "injection" of new information by a designer (creator)?
As we mentioned earlier, the amount of variation exhibited by domestic breeds is equivalent to that found within genera or even families of naturally occurring organisms. And this is remarkable, considering the short span of time (centuries) and the small population sizes involved. To proceed any farther requires waiting for the appropriate mutations to occur. In this context, remember that many of the advanced Green Revolution plant strains were derived from stocks irradiated to speed up the mutation rate.
The evolutionists' three problems:
Lines stable enough to be called species are probably brought about by stabilizing selection. Pandas is well aware of this process (see Excursion chapter 2). Why do they think this is a problem? Pandas' further statement that the world is filled with distinct and stable species is not entirely true. Speciation is a slow process taking thousands of years. There are many examples of species in the middle of this process which allows us the opportunity to study it. It has been mentioned earlier that 12.5% of the 1,367 species and subspecies of North American birds are only partially distinct and have known intermediate forms, indicating only partial isolation. This is the context of the quote from Dobzhansky (1958) on p. 79 of Pandas! Also Pandas apparently accepts the formation of the Hawaiian fruit fly species by evolutionary means (Pandas, p. 82). And instances of fossil intermediates between species have been found (Eldredge, 1985, pp. 78 fol., 88).
The second problem of long-term stability is also basically explained by stabilizing selection although the examples of it are exaggerated. For example there is not just one "shark". There are many species and genera. Some of the living genera go back to the Cretaceous. Even then, we can only say that the teeth and those parts of the cartilaginous skeleton that normally calcify secondarily and would form fossils, haven't changed very much. The quote from Thorpe (Pandas footnote 5) comes from Taylor (1983, pp. 141-142).
As for the third problem, we have been mentioned that there is abundant evidence that new information (new genes) arise through mutation of duplicated copies of old genes. Again, it must be pointed out that the intelligent design "explanation"—that a "designer did it" is empty of any information content and provides no understanding of the phenomena at all.
Again, the two types of evolution ‘microevolution' and ‘macroevolution' (see Pandas, p. 61) grade into one another without any clear borderline. Some evolutionists (Rensch, 1960, p. 1; Futuyma, 1986, p. 397) consider micro-evolution to include those processes that occur within a species or lead to a new species while macro-evolution are those processes leading to new genera, families, etc. According to this view, Pandas chapters 2 and 3 really deal with microevolution! Macroevolution is usually studied through the fossil record. The neo-Darwinian position is that larger macroevolutionary differences arise through the successive accumulation of microevolutionary changes that occur within a species or during speciation (Futuyma, 1986, p. 397). Bock (1970) studied the adaptive radiation of the Hawaiian honeycreepers, specifically the macroevolutionary changes in the bill and feeding habits of the four genera of the subfamily Psittirostrinae and showed that these changes occurred by a series of steps involving micro-evolutionary modifications on the species level. See Futuyma (1986, pp. 32-33), Ralph (1982) and Lewin (1982, pp. 58-60) for an introduction to these birds. They are also mentioned briefly at the beginning of Pandas' Overview section 3. The magnitude of their morphological diversity is such that, if they were not connected by intermediate species, it would be enough to place them in different families or orders (Stebbins, 1982, pp. 68, 134). A comprehensive discussion of macroevolution and related topics is found in Levinton (1988).
Ambrose, E. J. 1982. The Nature and Origin of the Biological World. Ellis Horwood Ltd.
Arduini, F. J. 1987. Design, Created Kinds and Engineering. Creation/Evolution 7(1): 19-23 (Spring).
Augros, R. and G. Stanciu. 1987. The New Biology: Discovering the Wisdom in Nature. New Science Library of Shambala Publications Inc.
Avers, C. J. 1989. Process and Pattern in Evolution. Oxford University Press.
Ayala, F. J. 1978. The Mechanisms of Evolution. Scientific American 239(3): 14-27 (September).
Ayala, F. J. 1983 Microevolution and macroevolution. In: Bendall, D. S. (Editor). Evolution from Molecules to Men. Cambridge University Press. pp. 387-402.
Bock, W. J. 1970. Microevolutionary sequences as a fundamental concept in macroevolutionary models. Evolution 24: 704-722.
Carson, H. L., D. E. Hardy, H. T. Spieth, and W. S. Stone. 1970. The Evolutionary Biology of the Hawaiian Drosophilidae. In: Hecht, M. K. and W. C. Steere (Editors). Essays in Evolution and Genetics in Honor of Theodosius Dobzhansky. Appleton-Century-Crofts. pp. 437-544.
Colbert, E. H. (Editor). 1976. Our Continent: A Natural History of North America. National Geographic Society.
Coyne, J. A. and H. A. Orr. 1989. Patterns of speciation in Drosophila. Evolution 43(2): 362-381.
Darwin, C. R. 1968. The Origin of Species. Reprint of the 1st (1859) Edition. Penguin Books.
Dobzhansky, T. 1951. Genetics and the origin of species. Columbia University Press.
Dobzhansky, T. 1958. Species after Darwin. In: Barnett, S. A. (Editor) A Century of Darwin. William Heinemann. pp. 19-55.
Eldredge, N. 1985. Time Frames. Simon and Schuster. N. Y.
Futuyma, D. J. 1986. Evolutionary Biology. 2nd Edition. Sinauer Associates, Inc.
Hapgood, F. 1984. Fruit Fly Fandango. Science 84 5(7): 68-74. (September).
Kaneshiro, K. and A. T. Ohta. 1982. The Flies Fan Out. Natural History 91(12): 54-59 (December).
Koopman, K. F. 1950. Natural selection for reproductive isolation between Drosophila pseudoobscura and Drosophila persimilis. Evolution 4: 135-148.
Levinton, J. 1988. Genetics, Palaeontology and Macroevolution. Cambridge University Press.
Lewin, R. 1981. Evolutionary Theory Under Fire. Science 210: 883-886. (21 November).
Lewin, R. 1982. Thread of Life. Smithsonian Books.
Lovtrup, S. 1987 Darwinism: The Refutation of a Myth. Croom Helm.
Mayr, E. 1963. Animal Species and Evolution. The Belknap Press of Harvard University Press.
Mayr, E. 1964. Systematics and the Origin of Species from the viewpoint of a zoologist. (reprint of a 1942 book). Dover Publications.
Mayr, E. 1970. Populations, Species, and Evolution: An Abridgment of Animal Species and Evolution. The Belknap Press of Harvard University Press.
Morris, H. M. (Editor). 1974. Scientific Creationism. Creation-Life Publishers.
Ohno, S. 1970. Evolution by Gene Duplication. Springer-Verlag.
Paterniani, E. 1969. Selection for reproductive isolation between two populations of maize, Zea mays. Evolution 23: 534-5447.
Ralph, C. J. 1982. Birds of the Forest. Natural History 91(12): 40-45 (December).
Rayssiguier, C., D. S. Thaler and M. Radman. 1989. The barrier to recombination between Escherichia coli and Salmonella typhimurium is disrupted in mismatch-repair mutants. Nature 342: 396-401 (23 November).
Rennie, J. 1990. Kissing Cousins: A DNA repair system stops species for interbreeding. Scientific American 262(2): 22-23 (February).
Rensch, B. 1960. Evolution Above the Species Level. Columbia University Press.
Rice, W. R. 1985. Disruptive selection on habitat preference and the evolution of reproductive isolation: an exploratory experiment. Evolution 39: 645-656.
Sigurbjornsson, B. 1971. Induced mutations in plants. Scientific American 224(1): 86-95. (January).
Simpson, G. G. 1964. This View of Life. The World of an Evolutionist. Harcourt, Brace and World.
Smith, J. M. 1989. Evolutionary Genetics. Oxford University Press.
Stauffer, R. C. 1975. Charles Darwin's Natural Selection: Being the second part of his big species book written from 1856 to 1858. Cambridge University Press.
Stebbins, G. L. 1950. Variation and Evolution in Plants. Columbia University Press.
Stebbins, G. L. 1982. Darwin to DNA, Molecules to Humanity. W. H. Freeman and Company.
Summers-Smith, D. 1963. The House Sparrow. Collins.
Taylor, G. R. 1983. The Great Evolution Mystery. Harper and Row.
Turner, J. R. G. 1971. Two thousand generation of hybridisation in a Heliconius butterfly. Evolution 25: 471-482.
Turner, J. R. G. 1975. A Tale of Two Butterflies. Natural History 84(2): 29-36.
Turner, J. R. G. 1981. Adaptation and evolution in Heliconius: A Defense of NeoDarwinism. Annual Review of Ecology and Systematics 12: 99-121.
Wallace, B. 1973. Man's Humanity. Saturday Review of the Sciences. February: 48-49.
Wells, H. G., J. S. Huxley and G. P. Wells. 1931. The Science of Life. Doubleday, Doran and Co.
Zahl, P. A. 1973. Those Outlandish Goldfish. National Geographic 143(4): 514-533 (April).
(from Frank Sonleitner's critique of Of Pandas and People)
Outline of the Pandas Chapter
This chapter tries to convince us that there is no fossil evidence for evolution; that there are gaps and no transition forms; that all forms appear "fully developed and functional"; that evolution is untestable because it is a theory about unique past events.
The text quoted from Dobzhansky (1957) on p. 91 (Footnote 1) continues in the original as follows:
"The applicability of the experimental method to the study of such unique historical processes is severely restricted before all else by the time intervals involved, which far exceed the lifetime of any human experimenter. And yet, it is just such impossibility that is demanded by antievolutionists when they ask for "proofs" of evolution which they would magnanimously accept as satisfactory. This is about as reasonable a demand as it would be to ask an astronomer to recreate the planetary system, or to ask an historian to reenact the history of the world from Caesar to Eisenhower."
Pandas concludes that theories of origins can't be tested empirically, yet on the very next page admits that they can be tested by looking for convincing similarity between present and past causes and by considering circumstantial evidence. Now all scientific theories are explanations postulating mechanisms involving entities that cannot be directly observed (ex: atoms, electrons, subatomic particles, electromagnetic waves, curved space, etc.). They are all tested against circumstantial evidence. One deduces what observable consequences a theory would have, then looks for them under appropriate circumstances. The procedure is the same whether one is investigating ephemeral, short-term repeatable phenomena or long-term unique phenomena. The philosopher of science, Karl Popper, considers evolution a fact and Darwinism (i.e. the mechanism of natural selection) a scientific theory and the methods of the historical sciences perfectly compatible with those of science in general (Sonleitner, 1986). For an example of testing an evolutionary hypothesis, see the supplement on Science.
The fossil record is a highly biased record of past life. The vast majority of organisms die and are eaten or decay and leave no trace of their former existence, the material of their bodies being recycled in the ecosystem. Organisms that produce hard mineral skeletons and live in shallow marine environments are the most likely to leave traces in the fossil record. Terrestrial organisms living on flood plains near water are most likely to be buried in river or lake deposits. Yet such continental deposits, being of limited extent and in locations at higher altitudes on the earth's surface are much more likely to be eroded away in subsequent eras. Deep sea sediments are destroyed by subduction of ocean plates and rarely, if ever, incorporated into land surfaces to appear as sedimentary outcrops.
Only about 8 to 10 of the animal phyla (normally producing large populations of individuals with hard skeletons or shells in the shallow water marine habitat) have extensive fossil records and are actually found in the Cambrian period. Highly unusual deposits, such as the Burgess Shale, only emphasize, through their preservation of unique soft-bodied forms, how strongly biased is the "normal" fossil record. Because soft parts can be preserved only under very special circumstances, there are only about a dozen or so extensive deposits of soft-bodied creatures (Gould, 1983). Many phyla of soft-bodied forms have no fossil record at all; some are found only in such special deposits as the Burgess Shale.
Although fossil species appear to persist unchanged through many strata, sequences of species clearly showing evolutionary trends abound, and records of one species transforming into another also exist (see below) although such are rare. And, of course fossil species are fully formed and functional! A partially formed and nonfunctional organism would die before or shortly after birth. Such species couldn't possibly exist to form fossils. Actually the phrase "fully formed" is used by Gould (1977) to describe the first appearance of a species in the fossil record. Gould simply meant that usually such species have all the features that characterize them throughout their subsequent period of stasis. He did not mean that higher categories (genera, families, orders, etc) appear fully formed in this sense (they don't) nor did he mean that transitional forms are not fully formed in the sense that they are incomplete and nonfunctional.
It's important to note that design proponents are divided on the issue of the earth's age. In truth, virtually all of them claim that the earth is young, identifying them as the well-known creationists. But the fact that intelligent design can embrace two such radically different interpretations of the earth's geology is proof that "intelligent design" is empty of any specific explanatory content. The intelligent designer/God is supernatural working by supernatural means! Pandas admits this on p. 100.
Contrary to the assertions of Pandas, we do find transitional forms between many major groups; these are documented in any volume on vertebrate or invertebrate paleontology. Pandas claim that many phyla should emerge high in the branches of a phylogenetic tree has no basis in evolutionary theory and is just creationist wishful thinking. This idea is found in Augros and Stanciu (1987, p. 169) and Taylor (1983, p. 69). It should seem obvious that the main branches (phyla) of the evolutionary tree should occur at its base, just as is the case with actual trees. On the other hand, smaller categories such as Classes and Orders (ex: the Mammals) have arisen comparatively recently. Today many of the gaps between major groups have been filled; intermediate forms between species are rare, but do exist as will be seen below in the section on Gaps In The Fossil Record. The quote from Darwin (footnote 2) is from Darwin, 1968, p. 292.
Pandas' varying claims that 95% of the phyla (overview chapter 4) or all phyla but Platyhelminthes and some Burgess Shale forms (excursion chapter 4) appear at the beginning of the Cambrian Period is incorrect. In particular Pandas' Figure 4-2, purporting to show the fossil record of the known phyla, is false. (Why are not the lines in the figure labeled?) According to Valentine (1987), who provides a fully labeled figure of his own for the animal phyla—reproduced here as Figure 4.3, only 7 (possibly 8) of the phyla are found at the beginning of the Cambrian, 3 more appear in the mid-Cambrian, 2 in the Ordovician, 4 more in the Devonian, 3 more in the Carboniferous, 1 in the mid-Tertiary, and 6 (including Platyhelminthes) have no fossil record at all. Depending on whose classification is followed the number of phyla without a fossil record would vary from 6 to 19. (The bizarre forms from the Burgess shale are not included in Valentine's figure and the 3 Carboniferous appearances are of soft-bodied forms from Illinois. Three of the Cambrian phyla (Cnidaria, Arthropoda and Annelida) possibly occur in the Precambrian. Of all the phyla only the Cnidaria, Porifera, Mollusca, Brachiopoda, Arthropoda, Echinodermata, and Bryozoa are abundant in the fossil record. The others are found only sporadically. Thus the lines in Pandas Figure 4-2, continuous from the Cambrian to the present, indicating appearance in all fossil strata are incorrect and misleading.
Of the non-animal phyla, the prokaryote Cyanophyta and bacteria are found in the Precambrian. The Rhodophyta or red algae (mid-Cambrian), Chlorophyta or green algae (late Cambrian) and Eumycota or fungi (Devonian) may have appeared in the Precambrian. The Pyrrophyta or dinoflagellates appeared in the late Ordovician; the Phaeophyta or brown algae possibly appear in the Devonian; the Chrysophyta or diatoms and golden-brown algae appear in the late Jurassic; the Bryophyta in lower Carboniferous and the Tracheophyta in the Silurian but mainly in the Devonian and Carboniferous. Three algal phyla, The Xanthophyta or yellow-green algae, the Euglenophyta and the Myxomycota or slime molds have no fossil record at all (Stewart, 1983).
All of the phyla may have appeared early in the earth's history, but the fossil record documents possibly 5 in the Precambrian (not counting many of the strange soft-bodied forms in the Ediacara fauna) and 13 at some time in the Cambrian (not counting the strange forms in the Burgess shale.)
The Cambrian "explosion" was preceded by the soft-bodied fauna of the Precambrian Ediacara fauna and many trace fossils: burrows and tracks of soft-bodied forms for several hundred millions of years back into the Precambrian (Stanley, 1976). Fossils of eukaryote cells go back 1 billion years and Prokaryote bacterial and blue-green algal communities go back 3.5 billion years (Kaveski and Margulis, 1983). The Cambrian "Explosion" itself coincided with an extensive marine transgression flooding the continental shelves following a late Precambrian glaciation that enormously increased living space in the shallow marine life zone (Clarkson, 1986, p. 48). This may have triggered a great adaptive radiation of animal forms, which, along with the acquisition of hard skeletons and shells, produced the rich fossil faunas of the Cambrian. Hard skeletons may have arisen under the pressure of predator-prey interactions. Traces of incipient skeletonization are found with some Ediacara forms (Kaveski and Margulis, 1983). Once all the major niches were filled by this first radiation of phyla, there was possibly no ecological "room" for the subsequent evolution of any new phyla, only the further development and specialization of classes, etc., among the already existing phyla. Thus the Cambrian adaptive radiation was similar to that of the mammalian orders after the extinction of the dinosaurs and other reptilian forms at the end of the Mesozoic left open many ecological niches. Stanley (1976) reviews the Precambrian and Cambrian fossil record in detail and concludes (p. 72):
"If the foregoing assessment is generally correct, we can abandon the traditional view that the origins of major fossil taxa near the start of the Cambrian were so sudden and simultaneous as to represent a major enigma."
The Valentine quote (Pandas footnote 3) is from Valentine and Erwin, 1987, p. 84.
Lack of transitional forms between the phyla is probably due to the soft-bodied nature of those forms in the 50 to 100 million years preceding the Cambrian which precluded fossilization. Again, contrary to the assertions of Pandas, we do have unambiguous transitional series linking Hyracotherium to the modern horse, the reptiles to the mammals, remarkable transitional forms between fishes and amphibians, and between reptiles and birds, and other miscellaneous transitional series in a hundred or more forms (Simpson, 1953, p. 224). Paleontologists such as Raup, Gould and Stanley do not deny these statements, their quotes on Pandas, p. 96. are taken out of context; their correct meaning will be explained below.
Depositional and erosional gaps are very common and well-documented in the geological record (Carroll, 1988, pp. 570 fol.; Smith, 1988, Eldredge, 1987, p. 12 fol.). Many of our gaps in the fossil record result from the absence of sedimentary deposits of certain ages. Thus, for example, Romer (1968, p. 230 fol.) mentions the lack of Ordovician continental sediments, the dearth of freshwater sediments in the Silurian, the paucity of continental deposits of Mississippian, early Jurassic and early Cretaceous ages. It also must be remembered that although a sedimentary formation may have a large areal extent, the only parts accessible to palaeontologists are the places where surface outcrops occur. This is especially true for vertebrates. (Invertebrate fossils can be recovered from well cores and are used to identify the sedimentary layers below the surface.)
That real gaps occur in the record of fossils is shown by the gaps existing in the temporal ranges of higher taxa as determined by first and last occurrence. Examples are given by Smith (1988, p. 144) and Simpson (1953, p. 371). Paul (1982) concludes that the fossil records of echinoderms and vertebrates are at least 25% and 40% incomplete at familial and generic levels, respectively. The fact the latest fossil coelacanths come from the Cretaceous, yet there is a living coelacanth, Latimeria, shows how great such gaps can be.
One must be careful in interpreting quotations about gaps and transitional forms. When a transitional forms is found, it doesn't eliminate a gap but divides a large one into two smaller ones. Thus, as the fossil record becomes more complete the number of gaps actually increases although their average size decreases. Also, there is more than one level of transitional form. Figure 4.1 presents a hypothetical phylogenetic tree. A descendent species (B) may be linked to an ancestor (A) through a chain of species and speciations. Fossils of each of the species are transitional forms illustrating the evolutionary trend from ancestor to descendent (dark dots in fig. 4.1). In addition there are the transitional forms between each of the species (open dots in fig. 4.1). It is the transition forms between species that are rare. These are the ones being referred to by Raup (1979, footnote 4), Gould (1977, footnotes 5, 6) and Stanley (1979, footnote 7) in the quotations given on p. 96 of Pandas. Although they may be rare, they are not completely nonexistent! Eldredge (1985, pp. 78 fol., 88) found two instances of transitional sequences between species of phacopid trilobites that he was studying. Williamson (1981) reported several cases of transitional forms between species in Cenozoic African fossil molluscan faunas. These instances corroborate the punctuated equilibrium model. Pandas' assertion (on p. 98) that punctuated equilibrium rests entirely on the absence of data is incorrect. The explanation for the "punctuated" changes is simply allopatric speciation by natural selection in small peripheral populations (Eldredge, 1985, pp. 85, 118). This is not a fanciful alternative to neo-Darwinism, but a mechanism discussed in detail by Mayr (1963) who considered it a part of modern neo-Darwinism (Mayr, 1967; Sonleitner, 1987). Dawkins (1986, pp. 250-251) considers punctuated equilibrium a minor modification of neo-Darwinism. The most common misconception of "punctuated equilibria", one that is always cited by creationists, is that it is a saltationist model of overnight change based on sudden large-scale mutations (Eldredge, 1985, p. 141, Sonleitner, 1987).
Gingerich (1983) documents several cases of intermediate transitional forms linking species of mammals which follow a more gradualistic pattern. Carroll (1988) discusses three more examples of well-documented progressive changes within species and genera and lists references to seven others. Chaline (1987) gives several examples of gradual change in the rodent fossil record. Both Carroll (1988) and Smith (1988) conclude, on the basis of many studies of evolutionary rates, that evolution is neither exclusively gradual nor punctuational but irregular or opportunistic, sometimes exhibiting gradual and sometimes punctuational patterns. Thus the fossil record does provide instances of direct fossil evidence for evolutionary change between species. For a comprehensive review of transitional forms in the fossil record, see Cuffy (1984).
Transitional species are much more common and acknowledged by all palaeontologists. Eldredge (1982) mentions two between the cheirurid and phacopid trilobites. On the right-hand side of fig. 4.1, the fossils produced by the hypothetical phylogenetic tree are used to document a phylogenetic sequence between the ancestral form (A) and the descendent form (B). Note that only one of them (the circled one) is on the direct line of descent. In practice it is almost impossible to demonstrate that a particular fossil was on the direct line of descent between two forms or on a side branch, even though it represents a transitional stage. This is the problem that Patterson is referring to in the quotes given on p. 106 (footnote 10 from Patterson in Sunderland, 1981, p. 21 or 1988, p. 89.) and on p. 113 of Pandas (footnote 16 from Patterson, 1978, p. 133). Thus, if this diagram were to represent the evolution of birds from theropod dinosaurs, Archaeopteryx might be the circled dot or one of the others.
It is interesting that Eldredge and Gould consider that punctuated equilibrium is the face value interpretation of the fossil record! Considering the bias of the fossil record to organisms with robust skeletons and shells, and the lack of sedimentary deposits of any number of ages, especially terrestrial, continental ones, one cannot assume, as Pandas does (p. 98) that the known fossil record is reasonably complete. Actually Pandas is assuming that it is complete without qualification. The claim that the pattern of phylogenetic origins is illustrated by Pandas' Figure 4-4 may be true only if the bars represent species. Yet groups of species present undeniable evolutionary trends (see Figure 4.1; Eldredge, 1985, pp. 129, 222; Stanley, 1979, pp. 190, 194, 247; Stanley, 1986, p. 163). Pandas' further claim that new knowledge is only extending species ranges into older and older strata is false. New finds may be of older species that represent transition forms closer to the ancestral form of the group. One only has to compare the vertebrate paleontology works of Romer (1945), Romer (1966) and Carroll (1988) to see all the new forms—genera, families, orders—that have been discovered in the past 50 years! Examples are Petrolacosaurus, the earliest and most primitive diapsid reptile (Reisz, 1977), the whales with regressed hind legs (see below), and the conodont animal (Aldridge and Briggs, 1989).
It should be noted that Pandas' table of "living fossils" exaggerates the situation. The animals mentioned represent genera (aardvarks, alligators, sturgeons, horseshoe crabs, galatheid crabs, echinoneid sea urchins), families (New World Porcupines, Snapping turtles, Sirens, Bowfin fishes) and orders (Notostracan crustaceans). There is a Precambrian fossil that superficially looks like Kakabekia (Galston, 1978).
Evolutionists object to the view of intelligent design (creationism) because it doesn't provide an explanation, only a supernatural mystery. Pandas devotes two chapters (i.e. 2 and 3) to evolutionary mechanisms. Where are the chapters devoted to intelligent design mechanisms? There are none. How does(do) the intelligent designer(s) create organisms? What are their methods and limitations? None are given because the proponents of intelligent design (creationists) have none. They all assert that the designer (creator) is supernatural and uses supernatural means. It one doesn't know how the designer(s) work and what their goals are, one cannot deduce the nature of what they would produce. Why are creations periodically wiped out? Why are they reintroduced? (as in the case of Latimeria after the Cretaceous extinction of the coelacanths). Without specific answers to these questions, we cannot know whether the intelligent design hypothesis fits the fossil data or not. Certainly the fossil record is not as Pandas describes it. The first fishes are agnaths without jaws, bony internal skeletons and some without paired fins; the earliest bird, Archaeopteryx didn't have a beak but toothed jaws and its wing was more of a feathered arm, etc.
Pandas' claim that the fossil record does not show a progressive development of mammalian characters is utterly false. The quoted "authority" (Lewin, 1981, footnote 9 on p. 100) is Roger Lewin, reporter for Science, apparently creating a snappy sentence to close his one-page report in 1981. This is the same year that the second of two papers by Kermack, Mussett and Rigney on Morganucodon, the animal exactly straddling the fence between reptiles and mammals, was published. In contrast, J. A. Hopson, professor of anatomy and evolutionary biology at the University of Chicago says that the reptile to mammal transition is "considered by palaeontologists to be the best-documented example in the fossil record of an evolutionary sequence connecting two major structural grades." (Hopson, 1987). Carroll (1988, p. 360) states "The sequence from the early amniotes to the early mammals is the most fully documented of the major transitions in vertebrate evolution." Eldredge (1987, p. 151) says " it's one of the very finest examples of anatomical evolution yet found in the fossil record."
The reptilian subclass Synapsida includes two orders, The Pelycosauria, known from the Pennsylvanian to the Upper Permian and the Therapsida, from the middle Permian into the Mid-Jurassic. The Pelycosaurs retain many of the features of early reptiles. Most of the skeletal features common to mammals appeared over time in the therapsids, whose latest members can hardly be distinguished from the Mesozoic mammals.
"Late mammal-like reptiles and earliest mammals now known intergrade so perfectly that anatomical definition depends arbitrarily on a single point: the nature of the articulation of mandible and skull. Even that is not clear-cut, because opinion differs as to whether "reptiles" became "mammals" when they acquired a dentary squamosal articulation (Kermack and Mussett, 1958) or when the articular-quadrate articulation (not known ever to have been lost) ceased to function as suspensorium (Crompton, 1958)"—Simpson (1960, p. 169).
For more details about this well-documented transition, see the supplement: The Reptile-Mammal Transition.
Throughout the Mesozoic, the mammals remained small shrew-like animals, represented in the fossil record mainly by fragments of teeth, jaws and skulls and few post-cranial bones (Stahl, 1974, p. 400). It was not until the demise of the dinosaurs, that the numerous orders of Tertiary mammals appeared. Pandas' oversimplified diagram (Figure 4-7) conceals a number of important points about the origin of these orders.
The origin of these orders occurred in the late Cretaceous and Palaeocene. This was an age of extensive uplift and erosion and terrestrial deposits are rare, being found only in Montana, Wyoming and Alberta. Although a large quantity of fossils have been found, most of these are fragments and many of the animals are known only from isolated teeth. Identifying incipient branches from the mammalian stem is rendered even more difficult because these forms had not diverged far enough to clearly show the traits characteristic of the later Cenozoic orders. Although some of these mammals are referred to as primitive primates, ungulates and carnivores, they were "all small clawed animals that scampered after insects and perhaps supplemented their diet with soft-boded invertebrates and some plant food." (Stahl, 1974, p. 421-423). The mammalian orders are not strikingly isolated in the fossil record. Some ancestral forms from the late Cretaceous and Paleocene are known (see Carroll, 1988, chapters 19, 20).
The system of hierarchic taxonomic groups, which works well with living organisms, is ill-suited for the inclusion of fossil forms which document a branching phylogenetic tree. There are two ways to divide a phylogenetic tree into discrete groups, the horizontal and vertical classifications. In a horizontal classification, the ancestral forms near the stem of the tree are put into a separate group from their descendants, while a vertical classification extends the descendent groups as far down the tree as they can be traced by fossils (see Figure 4.2). Vertical classifications tend to be preferred by evolutionists, although they separate into different categories primitive forms that actually may be very similar. (Stahl, 1974, p. 423; Simpson, 1945, p. 18). The early and mid-Paleocene mammals were quite similar; if we knew no placentals after the middle Paleocene and thus had no reason for separating and classifying them vertically with their descendants, they would all be placed within one order (Simpson, 1953, p. 342). Carroll (1988, p. 505, 578) and Stanley (1979, p. 65) also discusses these classification practices and their application to the origin of the mammalian orders.
The mammalian fossil record refutes the Pandas' statement that fossil types are fully formed when they first appear. The therapsids acquired mammalian osteological characters gradually over millions of years. The early Tertiary mammals fossils are very much alike. Hyracotherium, the ancestor of the horse and linked to modern horses by a complete transitional sequence, and Homogalax, the ancestor of the tapirs, (representing two suborders of the Order Perissodactyla) are almost identical in structure and require a skilled palaeontologist to distinguish them (Simpson, 1960, pp. 122-123). Similarly the earliest chalicotheroid Paleomoropus (representing another perissodactyl suborder) differs from the above two forms only by slight differences in the teeth (Radinsky, 1969). The difference between Hyracotherium and its ancestors in the earlier heterogeneous ungulate order Condylarthra, involves slight specializations in the teeth and jaws for chewing plant material and in the ankle for running (Radinsky, 1966). The first artiodactyl was, except for its tarsal joint, a typical member of the Condylarthra (Mayr, 1963, p. 596). The earliest carnivores (the creodonts) also have many characters in common with the condylarths. One genus of the Condylarthra, Protogonodon contains, on balance of resemblance in small details, some species that could be classified as carnivores and others as ungulates. All the early Paleocene carnivores and ungulates together are less varied than species occurring in some single living family among the recent carnivores (Simpson, 1953, p. 345). Higher taxa (in this case mammalian orders) start out as ordinary speciations and only after much diversification of the descendants of those species are they recognized as such (Carroll, 1988, p. 578; Simpson, 1953, p. 342).
Of the 32 orders of mammals, 14 are entirely extinct, and the extant orders contain many extinct forms. Of the 257 families, 139 or 54% are extinct; of the 2864 genera, 1932 or 67% are extinct. Table 4.1 shows the percentage of families extinct in each epoch and the geological age of the 932 extant genera documents a progressive changes in the mammalian fauna to those of the present day. Thus Pandas' Figure 4-7 is incomplete and in error; there were no advanced carnivores and ungulates in the Eocene. Also the solid vertical bars hide the changes that occurred within each group and the great similarity of the early forms of all the orders. See Figures 4.5 and 4.6 for more accurate diagrams of the mammalian fossil record. Figure 4.6 in particular, shows some of the more recently found ancestral forms of the mammalian orders.
Although the origin of whales is represented by a fossil gap, there are evolutionary trends in the known fossils. The earliest genera, known only from cranial material, have skulls closely resembling terrestrial mammals of the early Cenozoic, especially the mesonychids. They also retained a primitive tooth count with distinct incisors, canines, premolars, and multirooted teeth, which are modified or lost in later whales. The skull of the oldest known whale, Pakicetus, (Gingerich, 1983; Carroll, 1988) from the early Eocene of Pakistan is intermediate between those of the late Eocene whales and mesonychids; the auditory bullae are only partially modified for hearing in water. The remains (which do not include any post-cranial elements) were found in sediments deposited at a river mouth together with remnants of terrestrial mammals. Pakicetus may have been amphibious, spending time both on land and in the water.
The earliest whales also retain a vestigial pelvic girdle joined to the vertebral column which is lost in later whales (Stahl, 1974, p. 488; Carroll, 1988, p. 523, Landau, 1983). Quite recently, new specimens of a middle Eocene whale Basilosaurus have been found that possess tiny but functional three-toed hind limbs (Gingerich et al, 1990). The loss of the hind limbs in later whales has been accomplished apparently by suppressing the action of a hind limb developmental system still retained by modern whales. Hind limb rudiments are present in the embryo and there are a number of observations at whaling stations of whales exhibiting hind limbs with various degrees of development (Conrad, 1983). Why should an intelligently designed whale have a developmental system to produce functional hind limbs which is normally not activated?
The ancient whales from the Eocene (Archaeoceti) were toothed predators. From the features of their skulls, it is inferred that they lacked the echolocation mechanisms of modern toothed whales (Odontoceti) and the filter feeding structures of the modern baleen whales (Mysticeti). The late Oligocene Mammalodon from Australia is a toothed mysticete structurally intermediate between the mysticetes and the archaeocetes. The extinct cetotheres are intermediate between Mammalodon and the living mysticetes (Fordyce, 1984). The extinct family Agorophiidae is temporally and morphologically intermediate between archaeocetes and more advanced odontocetes (Carroll, 1988, p. 525).
The later Eocene whales still have paired nostrils near the front of the skull. Subsequent fossils form a sequence with the nostrils migrating farther and farther back onto the top of the head. This was accomplished without changing their position relative to the skull bones—the maxillary and premaxillary bones being "dragged" backwards over the more posterior elements (Romer, 1945, p. 486 fol.; Colbert, 1980, p. 328-329).
Although bats are the second largest mammalian order (after the rodents) they have by far the poorest fossil record. Having delicate skeletons and living mainly in the tropics is not conductive to fossil preservation. Also, the early insectivores are known only from teeth and skull fragments Without post-cranial skeletal material, such fossils cannot be identified as being bat ancestors (Romer, 1968, p. 181; Simpson, 1945, p. 180). For example, the Paleocene Zanycteris and Picrodus may have been ancestral bats instead of insectivores (Simpson, 1945, p. 180); Adapisoriculus (a tree shrew?) and Leptacon may also have been bats or semi-bats (Hall, 1984). The earliest identifiable bat, Icaronycteris from an Early Eocene lake bed deposit has a fully developed wing that is primitive in some aspects (Hall, 1984; Jepsen, 1970).
The fossil record of the horse most convincingly shows that organisms have really evolved. It is a record with possibly only one gap where the record is not complete (Simpson, 1961, p. 224; Simpson, et al, 1957, p. 787; Gould, 1987; Patterson, 1978, p. 131). Other good examples of species lineages are found in the condylarths, other perissodactyls, artiodactyls, taenidonts (Patterson, 1949), titanotheres (Gregory, 1951, vol. 2, p. 825), oreodonts (Stokes, 1973, p. 144), elephants (Aguirre, 1969; Colbert, 1980, p. 430) and carnivores (Dunbar and Waage, 1969, p. 464; Colbert, 1980, p. 341).
Transition forms between Crossopterygian fishes and Labyrinthodont amphibians are represented by the late Devonian fossils Ichthyostega, Elpistostege, and Hesperoherpeton. According to Simpson (1953):
"In these creatures we really do have an essentially continuous transition between two very high categories: classes. The Greenland forms are so completely and amazingly intermediate as to be animals that could not possibly exist if higher categories arose as such and by saltation."
Schmalhausen (1968) says:
"The ichthyostegids were actually transitional forms between the crossopterygian fishes and the Amphibia."
Because of all the fishlike features that they retained, the ichthyostegids were described by the paleontologist Jarvik as four-footed fishes. The bones of the skull, palate and lower jaw are very similar to those of the fish Eusthenopteron except in their proportions—the face is longer in the ichthyostegids. The most distinctive feature of the crossopterygian organization is the division of the skull into two parts, movably articulated with each other. Traces of this division are found in the ichthyostegids, confirming their derivation from the crossopterygians! (Schmalhausen, 1968, pp. 35, 58; Stahl, 1974, chapter 6). In addition, ichthyostegids have other similarities to crossopterygians: labyrinthine type teeth; rudiments of gill covers; a lateral line system of the head is enclosed in bony canals and not in open grooves as in later amphibians; similar vertebral column; a genuine fishlike tail, a laterally compressed body and dermis with fishlike scales. In other respects they are similar to early labyrinthodont amphibians. The lobe fins of the crossopterygian fishes already had all the bony elements of tetrapod limbs, lacking only the distal organization into definite phalanges. Recent discoveries in Greenland reveal that Ichthyostega and the related genus Acanthostega had flipper-like limbs with more than 5 digits (Coates and Clack, 1990; Gould, 1991). Acanthostega apparently had a stapes that controlled palatal and spiracular ventilation movements as is found in lungfishes (Clack, 1990). For more details about this transition, see the supplement: The Fish-Amphibian Transition.
A skeletal pattern appropriate to the ancestors of the amphibians is found in middle Devonian crossopterygians, giving at least 20 million years available for the evolution of the amphibian represented by Ichthyostega (Carroll, 1988, p. 166). The Pandas' statement that the air bladder of the fish had to be transformed into the lungs of the amphibian is incorrect. Lungs evolved first in the earliest freshwater fishes to allow breathing in oxygen-poor ponds by gulping air. Only later when the bony fishes invaded the marine environment did the lung become an air bladder. (Romer, 1949, pp. 331- 333; Gould, 1989)
The differences between amphibians and reptiles lies mainly in their soft parts which are not fossilized. The earliest reptiles from the mid-Carboniferous strata are very similar in their osteology to labyrinthodont amphibians, to the extent that the two groups are hard to distinguish. The order Seymouriamorpha, including the genus Seymouria, which structurally occupies an almost exactly intermediate position between advanced amphibians and primitive reptiles, and once classified as reptiles are now considered to be amphibians. The same is true of the genus Diadectes of the reptile order Diadectomorpha. (Romer, 1968; Stahl, 1974). This prompted Mayr (1963, p. 597) to write, "The amphibians grade so insensibly into the reptiles that the assignment of certain fossils becomes rather arbitrary". Carroll (1988, chapter X) gives an up-to-date and extensive account of the earliest reptiles.
"Modern amniotes are linked to their Paleozoic ancestors by a relatively complete sequence of intermediate forms." (Carroll, 1988, p. 193.)
Although Pandas asserts that "nearly every organism possesses equally and in full measure the defining characteristics of its taxon" (p. 104) this is definitely not true of Archaeopteryx. In fact, Pandas admits that it's some odd-ball kind of "intermediate" form (p. 23, 106). The skeleton of Archaeopteryx is virtually identical to that of a small dinosaur. If has none of the skeletal specializations of birds (even some theropods had fused clavicles (=furculas) (Carroll, 1988, p. 340; Paul, 1988, p. 107; Wellnhofer, 1990, p. 72). The forelimb shows no specialized features and is identical to that in forms such as Compsognathus. Archaeopteryx has no sternum and hence no keel. It did have abdominal ribs like Compsognathus. Thus the teeth and long bony tail are only two of a complete suite of reptilian characters possessed by Archaeopteryx. If it weren't for the preservation of the feather impressions, it would have been identified as a dinosaur (Carroll, 1988, p. 339). In fact that happened to several specimens that had poor or no accompanying feather impressions (Wellnhofer, 1990). Obviously it was not necessary to bridge a large gap in bony structure to transform a dinosaur into a "bird". If birds had become extinct at the end of the Jurassic period, Archaeopteryx would be considered an aberrant and specialized dinosaur and not the ancestor of a new vertebrate class. An extensive discussion of Archaeopteryx, other Mesozoic birds and their relations to the bird-like theropod dinosaurs is given by Paul (1988). See also the supplement: The Reptile-Bird Transition.
Lacking a sternum, small pectoral muscles must have been exclusively attached to the furcula. Without a sternum and hence no keel, and also no triosseal canal, the supercoracoideus muscle probably had the same function as in other tetrapods, not being specialized to lift the wings as in modern birds and pterosaurs. The wings were raised by back muscles such as the deltoideus major (Feduccia, 1980, p. 58; Carroll, 1988, p. 342). It also lacked openings in its bones for air sacs. Thus it probably didn't have bird-like lungs (although Paul (1988, p. 104) discusses evidence of the theropod's rib cage that suggests the presence of abdominal air sacs.) The largest wing feathers originate on the ulna, yet the ulna is smooth, in contrast to modern birds where the ulna has small knobs where the feathers are anchored firmly to the bone by ligaments. Thus it would seem that the main feathers of Archaeopteryx were not anchored to the skeleton. All these features suggest that Archaeopteryx was probably a weak flier (Wellnhofer, 1990).
Creationists make much of the fact that the hoatzin of South American has claws. Actually these are found only in the nestlings which use them to climb about the nest and adjacent branches. They are lost in the adult, whose forelimb elements are reduced and fused as in typical modern birds (Feduccia, 1980, p. 45). Actually many modern birds possess one or more wing claws. These are always more fully developed in the embryo and chick and become vestigial or lost in the adults (Fisher, 1940).
Skin, scales and feathers are rarely fossilized so the lack of fossil sequences of transitional feather-forms is understandable. Most birds have reptilian scales on their legs while some, such as the Pheasant and Black Grouse, have feathers on their legs. In the course of development these feathers grow from the leg scales. The early development of the feathers on the other parts of the body is identical to that of scales. Down feathers are just highly branched scales (Heilmann, 1927, p. 129 fol.). Some early Triassic archosaurs, such as Longisquamata had elongate, keeled, overlapping scales which may have aided in thermoregulation as they appear to do in certain modern lizards. Those of Ornithosuchus even had grooves or rays extending from the central rib or keel, suggesting the precursors of feathers (Bakker, 1975; Feduccia, 1980, p. 54; McLoughlin, 1979, p. 32 fol.). Figure 4.4 shows an example of an intermediate scale-feather found in late Jurassic lake deposits of Kazakhstan that has long, thin flat barbs but no barbules (Rautian, 1978).
Other paleontologists suggest that feathers may have evolved directly for flight. If a common squirrel falls or is shaken from a branch, it spreads its limbs, assuming the attitude of a flying squirrel, which allows it, like a human sky diver, to partially control its fall, to swerve at an angle of as much as 60 degrees and land relatively lightly. Thus the slightest fringe of elongated scale or proto-feather along the trailing edge of the forelimb would have an immediate advantage in parachuting or jumping (Feduccia, 1980, p. 57). A similar advantage would accrue from the slightest development of a patagium (i.e. a skin membrane connecting front and hind legs), leading to the flying squirrels, galago, flying phalangers, pterosaurs and bats.
Although all modern birds have horny beaks instead of toothed jaws, tooth buds appear temporarily in the bird embryo. In fact, birds have a complete set of genic instructions for making fully formed reptilian teeth (Kollar and Fisher, 1980; Gould, 1980) which normally are never used!
All the references cited here (Carroll, 1988; Feduccia, 1980; Heilmann, 1927) including all the prominent proponents of punctuated equilibrium (Eldredge, 1987, p. 187; Gould, 1986; Patterson, 1978, p. 133; Stanley, 1981, p. 176; Stanley, 1986, p. 461) consider Archaeopteryx a transition form.
According to Stanley (1981, p. 174):
"Creationists commonly cite outdated lamentations of botanists and paleobotanists that the fossil record of plants fails to support evolution. The simple truth here is that much of the plant fossil record is terribly incomplete. Also, there has never been more than a handful of people in the world studying fossil leaves, and in the early days serious errors were made in taxonomic assignments. The result was a confused picture of ancient plant life. As I have noted, the biggest problem, the sudden rise of the flowering plants—Darwin's "abominable mystery"—has been resolved by new fossil evidence. We now have fossils documenting a pattern of early adaptive radiation (in the early Cretaceous, see p. 90) Here we have a prime example of how the concept of evolution has been strengthened rather than weakened since the time of Darwin."
The Pandas' quotation from Corner (1961: see Pandas, p. 107, footnote 11) is that author's way of bemoaning the lack of fossil evidence for flowering plants ("...and it is well known that the fossil record tell nothing about the evolution of flowering plants" -Corner, 1961, p. 100). Corner advocates a return to classification and natural history because much plant evolution has been obscured by bad classification—he treats the genus Ficus at length. He also laments the continuing destruction of the tropical rain forest "...with its immense store of plants, saturated with the effects of evolution." Finally, lest the reader still think that Corner is a creationist, the sentence immediately preceding the Pandas' quotation states: "The theory of evolution is not merely the theory of the origin of species, but the only explanation of the fact that organisms can be classified into this hierarchy of natural affinity."
Again the simplified diagram in Pandas (Figure 4-12) is designed to hide the evolutionary patterns that actually exist. An analogous diagram (Chart 28.1) from a paleobotany book (Stewart, 1983) summarizing the distribution of the major plant groups in geological time shows groups succeeding each other as would be expected on the basis of evolution. Stewart (1983, chapter 27) also discussed at length the fossil evidence for the origin and evolution of the angiosperms. At various other points in his book, Stewart describes the known transition fossils between other divisions of the plant kingdom. Thus the Pandas' quotations from Bold (1967) on p. 96 (footnote 8) and Corner are out of date.
The quotation from Stanley (1979, p. 39) given on p. 108 of Pandas (footnote 12) is a statement about the gradualistic model and not a statement saying there are no transition forms. Thus consider the following quote from Stanley (1981, p. 174):
"A frequent claim of creationists is that the fossil record contradicts that concept of evolution. One argument here is that there are no transitional forms between distinctive groups of animals or plants. This is not true . . . Archaeopteryx represents a single intermediate form. Elsewhere, despite the punctuational nature of many transitions, we have available series of forms that more fully represent steps in the origins of certain major groups ... in 1966 H. K. Erben announced his discovery that a group of specimens from the Devonian of Germany could be assembled into a graded series showing several stages in the evolution from bactritid nautiloids to ammonoids."
Careful consideration of human anatomy reveals that man was originally "designed" as a four-legged animal and many of the changes related to bipedality are imperfect (Krogman, 1951). Darwin (1871: Pandas, p. 198, footnote 13) did not cite any fossil evidence in his book The Descent of Man because none had yet been found. Pandas claims that still no intermediate fossil forms are found. This is not true. The fossil record "is a steady stream of intermediates." (Eldredge, 1982, p. 128). Also there are many more than just a few dozen specimens as claimed in the quotation from Science 84. This comes from an article written by a science reporter (Rensberger, 1984, Pandas' footnote 14) doing a story on photographs of the "most complete original specimens available" that were later to be exhibited at the American Museum of Natural History later in 1984. As of the late 1970's, it took a three volume 817 page Catalogue of Fossil Hominids (Oakley et al, 1977), to list and describe all the known hominid fossils. M. H. Wolpoff studied the skulls, jaws and teeth of 92 H. erectus specimens alone (Walpoff, 1984). A convenient reference to all this material is Tattersall et al, 1988.
Pandas' Figure 4-13 contains a number of gross inaccuracies that have been pointed out by Scott (1990). Old World monkeys are not older than apes, chimpanzees are pongids, and the fossil forms Pliopithecus, Australopithecus and Oreopithecus have not continued to the present! Gibbons are left out. There are no fossils of chimp, orang and gorilla and none of the fossil records are continuous, as the diagram implies.
Pandas' Figure 4-14 is supposed to show an evolutionary sequence favored by many evolutionists. But it shows 10 hypothetical intermediate forms between A. afarensis and H. habilis, 5 more between habilis and erectus and 5 more between erectus and sapiens. Actual specimens called "archaic sapients" exist; they are not hypothetical. Because of their anatomical closeness and overlapping characteristics, most anthropologists would say that these last three species form a lineage without any further intermediates. For example, the oldest specimens of H. erectus have skull volumes of about 800 cc. Over the next million years the cranial capacity expanded to about 1200 cc. while the jaw and tooth sizes shrunk. The youngest specimens grade into modern man through presapiens (archaic sapiens) forms (Jelinek, 1980, Tattersall et al, 1988, p. 49 fol.).
Again Scott (1990) commented on the illustration of A. africanus in Pandas' Figure 4-15 "as drawn with a chimp thorax, a human pelvis and a cranium from a K-Mart Halloween display. It looks like a tracing from a physical anthropology text, with much lost in translation." Comparison of these figures with similar ones from Johanson and Edey (1981, pp. 182-183) (see Figure 4.7) show that the skull and thorax of A. africanus are portrayed by the Pandas' figure in a grossly inaccurate way and there are minor inaccuracies in the pelvic bones of both A. africanus and H. sapiens. In general, Pandas gives very little information about the hominid specimens. For example, nothing is mentioned about Australopithecine bipedality or the changes in their dentition. All that is mentioned about H. erectus is the brow ridges and sloping forehead. That specimens from all over the world spanning a million years of time should all have been suffering from Vitamin D deficiency is ludicrous.
The sentence on p. 112: "Was Homo habilis really the earliest human being, or was it only a primate like the australopithecines?" is nonsensical. All monkeys, apes and men are primates—as is mentioned on p. 109! Contrary to Pandas, H. habilis had an average brain size of 800 cc.—almost twice as big as a chimp's but with a similar body size (Leakey, 1981, p. 131) and hands similar to the Australopithecines showing very human-like opposable thumb (Johanson and Edey, 1981, p. 321) and finger tips but with still some traces of climbing features (Sussmann and Stern, 1982). The quote from Pilbeam (1984) on p. 113 (footnote 15) simply refers to minor changes in the dating and branching pattern in the phylogenetic tree leading up to hominids and not that Pilbeam has become a creationist! The meaning of the Colin Patterson quote on the same page (footnote 16) has been explained above in the section on GAPS IN THE FOSSIL RECORD. The fossil record really presents irrefutable direct evidence for macroevolution (Halstead, 1984).
Aguirre, E. 1969. Evolutionary History of the Elephant. Science 164: 1366-1376 (20 June).
Aldridge, R. J. and D. E. G. Briggs. 1989. A Soft Body of Evidence. Natural History (May): 6-11.
Augros, R. and G. Stanciu. 1987. The New Biology. New Science Library.
Bakker, R. T. 1975. Dinosaur Renaissance. Scientific American 232(4): 58-70. (April)
Bold, H. C. 1967. Morphology of Plants, 2nd Ed. Harper & Row, N. Y.
Carroll, R. L. 1988. Vertebrate Paleontology and Evolution. W. H. Freeman and Co. N. Y.
Chaline, J. 1987. Arvicolid Data (Arvicolidae, Rodentia) and Evolutionary Concepts. Evolutionary Biology 21: 237-310.
Clack, J. A. 1990. Discovery of the earliest-known tetrapod stapes. Nature 342: 425-427. (23 November).
Clarkson, E. N. K. 1986. Invertebrate Palaeontology and Evolution. 2nd Ed. Allen and Unwin, Boston.
Coates, M. I. and J. A. Clack. 1990. Polydactyly in the earliest known tetrapod limbs. Nature 347: 66-69. (6 September)
Colbert, E. H. 1980. Evolution of the Vertebrates. 3rd Ed. Wiley.
Conrad, E. C. 1983. True Vestigial Structures in Whales and Dolphins. Creation/Evolution X: 8-13
Corner, E. J. H. 1961. Evolution. In: MacLeod, A. M. and L. S. Cobley (editors). Contemporary Botanical Thought. Quadrangle Books. Chicago. pp. 95-114.
Cuffy, R. J. 1984. Paleontologic evidence and organic evolution. In: Montagu, A. (Editor). Science and Creationism. Oxford University Press. pp. 255-281.
Darwin, C. R. 1968. The Origin of the Species. Penguin Classics edition. London: Penguin Books.
Darwin, C. R. 1871. The Descent of Man. New York. Modern Library.
Dawkins, R. 1986. The Blind Watchmaker. W. W. Norton and Co. N. Y.
Dobzhansky, T. 1957. On Methods of Evolutionary Biology and Anthropology. Part I. Biology. American Scientist. 45: 381-392.
Dunbar, C. O. and K. M. Waage. 1969. Historical Geology, 3rd Ed. Wiley. N. Y.
Eldredge, N. 1982. The Monkey Business: A Scientist Looks an Creationism. Washington Square Press, N. Y.
Eldredge, N. 1985. Time Frames. Simon and Schuster. N. Y.
Eldredge, N. 1987. Life Pulse: Episodes from the Story of the Fossil Record. Facts On File Pub. N. Y.
Feduccia, A. 1980. The Age of Birds. Harvard University Press.
Fisher, H. I. 1940. The Occurrence of Vestigial Claws on the Wings of Birds. American Midland Naturalist. 23: 234-243.
Fordyce, E. 1984. Evolution and zoogeography of cetaceans in Australia. In: Archer, M. and G. Clayton (editors). Vertebrate Zoogeography and Evolution in Australasia. Hesperian Press. pp. 929-948.
Galston, A. W., 1978. A Living Fossil. Natural History 87(2): 42-44. (February).
Gingerich, P. D. 1983. Evidence for evolution from the vertebrate fossil record. Journal of Geological Education 31: 140-144.
Gingerich, P. D., B. H. Smith and E. L. Simons. 1990. Hind Limbs of Eocene Basilosaurus: Evidence of Feet in Whales. Science 249: 154-157 (13 July).
Gould, S. J. 1977. Evolution's Erratic Pace. Natural History 86(5): 12-16.
Gould, S. J. 1980. Hen's Teeth and Horse's Toes. Natural History 89(7): 24-28 (July).
Gould, S. J. 1983. Nature's Great Era of Experiments. Natural History (July): 12-21.
Gould, S. J. 1986. The Archaeopteryx Flap. Natural History (September): 16-25.
Gould, S. J. 1987. Life's Little Joke. Natural History (April): 16-25.
Gould, S. J. 1989. Full of Hot Air. Natural History (October): 28-38.
Gould, S. J. 1991. Eight (or Fewer) Little Piggies. Natural History (January): 22-29.
Gregory, W. K. 1951. Evolution Emerging (2 vols.) Macmillan Co. N. Y.
Hall, L. 1984. And then there were bats. In: Archer, M. and G. Clayton (editors). Vertebrate Zoogeography and Evolution in Australasia. Hesperian Press. pp. 837-852.
Halstead, L. B. 1984. Evolution—The Fossils Say Yes! In: Montagu, A. (Editor). Science and Creationism. Oxford University Press. pp. 240-254.
Heilmann, G. 1927. The Origin of Birds. Dover Pub., Inc. reprint (1972)
Hopson, J. A. 1987. The Mammal-like Reptiles: A study of transitional fossils. The American Biology Teacher. 49(1): 16-26. (January).
Jelinek, J. 1980. European Homo erectus and the Origin of Homo sapiens. In: Konigsson, L-K. Current Argument on Early Man. Pergamon Press, pp. 137-144.
Jepsen, G. L. 1970. Bat Origins and Evolution. In: Wimsatt, W. A. (editor). Biology of Bats, volume 1. Academic Press. pp. 1-64.
Johanson, D. C. and M. Edey. 1981. Lucy: The Beginnings of Humankind. Simon and Schuster, N. Y.
Kaveski, S. and L. Margulis. 1983. The "Sudden Explosion" of Animal Fossils About 600 Million Years Ago: Why? The American Biology Teacher. 45(2): 76-82.
Kollar, E. J. and C. Fisher. 1980. Tooth Induction in Chick Epithelium: Expression of Quiescent Genes for Enamel Synthesis. Science 207: 993-995 (29 February).
Krogman, W. M. 1951. The scars of human evolution. Scientific American 185(6): 54-57.
Landau, M. 1983. Whales: Can Evolution Account for Them? Creation/Evolution X: 14-19.
Leakey, R. E. 1981. The Making of Mankind. E. P. Dutton, N. Y.
Lewin, R. 1981. Bones of Mammals' Ancestors Fleshed Out. Science 212: 1492 (26 June).
Mayr, E. 1963. Animal Species and Evolution. The Belknap Press of Harvard University Press
Mayr, E. 1967. Evolutionary Challenges to the Mathematical Interpretation of Evolution. In: P. Moorehead and M. M. Kaplan (Editors.) Mathematical Challenges to the Neo-Darwinian Interpretation of Evolution. Philadelphia: Wistar Institute Press, pp. 47-58.
McLoughlin, J. C. 1979. The Archosauria. Viking Press. N. Y.
Oakley, P., B. G. Campbell and T. I. Molleson. Catalogue of Fossil Hominids. (3 vols.) Part I: Africa (2nd Ed. 1977, 223 pp.), Part II: Europe (1971, 379 pp.); Part III: Americas, Asia, Australasia (1975, 215 pp.) British Museum of Natural History.
Patterson, B. 1949. Rates of Evolution in Taeniodonts, in: Jepsen, G. L., E. Mayr and G. G. Simpson (editors). Genetics, Paleontology, and Evolution. Princeton University Press. N. J.
Patterson, C. 1978. Evolution. Cornell University Press, Ithaca, N. Y.
Paul, C. R. C. 1982. The Adequacy of the Fossil Record. In: Joysey, K. A. and A. E. Friday (Editors). Problems of Phylogenetic Reconstruction. Academic Press. pp. 75-117.
Paul, G. S. 1988. Predatory Dinosaurs of the World. Simon and Schuster, N. Y.
Pilbeam, D. 1984. The Descent of Hominoids and Hominids. Scientific American 250(3): 84-96.
Radinsky, L. B. 1966. The adaptive radiation of the phenacodontid condylarths and the origin of the Perissodactyla. Evolution 20: 408-417.
Radinsky, L. B. 1969. The early evolution of the Perrisodactyla. Evolution 23: 308-328.
Raup, D. 1979. Conflicts Between Darwin and Paleontology. Field Museum of Natural History Bulletin. 30(1)
Rautian, A. S. 1978. A unique bird feather from Jurassic lake deposits in the Karatau. Paleontologicheskii Zhurnal 12: 106-14. (English translation by Scripta Pub. Co and American Geological Institute: Paleontological Journal 12(4):520-528).
Reisz, R. R. 1977. Petrolacosaurus, the Oldest Known Diapsid Reptile. Science 196: 1091-1093. (3 June).
Rensberger, B. 1984. Bones of our Ancestors. Science 84. 5(3): 29-39.
Romer, A. S. 1945. Vertebrate Palaeontology. 2nd Ed. University of Chicago Press.
Romer, A. S. 1949. The Vertebrate Body. W. B. Saunders Co. Philadelphia.
Romer, A. S. 1966. Vertebrate Palaeontology. 3rd Edition. University of Chicago Press
Romer, A. S. 1968. Notes and Comments on Vertebrate Palaeontology. University of Chicago Press.
Schmalhausen, I. I. 1968. The Origins of Terrestrial Vertebrates. Academic Press. N. Y. and London.
Scott, E. C. 1990. Of Pandas and People. NCSE Reports 10(1): 16-18
Simpson, G. G. 1945. The Principles of Classification and a Classification of Mammals. Bulletin of the American Museum of Natural History. 85.
Simpson, G. G. 1953. The Major Features of Evolution. Columbia University Press, N. Y.
Simpson, G. G. 1960. The History of Life. In: Tax, S. (Editor). Evolution After Darwin. Volume 1. The Evolution of Life. University of Chicago Press. pp. 117-180.
Simpson, G. G. 1961. Horses. The Natural History Library, Anchor Books, Doubleday & Co., Inc. N. Y.
Simpson, G. G., C. S. Pittendrigh and L. H. Tiffany. 1957. Life. An Introduction to Biology. Harcourt, Brace & Co., Inc. N. Y.
Smith, G. S. 1988. Gaps in the Rock and Fossil Records and Implications for the Rate and Mode of Evolution. Journal of Geological Education. 36: 143-146.
Sonleitner, F. J. 1986. What Did Karl Popper Really Say About Evolution? Creation/Evolution 6(2): 9-14
Sonleitner, F. J. 1987. The Origin of Species by Punctuated Equilibria. Creation/Evolution 7(1): 25-30.
Stahl, B. J. 1974. Vertebrate History: Problems in Evolution. McGraw-Hill. N. Y.
Stanley, S. M. 1976. Fossil data and the Precambrian-Cambrian evolutionary transition. American Journal of Science 276: 56-76.
Stanley, S. M. 1979. Macroevolution: Pattern and Process. W. H. Freeman and Co. San Francisco.
Stanley, S. M. 1981. The New Evolutionary Timetable: Fossils, Genes, and the Origin of Species. Basic Books, Inc. N. Y.
Stanley, S. M. 1986. Earth and Life Through Time. W. H. Freeman and Co. N.Y.
Stewart, W. N. 1983. Paleobotany and the evolution of plants. Cambridge University Press. London.
Stokes, W. L. 1973. Essentials of Earth History, 3rd Ed. Prentice-Hall, N. J.
Sunderland, L. 1981, 1988. Darwin's Enigma: The Fossil Record. Master Book Pub., Santee, Calif.
Sussmann, R. L. and J. T. Stern. 1982. Functional morphology of Homo habilis. Science 217: 931-934. (3 Sept.)
Tattersall, I., E. Delson and J. Van Couvering (Editors). 1988. Encyclopaedia of Human Evolution and Prehistory. Garland Publishing.
Taylor, G. R. 1983. The Great Evolution Mystery. Harper and Row.
Valentine, J. W. 1987. Invertebrate Organization: A Review. In: Boardman, R. S., A. H. Cheetham and A. J. Rowell (Editors). Fossil Invertebrates. Blackwell Scientific Publications. pp. 4-18.
Valentine, J. W. and D. H. Erwin. 1987. Interpreting Great Developmental Experiments: The Fossil Record. In: R. A. Raff and E. C. Raff (Editors). Development as an Evolutionary Process. A. R. Liss, N. Y. pp. 71-107.
Wellnhofer, P. 1990. Archaeopteryx. Scientific American 262(5): 70-77 (May)
Williamson, P. G. 1981. Palaeontological documentation of speciation in Cenozoic molluscs from Turkana Basin. Nature. 293: 437-443.
Walpoff, M. H. 1984. Evolution in Homo erectus the question of stasis. Paleobiology 10(4): 389-406.
(from Frank Sonleitner's critique of Of Pandas and People)
Outline of the Pandas Chapter
This chapter tries to discredit all the morphological evidence for evolution. It tries to convince us that homology is a uniquely evolutionary concept based on evolution and totally subjective so that evolutionary classifications and relationships are based on circular reasoning.
Louis Agassiz, (1807-1873) the well-known 19th century creationist zoology/geologist wrote in his 1857 Essay on Classification (Davenport, 1983; pp. 45, 46, 104):
"Nothing is more striking throughout the animal and vegetable kingdoms than the unity of plan in the structure of the most diversified types."...
"During the first decade of this century, naturalists began to study relations among animals which had escaped almost entirely the attention of earlier observers. Though Aristotle knew already that the scales of fishes correspond to the feathers of birds, it is but recently that anatomists have discovered the close correspondence which exists between all the parts of all animals belonging to the same type, however different they may appear at first sight. Not only is the wing of the bird identical in its structure with the arm of man, or the fore leg of a quadruped, it agrees quite as closely with the fin of the whale, or the pectoral fin of the fish, and all these together correspond in the same manner with their hind extremities. Quite as striking a coincidence is observed between the solid skull-box, the immovable bones of the face and the lower jaw of man and the other mammals, and the structure of the bony frame of the head of birds, turtles, lizards, snakes, frogs and fishes. But this correspondence is not limited to the skeleton; every other system of organs exhibits in these animals the same relations, the same identity in plan and structure, whatever be the difference in the form of the parts, in their number, and even in their functions. Such an agreement in the structure of animals is called their homology, and is more or less close in proportion as the animals in which it is traced are more or less nearly related."
"Embryology has, however, a wider scope than to trace the growth of individual animals, . . . it ought also to embrace a comparison of these forms and the successive steps of these changes between all the types of the animal kingdom, in order to furnish definite standards of their relative standing, of their affinities, of the correspondence of their organs in all their parts."
The discovery of these underlying similarities was used by the 19th century morphologists to bring order into the living universe and gave rise to the idealistic morphology of the German Naturphilosophen. J. W. Goethe (1749-1832), the German poet and intellectual who also did vertebrate dissections asserted that ". . . are all formed according to an Urbild (Archetype) which varies only more or less in its basically constant parts . .." (Mayr, 1982). The renowned French morphologist Cuvier (1769-1832) recognized four great archetypes: vertebrates, articulates (annelids and arthropods), molluscs and radiata (the remaining invertebrates). The English anatomist, Richard Owen (1804-1892) who worked on the Archetype and homologies of the vertebrate skeleton, (Mayr, 1982; Gould, 1986b) distinguished between analogies (similar of function) and homologies:
"Analogue: a part or organ in one animal which has the same function as another part or organ in a different animal."
"Homologue: the same organ in different animals under every variety of form and function."
Homologies were identified by means of the principle of connections of Geoffroy Sainte-Hilaire (1772-1844). When in doubt of the homology of structures in widely different organisms, say a fish and a mammal, "the sole general principle one can apply is given by the position, the relations, and the dependencies of the parts . . ." (Mayr, 1982).
Richard Owen was the last serious representative of morphologists looking for the real essence, the ideal type (Urform); unity of plan; and a limited number of archetypes. This however, was a radical departure from orthodox natural theology, where each structure designed purely for the sake of utility for a particular species. "But then why should the anterior extremity of a mole (digging tool), a bat (wing), a horse (running leg) and a whale (paddle) have essentially the same structure, while the wings of insects, birds and bats, all serving the same function, have very different structures?" The Archetype principle was a deistic mode of ascribing structure to natural laws; it had primarily esthetic satisfaction, being devoid of explanatory capacity. In fact, the idealistic morphologists were completely as a loss to explain the unity of plan and, more particularly, why structures rigidly retained their pattern of connections no matter how the structures were modified by functional needs (Mayr, 1982).
"Nothing can be more hopeless than to attempt to explain this similarity of pattern in members of the same class, by utility or by the doctrine of final causes. The hopelessness of the attempt had been expressly admitted by Owen in his most interesting work on the ‘Nature of Limbs.' On the ordinary view of the independent creation of each being, we can only say that so it is; — that it has so pleased the Creator to construct each animal and plant." (Darwin, 1968, p. 414).
Only on the assumption of descent with modification did the complex combination of unity of plan and adaptive variety fall into place! Natural selection can only select modifications that are functional and of adaptive value to an organism. It follows that any "new" organ or structure must be derived by modification of some already existing organ or structure either though an intensification or shift in its function (Mayr, 1963, p. 602 fol.).
Although homology has now been redefined: "Attributes of two organisms are homologous when they are derived from an equivalent character of the common ancestor." (Mayr, 1982), the determination of homologies follows from Geoffroy's principle of connections, embryology, fossil sequences and more recently from biochemical and genetic similarities (Gould, 1988). The more detailed the similarities between two structures the less likely that they are the result of parallel or convergent evolution and the more likely that they are derived from a common ancestor. Thus, homologies are determined and evaluated by evolutionary biologists employing exactly the same criteria as used by the 19th century pre-evolutionary anatomists. Simpson (1961) devotes an entire chapter to Taxonomic Evidence and Evolutionary Interpretation, including the criteria for homology.
Homologies of all the anatomical parts of vertebrates, including bones, teeth, muscles, nerves, heart and blood vessels and internal organs are pretty definitely settled, most of the work having been done by pre-evolutionary biologists. A summary of this information is given by Goodrich (1958). Some of the problems, such as the pandas and various bird orders (ex: flamingoes, Gould, 1985) involve homologies of the adaptive modifications of these parts. Modern techniques, such as DNA-DNA hybridization, promise to solve these problems, as was recently done with the birds. Australian birds show a picture similar to the marsupials and placentals, with many ecological equivalents to birds in other parts of the world. The DNA-DNA hybridization technique indicates that these are cases of parallel evolution, as are the marsupials.
Pandas' implication that evolutionists recognize different homologies than did the pre-evolutionary biologists is false. All the 19th century biologists considered human hands and dogs' paws homologous. Owen, in fact, tried to homologize the skeletal elements of all vertebrates in terms of one Archetype (Gould, 1986b). Pandas' assertion that no continuously evolving series of fossils have ever been found is false. This has been discussed with regard to Excursion chapter 4. Pandas' point that some evolutionists are skeptical about the value of fossils in determining phylogenies is misleading, to say the least. Footnote 1 refers to Patterson (1981) and Forey (1982). Patterson concludes that the belief that fossils are the only or best means of determining evolutionary relationships is a myth because he has not found any instances of fossils overturning theories of relationship based on recent organisms (Patterson, 1981, p. 218). Patterson is a cladist and cladists prefer to construct classifications using data on the morphology, physiology, embryology, biochemistry, etc. of living forms. Forey (1982) distinguishes between the philosophies behind cladograms versus phylogenetic trees, using brachiopods (the great majority of which are known only as fossils!) as an example.
Structures may look different and function differently, but still be considered homologous, not to "satisfy" evolutionary theory, but because their morphological interconnections (Geoffroy's principle of connections), embryological similarities, etc. warrant that conclusion (see above). Structures having a similar appearance and function in unrelated groups are analogous. Furthermore, they usually differ in their morphological details, as do, for example, the skeletal structure of the wings of bats, birds and pterosaurs.
The early workers were unaware of the great gulf between the reproductive and other systems of the monotremes (discovered about 1790), the marsupials (opossums discovered in the sixteenth century and the Australasian forms about 1760), and the placentals (the only mammals really well-known until the nineteenth century), and thus the basis for primary subdivision of the Mammalia was unlike that now universally accepted. The eighteenth century naturalists were invariably misled by the convergence of marsupials with different placentals. The unity of the Marsupialia was finally noted by De Blainville (in 1816) who united them as "didelphes normaux" and proposed three subclasses of mammals: the monotremes, marsupials and placentals (Simpson 1945, p. 164, 170). Thus the Marsupialia are not just a whim of the evolutionists. The group was originally created by pre-evolutionary biologists.
Besides their reproductive system and embryology, marsupials share many details of skull, teeth and skeleton. Paleontologists can identify marsupial fossils by these means and any good anatomist can distinguish a skull of a dog from that of a tasmanian wolf (Carroll, 1988, p. 430). All of the resemblances between various marsupials and placentals are adaptations related to various similar ecological ways of life. Consideration of anatomy, physiology, cytology, electrophoretic and serological studies all indicate that the marsupials are a natural taxon (Archer, 1984).
In the caption to Pandas' Figure 5-2, it is claimed that the wolf skull is nearly identical to that of the Tasmanian wolf and much less similar to that of the dog. The accompanying text claims that the two wolves are "superficially almost identical." Actually, by looking carefully at the drawings of the three skulls, it is obvious that the dog and wolf share more specific features that the wolf and the Tasmanian wolf. One of the convergent similarities of the two forms is the carnassial teeth, the broad blade-like teeth in the upper and lower jaws that acts like scissors to slice flesh. In the wolf and dog (as in all placental carnivores) it is the last upper premolar and the first lower molar that are so modified. The other molars are reduced in size and act as crushing teeth. In contrast it is the last four molar teeth in both jaws of the Tasmanian wolf that are modified as carnassials. Clearly the carnassials of placental carnivores and the Tasmanian wolf are not homologous. In addition, the skull of the Tasmanian wolf has four molars (placentals never have more than three), only three premolars (placentals have up to four), holes in the palate, posteriorly expanded nasal bones, an alisphenoid tympanic wing flooring the middle ear, the involvement of the jugal at the edge of the glenoid fossa for articulation of the lower jaw, broad extension of the lachrymal bone onto the face of the skull and mesially enlarged angular process of the dentary (lower jaw), features which it shares with most other marsupials (Archer, 1984). In addition, the teeth appear to be homologous to the placental milk teeth; the only marsupial tooth that is replaced in life is the third premolar. Taking all these characters together, anyone can easily distinguish between the skulls of a wolf and thylacine (Figure 5.1). Denton's claim (Denton, 1986, p. 178) that only a skilled zoologist can distinguish them is nonsense.
Of course, the Tasmanian wolf has the reproductive anatomy, physiology and embryogeny characteristic of all marsupials. Like all other marsupials, it has a relatively small brain with no corpus callosum connecting the two cerebral hemispheres and exhibits no pack or herd organization (Bergamini, 1964, pp. 80, 84). At most it hunted in pairs. Finally, serological tests based on albumen recovered from dried museum skins (the Tasmanian wolf is extinct, the last known live specimen died in the Hobart zoo in 1934) indicate that it is closely related to another groups of Australian marsupials, the dasyurids (Archer, 1984; Sarich et al, 1982). In general proportions it is similar to dasyurids and differs from the wolf in virtually all structural features relating to the pursuit carnivore role (Keast, 1982). The live Tasmanian wolf, with its striped back, long tapered tail and relatively short legs, looked like a strange wolf indeed (see Park, 1985). All biologists, including the pre-evolutionary 19th century anatomists classified the Tasmanian wolf as a marsupial. Pandas gives the impression that there is something wrong with this classification—that it is an arbitrary evolutionist whim—but never explicitly gives an alternate creationist view.
The similarities of the Giant and Lesser Pandas are related to their similar ecologies (feeding on bamboo). The fact that their ancestors, bears and racoons, are themselves relatively closely related, made the analogies and homologies difficult to untangle (see Gould, 1986a; Mayr, 1986; O'Brien, 1987 for a historical review). Footnote 2 (p. 118) refers to Davis (1964). But what of the Panda's thumb (Pandas' Figure 5-6 on p. 120 is somewhat distorted. Compare it with the diagram in Gould, 1978 or Gould, 1980, p. 22). If an intelligent designer is indeed working from a small vocabulary of forms (Pandas, p. 133), why didn't it give the panda an efficient opposable thumb as it did the Primates?—instead of the marginally efficient enlarged radial sesamoid bone! The lesser panda doesn't have a "thumb" (Mayr, 1986, p. 770). Similarly, a really intelligent designer would have endowed the panda with enzymes to digest cellulose and lignin. As it is, the pandas digestion is only 17% efficient and individuals must spend 10 to 12 hours a day eating in order to process enough bamboo to sustain themselves (Gould, 1980; Schaller et al, 1989). (Similarly the intelligent designer would have given cows such enzymes instead of the complex stomach and complex bacterial fermentation process that they actually have!) Incidentally, Pandas' Figure 5-5 portrays the undersides of several skulls (which include the upper jaws), not just the upper jaws themselves!
Three different and independent molecular techniques (DNA-DNA hybridization, isozyme genetic distance based on more than 50 loci and immunological distance of serum proteins support the conclusion that the giant panda is related to the bears (O'Brien et al, 1985; O'Brien, 1987). Bears have 74 acrocentric chromosomes (the centromere is at one end) while the giant panda has 42 large metacentric (the centromere is in the middle) chromosomes each with two arms. Although the chromosome count for the giant panda is closer to that of the lesser panda (Pandas, p. 119, bottom), using G-trypsin banding technique, nearly every bear chromosome could be aligned with a giant panda chromosome arm, whereas only two of the giant panda or bear chromosomes had recognizable counterparts in the lesser panda or racoon. On the other hand 14 chromosomes of the lesser panda were strikingly homologous to chromosomes found in several procyonids (O'Brien et al, 1985; O'Brien, 1987).
The biochemical evidence indicates that the lesser panda is related to the Procyonidae (racoon, etc.) which, in turn, is the family closest to the Ursidae (the bears). Figure 5.2 summarizes these relationships in a phylogenetic tree. Probably the morphological similarities of the two pandas result from the parallel retention of ancestral characters that may have been later lost by the bears (O'Brien et al, 1985; Wayne et al, 1989). The lesser panda may occupy an intermediate position between the procyonids and ursids (Wozencraft, 1989a, p. 515; Wozencraft, 1989b, p. 579). Although Pandas points out that the giant panda doesn't hibernate, that doesn't mean very much. The only bears that hibernate are the black, brown and grizzly bears of north-temperate America and Eurasia. The asiatic black bear of southern and eastern Asia may or may not hibernate depending on the severity of the weather; the spectacled bear of South America, the sloth bear of India, the sun bear of southeast Asia, and the polar bear do not hibernate (Walker, 1975). What fossils there are indicate that the giant pandas evolved from the bears and the lesser panda is related to the procyonids (Mayr, 1986).
Pandas tries to discredit the homology of the mammalian ear bones and the therapsid jaw joint. This is, in fact, one of the most thoroughly documented and incontrovertible examples of homology (Gould, 1990). It is based on extensive morphological, embryological and fossil data. For a detailed discussion of the similarity of connections of these bones with other bones, muscles, nerves and blood vessels, see Goodrich (1958). The homology was first proposed by the German embryologist Reichert in 1837 (Goodrich, 1958) on the basis of the identical embryological beginnings of the reptilian articular and quadrate bone and the mammalian malleus and incus. In a sense, the marsupial embryo recapitulates the transformation: in the early embryo, the elements serve as a reptilian type jaw joint; when the dentary bone eventually contacts the squamosal bone of the skull and establishes mammalian jaw joint, these elements move into the middle ear and take up the function of the ear bones! There is extensive fossil documentation of the steps leading up to the final transformation among the latest therapsids and the earliest mammals. For more details, see the supplement: The Reptile-Mammal Transition.
Palaeontological judgments may be more subjective when specimens are incomplete and the animals are quite different from known living forms. Otherwise the identification of individual bones can be quite definite, especially since the differences are due to modifications of the same basic skeletal parts characterizing the vertebrate groups and not to radically different skeletal designs.
Pandas' Footnote 3 relating to fossilized dinosaur eggs is to Horner and Gorman, (1988, pp. 163-165). Paleontologists (evolutionary or not) working on fossil mammals deal mainly with teeth, jaws, skulls and post-cranial skeletal material, but not with "general external anatomy". Were the Pandas' authors half-asleep when they wrote that sentence beginning at the bottom of the first column on p. 122?
According to Pandas, the design proponent explains analogous features on the basis of design requirements. But so does convergent evolution, except that natural selection is responsible for "designing" the structures that meet the requirements for a particular function, not a supernatural creator. If a creator were responsible, we would expect the designs to be much more similar; the flesh-slicing teeth of the placental and marsupial wolves would be formed from the same (homologous) teeth. (Why would such a creator makes two groups of wolves with different reproductive systems? Or for that matter three different types of flying vertebrates? Surely there would be one best design for a wing!) Animals best adapted to flying through the air or swimming in water are those whose structures most closely satisfy aerodynamic and hydrodynamic requirements.
Again Pandas brings up a confusing discussion of marsupials versus placentals. We have already seen that there is a great deal of anatomical evidence for separating the two major groups. This was first done by early 19th century pre-evolutionary anatomists, not evolutionists. Would design proponents want to change the classification? Exactly what is their position concerning marsupials? If both creationists and evolutionists agree that there are marsupials and placentals, there must be some objective reasons for making the distinction!
As has already been pointed out, evolutionary biologists empirically determine homologies using the same evidence that pre-evolutionary biologists did. Obviously this does not entail assuming evolution to be true! Pre-evolutionary 19th century biologists created the group Marsupialia based on a large number of homologous structures. Evolutionary biologists explain the existence of those homologies on the basis of common ancestry. No circular reasoning is involved.
The alternative is that marsupials and placental were designed that way; that the designer decided to have two kinds of mammals (ignoring for the sake of simplicity, the monotremes as a third kind of mammal.) Pandas cannot come up with any reason for the designer's action. The authors admit that the designer's reasons will not be obvious to us, but they claim that such concepts will generate scientific research. What possible lines of scientific research can investigate the thoughts and motives of a supernatural creator? None. Intelligent design (creationism) is a completely sterile doctrine. It offers no understanding of the nature of the designer or how it (or they) decide(s) what to design and why or by what processes designs are made into reality. Thus it offers no explanations. The "intelligent design explanation" is the same as "supernatural explanation". Both are oxymorons. They are not explanations but statements saying that explanations are impossible and beyond human understanding. The NASA search for extraterrestrial intelligence and the archaeologist's recognition of the intelligent design of artifacts deal with natural, not supernatural intelligences, which can be investigated by science. All creationists, however, adamantly insist that their creators/designers are supernatural, hence religious mysteries, not scientific explanations.
This section does little to answer the question in the section title! It simply reiterates the vague and false criticisms presented earlier. Pandas insist that some homologies are farfetched (ex: the ear ossicles) and cite a number of other alleged difficulties without giving any examples. (If the ear ossicles are not homologous, how do the design proponents explain their embryogeny, especially in the marsupials?)
Homology is the main tool used by taxonomists (including cladists) to create biological classifications. It is certainly not used "very selectively and subjectively, when it can be applied at all." This is just as true of the 19th century pre-evolutionary biologists as it is of evolutionary biologists. The concept can be applied in an objective manner and it is not dependent on evolution. After all, the concept was invented by non-evolutionists. As pointed out at the beginning of this chapter, the early 19th century biologists applied the concept of homology across all vertebrates, not just to those closely related as the design proponents would limit it.
The resolution of the panda relationship question (Davis, 1964; O'Brien et al, 1985; see also Mayr, 1986) was a triumph for the methodology of evolutionary biologists based on the concept of homology. We are not given any alternative method of investigating the question by the design proponents. Presumably the designer/creator(s) made bears, pandas and racoons the way they are because that's the way it/they desired to do it!
It is claimed that chimps and starfishes have no common ancestry but Hawaiian fruit flies do! What objective criteria do the design proponents use to decide such a question? In more traditional creationist terms, how does one go about discovering the boundaries of a kind? How much evolution can a kind display? Pandas sidesteps this critical question on p. 78. Certainly the originally designed kinds would not be artificial human groupings. How much evolutionary modification can go on within a kind? It we can't determine this, and cannot know the possible extent of a kind, how can we decide which animals are related and which are unrelated and when it is legitimate to apply the concept of homology?
The 19th century morphologists discovered that the early stages of embryological development are much more similar than the adult forms. The facts were generalized in at least two ways: von Baer's laws and recapitulation. These ideas originated in a nonevolutionary (creationist) context and only later were given evolutionary interpretations. All the morphologists used the similarities of embryos in sorting out homologies and establishing their archetypes. Louis Agassiz was a creationist champion of recapitulation while Ernst Haeckel gave it an evolutionary interpretation. Pandas' Footnote 4 refers to Haeckel (1866). Clearly, recapitulation is not exclusively an evolutionary concept as implied by the title of this section!
Recapitulation has been shown to be untenable by 20th century embryologists and the similarity of embryos is explained differently, i.e. most evolutionary changes in development occur in later stages. The early stages are so intertwined with webs of induction coordinating these initial stages that it is almost impossible to make changes without destroying the system. Thus the early stages, for example, are hardly different from those of the ancestral fishes. (See the supplement Embryos And Evolution for more details, including vestigial organs).
Pandas is thus more than 60 years out of date(!) when it insists on discussing the embryological evidence in terms of recapitulation. Human embryos do develop a tail that in the 5th week is one sixth the length of the embryo and contains a number of somites (incipient vertebrae). During the next four weeks, it disappears from external view, partly through actual regression. The coccyx, the remnant of the tail, recedes to a higher position in relation to the buttocks. The coccygeal fovea, or postanal pit, of a newborn marks the site where the coccyx disappeared below the surface. (Arey, 1946, p. 184; Gould, 1982 for a photo). Why should an intelligent designer give the human embryo a temporary tail to make a coccyx which then has to move to the proper place to be the point of attachment for some muscles?
Isn't it strange that an intelligent designer would provide the human embryo with three different sets of excretory organs?
Pandas' discussion of The Skeleton: A Hard Case for Recapitulation rests on incorrect data. The earliest ostracoderm fishes had heavy and complete coat of dermal bony armor. The dermal or membrane bones of modern forms are not preceded by cartilage but develop directly within blastemal (i.e. mesenchymal) sheets (Arey, 1946, p. 365). Also none of these earliest fossil fishes show signs of endoskeletons. They may have had cartilaginous endoskeletons, but cartilage normally doesn't fossilize. Only by the upper Silurian period do we find ossified internal skeletons (Carroll, 1988, p. 35). Thus the fossil evidence is not at odds with what one might have expected on the basis of recapitulation.
Pandas' conclusion (p. 133) that homology appears to be an unreliable concept, and that the evidence for evolution from comparative anatomy and embryology is weak and misleading is totally unwarranted and erroneous! Furthermore, if homology is an unreliable and essentially worthless concept, why do the design proponents embrace it and boast that it was originated long before Darwin (p. 133).
The idea of a "small vocabulary of forms" used over and over again by the designers is a totally ad hoc hypothesis that does not explain the "grand design" discovered by the early anatomists. True, designing by random selections from a bag of tricks would not only leave in disarray our efforts to trace evolutionary relationships, (which they aren't) but would make a hierarchic classification impossible (which hasn't happened either.) How does this concept explain why the panda wasn't given a real thumb? or enzymes to digest bamboo? or why the wings of pterosaurs, birds and bats are different? Or why the enzyme cytochrome C (see chapter 6) isn't identical in all forms? When you try to use it, it becomes clear that it doesn't explain the way things really are.
It is true that classification has not much changed by the acceptance of evolution. Both the evolutionary and pre-evolutionary taxonomists based their classifications on perceived homologies. Many of the latter recognized the same homologies and analogies that evolutionists do. It is just the interpretation of those homologies that differ—indicating common descent instead of the features of a type or archetype. Thus Darwin said, ". ..systematists will be able to pursue their labours as at present." (Darwin, 1968, p. 455).
Distinguishing between similarities due to homology, convergence, and parallelism, guided by the principles of conservation of ancestral characters and irreversibility—"These are the most important principles that validate and guide phylogenetic grouping by morphological characters-in-common, the modern equivalent of archetypal grouping, sometimes so similar to the latter in appearance as to be mistaken for it but fundamentally different in principle." (Simpson 1945, p. 11).
Comparing the first edition of Gegenbaur's great textbook of comparative zoology (published in 1859 just before the Origin) with the second edition, published 11 years later reveals remarkably little difference except that terms like "morphological type" or "archetype" were replaced by "common ancestor" (Mayr, 1982).
The Pandas references to cladists (pp. 127, 133) are misleading. Cladistics was introduced to biologists by the German entomologist Willi Hennig in a 1950 book. His goal was an objective method for reconstructing phylogenies and achieving Darwin's prediction that classifications should become ‘genealogies.'. It was a response to the widespread habit, among biologists and palaeontologist, of classifying organisms on the basis of heterogeneous criteria (morphological, ethological) and according to their overall resemblance and subjectively determined degree of divergence. Previous classifications often reflected the importance or weight given somewhat subjectively to various characters by the taxonomist.
Cladists attempt to discover evolutionary branching sequences by identifying shared derived characters—homologous similarities uniquely present at a branching point. (Janvier, 1984; Luria et al. 1981. pp. 679-682; Patterson, 1978, pp. 125-127) All taxonomists rely on similarities and differences among organisms! (Luria et al, p. 670 fol.) Some cladists (‘transformed' or ‘pattern' cladists) try to make their methods and procedures independent of evolutionary theory so that the patterns they find (cladograms) can be used as independent and falsifiable tests of evolutionary hypotheses, not because they want to give nonevolutionary interpretations of them! They were originally prompted to make cladistics independent of evolution because of their misinterpretation of statements made by the philosopher of science, Karl Popper (and later repudiated by Popper) that Darwinism was untestable. See Charig, 1982 for a lucid account of the philosophy of transformed cladistics and Sonleitner, 1896 for the views of Karl Popper. Also, cladistic methodology is designed to work with extant living forms. If a fossil form is included in the analysis, it can only be accommodated as a sister taxon and not as an ancestral form. This may be the basis for the quotation from Patterson (a pattern cladist) at the end of excursion Chapter 4.
Archer, M. 1984. Origins and early radiations of marsupials. In: Archer, M and G. Clayton. Vertebrate Zoogeography and Evolution in Australasia. Hesperian Press. pp. 585-626.
Arey, L. B. 1946. Developmental Anatomy: A Textbook and Laboratory Manual of Embryology. 5th Edition. W. B. Saunders Company.
Bergamini, D. 1964. The land and wildlife of Australia (Life Nature Library). Time Inc. N. Y.
Carroll, R. L. 1988. Vertebrate Palaeontology and Evolution. W. H. Freeman and Co. N.Y.
Charig, A. J. 1982. Systematics in Biology: A Fundamental Comparison of Some Major Schools of Thought. In: Joysey, K. A. and A. E. Friday (Editors). Problems of Phylogenetic Reconstruction. Academic Press, N. Y. pp. 363-440.
Darwin, C. 1968. The Origin of Species. (reprint of 1859 Edition) Penguin Books
Davenport, G. (Editor) 1983. The Intelligence of Louis Agassiz: A specimen book of scientific writing. Greenwood Press, Publishers. Westport, Connecticut
Davis, D. D. 1964. The Giant Panda: A morphological study of evolutionary mechanisms. Fieldiana. Zoology Memoir 3. Chicago Natural History Museum.
Denton, M. 1986. Evolution: A Theory in Crisis. Adler and Adler.
Forey, P. 1982. Neontological Analysis Versus Paleontological Stories. In: Joysey, K. A. and A. E. Friday (Editors). Problems of Phylogenetic Reconstruction. Academic Press, N. Y. pp. 119-157.
Goodrich, E. S. 1958. Studies on the structure and development of vertebrates. 2 vols. (reprint of an 1895 book). Dover Publications, Inc.
Gould, S. J. 1978. The Panda's Peculiar Thumb. Natural History 87(9): 20-30. (November).
Gould, S. J. 1980. The Panda's Thumb: More reflections in Natural History. W. W. Norton & Co. N. Y.
Gould, S. J. 1982. Fascinating tails. Discover 3(9):40-41 (September).
Gould, S. J. 1985. A clock of evolution. Natural History (April): 12-25.
Gould, S. J. 1986a. Fuzzy Wuzzy was a bear. Andy Panda, too. Discover 7(2): 40-48 (February).
Gould, S. J. 1986b. Archetype and Adaptation. Natural History (October): 16-27).
Gould, S. J. 1988. The heart of terminology. Natural History (February): 24-30.
Gould, S. J. 1990. An Earful of Jaw. Natural History (March): 12-23.
Haeckel, E. 1866. General Morphology of Organisms. Georg Reimer, Berlin.
Horner, J. R. and J. Gorman. 1988. Digging Dinosaurs. Workman Pub. Co. N. Y. pp. 163-165.
Janvier, P. 1984. Cladistics: Theory, purpose, and evolutionary implications. In Pollard, J. W. (Editor). Evolutionary theory: Paths into the Future. pp. 39-75.
Luria, S. E., S. J. Gould and S. Singer. 1981. A View of Life. The Benjamin/Cummings Pub. Co.
Keast, A. 1982. The thylacine (Thylacinidae, Marsupialia): How good a pursuit carnivore? In: Archer, M. (Editor). Carnivorous Marsupials (2 volumes). Royal Zoological Society of New South Wales. pp. 675-684.
Mayr, E. 1963. Animal Species and Evolution. The Belknap Press of Harvard Univ. Press.
Mayr, E. 1982. The Growth of Biological Thought: Diversity, Evolution and Inheritance. Belknap Press of Harvard University Press. (see pp. 455-469).
Mayr, E. 1986. Uncertainly in science: Is the giant panda a bear or raccoon? Nature 232:769-771.
O'Brien, S. J. 1987. The Ancestry of the Giant Panda. Scientific American 257(5): 102-107 (November).
O'Brien, S. J., W. G. Nash, D. E. Wildt, M. E. Bush and R. E. Benveniste. 1985. A molecular solution to the riddle of the giant panda's phylogeny. Nature 317: 140-144.
Park, A. 1985. Is this toothy relic still on the prowl in Tasmania's wilds? Smithsonian 16(5): 117-130 (August).
Patterson, C. 1978. Evolution. British Museum (Natural History) Cornell Univ. Press.
Patterson, C. 1981. Significance of fossils in determining evolutionary relationships. Annual Review of Ecology and Systematics 12: 195-223.
Sarich, V., J. M. Lowenstein and B. J. Richardson. 1982. Phylogenetic relationships of the thylacine (Thylacinus cynocephalus, Marsupialia) as reflected in Comparative Serology. In: Archer, M. (Editor). Carnivorous Marsupials (2 volumes). Royal Zoological Society of New South Wales. pp. 707-709.
Schaller, G. B., T. Qitao, K. G. Johnson, W. Xiaoming, S. Heming and H. Jinchu. 1989. The Feeding Ecology of Giant Pandas and Asiatic Black Bears in the Tangjiahe Reserve, China. In: Gittleman, J. L. Carnivore Behavior, Ecology, and Evolution. Comstock Publishing Associates. pp. 212-241.
Simpson, G. G. 1945. The Principles of Classification and a Classification of Mammals. Bulletin of the American Museum of Natural History 85:1-350.
Simpson, G. G. 1961. Principles of Animal Taxonomy. Columbia Univ. Press. N. Y.
Smith, M. 1982. Review of the thylacine (Marsupialia, Thylacinidae). In: Archer, M. (editor). Carnivorous Marsupials (2 volumes). Royal Zoological Society of New South Wales. pp. 237-253.
Sonleitner, F. J. 1986. What Did Karl Popper Really Say About Evolution? Creation/Evolution 6(2):9-14
Walker, E. P. 1975. Mammals of the World, 3rd Ed. (2 volumes). Johns Hopkins University Press.
Wayne, R. K., R. E. Benveniste, D. N. Janczewski, and S. J. O'Brien. 1989. Molecular and Biochemical Evolution of the Carnivora. In: Gittleman, J. L. Carnivore Behavior, Ecology, and Evolution. Comstock Publishing Associates. pp. 465-494.
Wozencraft, W. C. 1989a. The Phylogeny of the Recent Carnivora. In: Gittleman, J. L. (Editor). Carnivore Behavior, Ecology, and Evolution. Comstock Publishing Associates. pp. 495-535.
Wozencraft, W. C. 1989b. Classification of the Recent Carnivora. In: Gittleman, J. L. (Editor). Carnivore Behavior, Ecology, and Evolution. Comstock Publishing Associates. pp. 569-593.
(from Frank Sonleitner's critique of Of Pandas and People)
Outline of the Pandas Chapter
Pandas describes the basic similarities of organisms at the cellular and biochemical level.
Pandas fails to point out that many different amino acid sequences will produce the same three-dimensional folding pattern (Lau and Dill, 1990) as will be demonstrated with the cytochrome c enzyme. Also, the "remarkable" feature that proteins in living cells all contain only left-handed amino acids, probably results from the fact enzymes (organic catalysts) are involved in protein production and enzymes are very sensitive to the three-dimensional shape of their substrates. The same can be said for the right-handedness of the sugars in nucleic acids.
Here Pandas does point out that all eukaryotic organisms have the same complex molecular machinery (of which cytochrome c is a part) in their mitochondria. There are, however, known variations of certain pathways in various organisms. Anaerobic metabolism in yeast, for example, produces ethyl alcohol instead of lactic acid. Also different compounds may be used for similar functions in various organisms. For instance, a variety of respiratory pigments, which increase the oxygen carrying capacity of blood, are found in animals. They include the familiar haemoglobin, the green iron pigment chlorocruorin found in several families of polychaete worms, the violet/pink iron pigment haemoerythrin found in some sipunculids, polychaetes, priapulids and brachiopods and the blue copper pigment haemocyanin found in some crustaceans, the horseshoe crab and molluscs (Brusca and Brusca, 1990). In general, modern research shows that the Protoctista (Protista) exhibit so much biochemical diversity that nearly 20 kingdoms(!) ought to be created to accommodate them (Margulis and Schwartz, 1982). Even greater biochemical diversity exists among the Prokaryotes. The viruses exhibit every conceivable variation on nucleic acid structure in their hereditary material (Joklik, 1974). There are even variations in the genetic code found in mitochondrial DNA (Jukes, 1983). (Actually, uniformity of the genetic code is a weak argument for a designer. Most computer manufacturers use what is called the ASCII code for representing information in their computers, yet IBM uses an entirely different and incompatible code (EBCDIC) for the same purpose.)
Design proponents attempt to explain biochemical similarities as a requirement for efficient functioning of the food chain. The designer must have forgotten this requirement when it forgot to endow most of its herbivorous designs with an enzyme to digest cellulose and lignin, making herbivore digestion very inefficient and complicated. But why have a food chain? There is nothing comparable among human design products. And you can have a viable ecosystem with just microorganisms. Multicellular animals and plants are superfluous. The adaptations of predators and prey are like an arms race among weapons manufacturers. But the designers of a counter-weapon are not the same designers that designed the weapon. They usually work for a different company and a different nation. By analogy, it would follow that there are different designers for predator and prey organisms. There is obviously an intense rivalry among these biological designers, given the fantastic array of predators and parasites and the strategies, bordering on the fiendish and diabolical, that they use to catch and eat their prey! More than half the known species of animals are parasites on other living animals (Price, 1977). Some of these design rivalries are bizarre. Even Darwin couldn't imagine an intelligent designer designing tens of thousands of species of insect parasitoids, that eat their living hosts from the inside.
The metabolic pathways in organisms are long with many involved steps and unexpected complexity. Even the process of blood coagulation involves a labyrinthine series of about 10 steps, resembling more closely a biochemical Rube Goldberg apparatus than an intelligent, rationally designed mechanism. These pathways are more consistent with the operation of a tinkerer, rather than the intelligent design of an engineer. And natural selection can only operate as a tinkerer, modifying entities that already exist (Jacob, 1977).
As Pandas correctly states, similarities in molecular sequences, whether they be sequences of nucleotides in DNA or amino acids in proteins, provide a large array of new characters which can provide homologies expressed quantitatively. These homologies can then be used to erect classifications of organisms.
Pandas immediately tries to discredit the use of molecular sequences, claiming that the computer programs construct evolutionary trees by "massaging" the data (whatever that means) with evolutionary theory. Even then such programs generate a number of different trees consistent with the same data. Evolutionists then "choose" the "best" tree to be presented as the final result (see Pandas' Figure 6-3). How true are these allegations?
Fitch and Margoliash (1967) generated an evolutionary tree using data on cytochrome c sequences from 20 different organisms representing a wide range of groups. The tree is presented here as Figure 6.1. The 20 organisms are almost the same as the 25 presented in Pandas' Figure 6-6 (p. 141) and the 19 in their Table 6-1 (p. 142). The main objective of the paper was to present the method of constructing the tree. The method involves the following steps:
Thus Pandas' Figure 6-3 is incorrect. The data are not "massaged" with evolutionary theory and the "correct" trees are not chosen on the basis of other data. As Fitch and Margoliash point out (middle of column 3 on p. 283 of their paper), the method makes no assumptions about the rate at which mutations have accumulated, that is, no assumptions about a molecular clock are involved. The same is true of Farris' distance-Wagner method (Farris, 1972).
This tree "is remarkably like that constructed in accord with classical zoological comparisons" (Fitch and Margoliash, 1967). Again, it is not based on evolutionary theory. If protein sequencing data and computers were available to the early 19th century biologists, they might have used the very same technique, although the results would have been presented as a hierarchical classification, rather than as an evolutionary tree. Farris (1972) discusses the variety of methods used to construct phylogenetic (evolutionary) trees from biochemical distance matrices. Most of these are based on numerical taxonomy techniques and phenetic similarities which are independent of evolution (Fitch and Margoliash, 1970). Although many of the methods generate "ancestral nodes" (branching points on a tree), Owen would say they represented "Types." Penny et al (1982) present a technique, using graph theory, that could even refute the existence of an evolutionary tree. Avers (1989, p. 347 fol.) gives a good introduction to the methods of constructing trees.
Pandas notes that the cytochrome divergence patterns resemble that depicted by traditional taxonomy. Pandas further says (p. 142) that this is what one would expect on the basis of the evolutionary viewpoints and would be a striking confirmation at the molecular level of Darwinian evolution! It is at this point that Pandas introduces the utterly unjustified and nonsensical concept of evolutionary sequence of living forms in a desperate attempt to discredit this evidence for evolution.
Pandas puts these living forms (which are at the tips of the tree shown in Figure 6.1) into a straight line sequence (shown in their Table 6-1) and claims that the molecular patterns do not follow a pattern of intermediate sequences, but instead a pattern as shown in their Figures 6-9 through 6-14 and hence the data refute evolution!
Of course the straight-line evolutionary "sequence" shown in their Table 6-1 is nonsense. No evolutionist ever suggested that the Rhesus monkey evolved from the Rabbit, the Horse from the Chicken, the Chicken from the Turtle, the Tuna from the Screw Worm, the Silkworm from the Sesame plant or Mung Beans from Yeast, to mention only a few of the inanities embodied in this table. Evolutionary relationships follow a branching pattern (as in all evolutionary trees), not a straight line sequence).
All the life forms considered in the cytochrome c database are present-day living forms hence none are ‘more primitive' or ‘transitional stages' between others. They are all on the tips of the twigs of an evolutionary tree. The only forms that are truly transitional and would make a true evolutionary ‘series' would be forms that lived in the past and exist now only as fossils. The bullfrog (Pandas' Figure 6-11) is a highly advanced and specialized amphibian. The amphibians that were actual transition forms between fishes and reptiles existed in the late Paleozoic Era. Any intermediate cytochrome sequences would have to come from these actual ancestral forms which, unfortunately, only exist as fossils (Pandas actually mentions this on p. 149!).
The patterns depicted in Pandas' Figures 6-9 through 6-14. correspond to the common branching points on the tree shown in Figure 6.1. This is clearly shown in Figure 6.2 where an evolutionary tree is superimposed over Pandas' Figure 6-14. This has been pointed out repeated by evolutionists as the fundamental error committed by Michael Denton in his book: Evolution: A Theory in Crisis from which Pandas' Chapter 6 has been taken (Landau, 1989; Scott, 1990; Schadewald, 1990; Sonleitner, 1990; Thwaites, 1989). Thus Pandas' biochemical argument against evolution is totally without any logical or biological foundation. One wonders how Denton and the creationists (sorry, design proponents), which include at least one with biochemistry training, could have committed such a gross error. It says little for their intelligence and/or veracity. Or their consistency—on p. 142, the similarity of the cytochrome c pattern to the traditional taxonomic arrangement is said to be a striking confirmation of evolution; on p. 146-147 this same pattern is said to totally refute evolution! In spite of the total invalidity of this argument, it has been presented with glee(!) in many creationist publications (ex: Pearcey, 1989).
Pandas shows a similar pattern derived from hemoglobin in their Figure 6-15 showing an equal amount of divergence of a number of animals from the snail and claims: "This fact would not have been predicted by any informed scientist with an evolutionary frame of reference." That claim could not be more wrong! Pandas further claims that these data "show how false is the notion that advances in molecular biology are continually confirming evolutionary theory." In the following sections I will show that the molecular data are a brilliant confirmation of evolution but also that, contrary to Pandas, intelligent design (creationism) cannot explain these data!
Cytochrome c performs the same function in all organisms. It is found in the mitochondria (except in the prokaryotic bacteria) and is a part of the electron transport system which functions in aerobic respiration. Cytochrome c accepts electrons from a complex built into the mitochondrial membrane called cytochrome reductase and gives up the electrons to another complex, cytochrome oxidase (Dickerson, 1980). It consists of a chain of 104 amino acids folded into a three-dimensional structure bound to a heme group. Although there are differences in the sequence of amino acids in the various organisms (see Dayhoff, 1969; Dickerson, 1972; Dickerson, 1980 for the actual sequences), all versions have the same three-dimensional shape, even the cytochrome c from humans and Neurospora which differ in 44 of the 104 positions. To further illustrate the functional equivalence of all these versions of cytochrome c, the cytochrome c from any organism reacts equally well in the test tube with the cytochrome oxidase from any other species (Dickerson, 1972).
Knowing the amino acid sequences and the three-dimensional configuration, we can understand fairly well the chemical role that each amino acid plays in forming the functional cytochrome c molecule (Dickerson, 1972). Amino acids differ in the chemical nature of their side chains. It is these that determine the role that an amino acid plays in the structure and functioning of the polypeptide. For example, the chain is folded so that oily hydrophobic side chains are on the inside and polar, hydrophilic side chains are on the outside. The positions of such amino acids in the chain is critical; they help make the chain fold properly. Any substitutions of these amino acids are always with amino acids with similar side chains. Many of the amino acids involved in the attachment to the heme group are invariant. On the outside of the molecule is a pattern of positive and negative regions that possibly play a role in the interaction with the cytochrome reductase and cytochrome oxidase complexes. Changes here always involve amino acids with similar charges. There are only a few positions where a wide range of amino acids may be found. Thus all the changes seen in the amino acid sequence are selectively neutral. They do not change the functioning of the molecule.
Cytochrome c then is an example of the neutral theory of molecular evolution (Kimura, 1979; Jukes, 1988; Gould, 1985). When mutant genes that are selectively neutral appear in a population, their frequency fluctuates at random. In time most of them disappear, but occasionally some of them spread through the population and become fixed with a frequency of 100 percent. During the course of time, such neutral mutations will accumulate in the population. Over long periods of time, the rate of accumulation will average out to a relatively constant value.
The above considerations are the basis for the idea of a molecular clock. The distance similarities shown in Pandas' Figures 6-9 to 6-13 support the idea that differences in the cytochrome c chain have accumulated at a steady rate (as Pandas admits on p. 147). Figure 6.3 (from Dickerson, 1972) plots the average difference in amino acid sequence between organisms on two sides of an evolutionary branch point, say, between reptiles and mammals (vertical axis) versus the time elapsed since the divergence occurred as determined by the geological record. This is done for four difference proteins. In each case the points fall close to a straight line, indicating a constant average rate of evolutionary change. Note that we are dealing with similar average rates on different branches of an evolutionary tree, not some deterministically fixed mutation rate as Pandas implies (p. 147).
Why do the different proteins in Figure 6.3 have different rates of change? These are not mutation rates per se but rates of fixation of neutral or harmless mutations. Our knowledge of the chemical structure and function of fibrinopeptides shows that they can tolerate many random changes, that is, a large proportion of the mutations will be neutral. A hemoglobin molecule has many more constraints and random mutations are five times more likely to be harmful than in fibrinopeptides, hence the rate of accumulation of harmless mutations is five times slower in hemoglobin. (For more information on the evolution of hemoglobin, see Perutz, 1964 and Zuckerlandl, 1965). A large fraction of the surface of cytochrome c is involved in interacting with the reductase and oxidase complexes; hence a much smaller proportion of mutations in cytochrome c are harmless and its observed rate of change is concomitantly slower. Since histone IV (a basic protein that binds DNA to the chromosome) changes very slowly, apparently very few random changes in its structure are tolerated (Dickerson, 1972).
When one realizes that the molecular clock concerns the rate of fixation of neutral or harmless mutations, Pandas' criticisms based on mutation rates and the existence of multiple molecular clocks can be seen to be irrelevant. And evolutionary changes that are the result of nonneutral mutations subject to natural selection will not occur at constant rates. There are problems with estimating molecular clock rates and testing the constancy of such clocks (see Scherer, 1990) but the evolutionary interpretation of sequence data is based on the neutral gene hypothesis and not on the related idea of a molecular clock.
Regardless of how well the molecular clock may keep time, if the differences in cytochrome c are due to accumulation of random, neutral mutations, then the similarities that say, all vertebrates share relative to insects, plants and bacteria, can only be explained by common ancestry! That makes these data direct evidence for evolution and not just another criterion for classifying organisms. A specific prediction of the evolutionary hypothesis is that "evolutionary trees" of the same organisms constructed from different protein sequences should be the same. The prediction has been upheld by the work of Penny et al (1982) using sequence data for 5 proteins from 11 species.
Similar evidence for common ancestry is provided by pseudogenes. These are copies of genes that have become nonfunctional as a result of mutations. Any subsequent mutations in such a gene are neutral as far as the organism is concerned and will neither be selected for or against. The finding of identical pseudogenes in different organisms is strong evidence for their common ancestry because the alternative, that each line suffered the same series of identical random mutations, is highly improbable (Max, 1986; Li, 1983).
Pandas' claims that the data from biochemistry shows that living things cluster around a basic pattern or type for each class of organism, without any intermediates from one type to another as shown in their Figure 6-14. We have shown how evolution explains that pattern, which is based exclusively on modern living organisms in our Figure 6.2. Why should this be the state of affairs if an intelligent designer or designers created organisms? Remember that the biochemical data show that cytochrome c is an enzyme performing an identical function in all the organisms considered and it does it under virtually identical chemical conditions in the mitochondria of all those forms (except, of course, the bacteria.) Thus if all these forms were created a short time ago by an intelligent, rational creator, cytochrome c should have an identical structure in all these forms! After all, it is almost an ideal example of one of a "small vocabulary of forms . . . limited by functional constraints" (p. 133), "discrete blocks" or "pre-assembled units" (p. 33) or "common means .. . to achieve similar functions" (p. 137) evoked by Pandas in a pitiful attempt to explain similarities. But it doesn't have an identical structure! As a consequence, it simply doesn't fit in with Pandas' conception of homology at the cellular level. Why is this enzyme different in the various classes?
Design proponents (creationists) can't explain these data! Even if they fall back upon a molecular clock model (the clock running about a million times faster than the evolutionists postulate), the expected results would be different. Since all these forms would be equidistant in time from their creation, they all should be equally different from one another (say 65% different). Thus the creationist is almost forced to assume that these differences in cytochrome c structure are somehow adaptive (functionally significant) in the various forms. But, as I have shown, all the biochemical evidence points to the fact that observed differences in structure are neutral and have no effect on the function of cytochrome C. (That, in fact, is what makes the molecular clock plausible.) They would also have to explain why different proteins give the same evolutionary trees as shown to be the case by Penny et al (1982). Thus, unless creationists fall back upon some form of theistic evolution, the results of protein sequencing provide some of the most significant evidence against intelligent design (creationism)!
All the "conclusions" of Pandas are false or irrelevant. Pandas "proves" that spontaneous generation is impossible, then claims that it occurred frequently throughout geological time (as instantaneous miraculous productions of new forms by designers). Biological organisms might exhibit some characteristics of manufactured things, but in basic ways they are fundamentally different. Changes are limited in experimental breeds because of the slowness of natural production of mutations. Increasing the mutation rate by radiation exposure makes further change possible. The fossil record does provide intermediate forms connecting the taxonomic groups. The patterns of similarity among organisms do not show what one would expect from common design by a single designer. And the molecular data, grossly misinterpreted by Pandas, do corroborate evolution and refute intelligent design! Furthermore molecular biology has shown that the hereditary material is full of extraneous copies, nonfunctional pseudogenes and other non-coding garbage, hardly the kind of "blueprint" that an intelligent designer would create. Throughout this critique, we have seen that "intelligent design" (creationism) is empty of explanatory power. The real phenomena do not even fit its alleged predictions.
Avers, C. J. 1989. Process and Pattern in Evolution. Oxford University Press.
Brusca, R. C. and G. J. Brusca. 1990. Invertebrates. Sinauer Associates, Inc.
Dayhoff, M. O. 1969. Computer Analysis of Protein Evolution. Scientific American 221(1): 86-95.
Dickerson, R. E. 1972. The Structure and History of an Ancient Protein. Scientific American 226(4): 58-72
Dickerson, R. E. 1980. Cytochrome c and the Evolution of Energy Metabolism. Scientific American 242(3): 136-153.
Farris, J. S. 1972. Estimating phylogenetic trees from distance matrices. American Naturalist 106: 645-668
Fitch, W. M. and E. Margoliash. 1967. Construction of Phylogenetic Trees. Science 155: 279-284.
Fitch, W. M. and E. Margoliash. 1970. The Usefulness of Amino Acid and Nucleotide Sequences in Evolutionary Studies. Evolutionary Biology 4: 67-110.
Gould, S. J. 1985. A Clock of Evolution. Natural History (Apr.): 12-25.
Jacob, F. 1977. Evolution and Tinkering. Science 196: 1161-1166.
Joklik, W. K. 1974. Evolution in Viruses. In: Carlile, M. J. and J. J. Skehel (Editors). Evolution in the Microbial World. Cambridge University Press.
Jukes, T. H. 1983. Evolution of the amino acid code. In: Nei, M. and R. K. Koehn (Editors). Evolution of Genes and Proteins. Sinauer Associates Inc. pp. 191-207.
Jukes, T. H. 1988. Molecular Evolution and Ancestry of Living Organisms. Creation/Evolution Newsletter 8(4): 5-7.
Kimura, M. 1979. The Neutral Theory of Molecular Evolution. Scientific American 241(5): 98-126.
Landau, M. 1989. Protein Sequences and Denton's Error. Creation/Evolution 9(2): 1-7.
Lau, K. F. and K. A. Dill. 1990. Theory for Protein Mutability and Biogenesis. Proceedings of the National Academy of Science USA 87: 638-642.
Li, W-H. 1983. Evolution of Duplicate Genes and Pseudogenes. In: Nei, M. and R. K. Koehn (Editors). Evolution of Genes and Proteins. Sinauer Associates Inc. pp. 14-37.
Margulis, L. and K. V. Schwartz. 1982. Five Kingdoms: An Illustrated Guide to the Phyla of Life on Earth. W. H. Freeman and Company.
Max, E. E. 1986. Plagiarized Errors and Molecular Genetics: Another Argument in the Evolution-Creation Controversy. Creation/Evolution 6(3): 34-46. (Issue XIX, Winter).
Pearcey, N. 1989. Echo of Evolution? The Revolution in Molecular Biology. Bible-Science Newsletter 27(12): 7-10.
Penny, D., R. Foulds and M. D. Hendy. 1982. Testing the theory of evolution by comparing phylogenetic trees constructed from five different protein sequences. Nature 297: 197-200
Perutz, M. F. 1964. The Hemoglobin Molecule. Scientific American 211(5): 64-76.
Price, P. W. 1977. General Concepts on the Evolutionary Biology of Parasites. Evolution 31: 405-420.
Schadewald, R. 1990. Bliss on Molecular Biology. NCSE Reports 10(4): 17.
Scherer, S. 1990. The Protein Molecular Clock: Time for a Reevaluation. Evolutionary Biology 23: 83-106.
Scott, E. C. 1990. Of Pandas and People (review). NCSE Reports 10(1): 16-18.
Sonleitner, F. J. 1990. Molecular Nonsense in the Bible-Science Newsletter. NCSE Reports 10(2): 14-15.
Thwaites, W. M. 1989. Evolution: A Theory in Crisis (review). NCSE Reports 9(4): 14-16.
Zuckerlandl, E. 1965. The Evolution of Hemoglobin. Scientific American 212(5): 110-118.
(from Frank Sonleitner's critique of Of Pandas and People)
Outline of the Pandas Chapter
Right from the start, Thaxton bombards the reader with misinformation about the fossil record. Only eight phyla of multicellular organisms that have extensive fossil records appear in the late Precambrian or early in the Paleozoic Era. The other phyla are represented by a few scattered fossils or none at all. This is a far different statement than that illustrated in Pandas' Figure 4.2! Vertebrate classes do not dominate the record, the shells of marine invertebrates are many times more abundant. Again the nonsense phrase "fully formed and functional" is used. As if evolution required that fossils of partially formed and nonfunctional organisms should be found!
In the third paragraph Thaxton makes a statement that completely undermines his efforts and arguments to make intelligent design a scientific hypothesis! He says that the view that "an intellect brought forth all similar structural features by natural means over time" is not considered by this book because this view is "empirically indistinguishable from natural descent". It follows that if Pandas' intelligent designers do not use natural means, they must be using unnatural or supernatural means. Thus the main distinction between evolution and creation (intelligent design) is natural versus supernatural, not natural versus intelligent. Hence creation (intelligent design) is not scientific but purely philosophical and/or religious (see Pandas, p. 160 fol.).
Thaxton claims that both "sides" deals with the same facts; that they only interpret them differently. The book clearly shows that this is not true. Most of the "facts" presented by Pandas are incorrect as this critique abundantly demonstrates. Creationists (intelligent design proponents) work in a world of imaginary facts fabricated by generations of creationist writers. Even the basic concepts are distorted. For example, Pandas radically redefines evolution as the transformation of kinds in Chapter 2.
Descent with modification results from a straightforward application of the principle of uniformity. Proponents of intelligent design do the opposite. They propose invisible, supernatural, untestable mechanisms working in the past totally unlike anything working in the present. Their "evidence" consists of wrongheaded and "imaginary" predictions about what evolutionists should find in the fossil record, such as "partial creatures".
Pandas certainly does not give us a clear and impartial presentation of the cases for both sides. As this critique shows in exhaustive detail, the information is clearly distorted and fabricated to make evolution look unlikely. For example, none of the relevant data supporting the homology of the reptilian jaw joint bones with the mammalian ear bones is presented. Quite the contrary, Pandas gives the reader the impression that this homology is purely "wishful thinking" on the part of the evolutionists to satisfy the requirements of evolution. There is extensive criticism of evolutionary mechanisms and ideas but virtually no criticism of the few vague intelligent design statements. There is no discussion at all of the radical differences between the old earth and young earth proponents. In fact, very little is said about "intelligent design". Most of the book is old-fashioned anti-evolution.
In science the method of multiple hypotheses means multiple natural testable hypotheses. Untestable supernatural hypotheses won't do.
Thaxton admits at the beginning of this "word to the teacher" that he and Pandas do not consider intelligent designers that work by natural means. Obviously, they only consider designers that work supernaturally. But as Thaxton correctly points out, the supernatural is not admissible in science. Neither are supernatural designers. Thus this entire argument trying to establish "intelligent" as an alternative to "natural" is totally irrelevant to the subject matter of Pandas and the question of intelligent design as a scientific hypothesis.
Thaxton's and Pandas' argument for intelligent design totally defies the principle of uniformity and has nothing in common with the thinking of archaeologists, forensic scientists, or people explaining "John loves Mary" written in the sand.
Intelligent causes are perfectly acceptable in science as long as they are natural intelligent causes. SETI is looking for intelligent biological organisms, not invisible supernatural intelligences.
Thaxton totally misuses the principle of uniformity. How do organisms originate and change? They reproduce themselves. We do not observe any kind of design or manufacturing process producing organisms at the present time, therefore we do not postulate such a process in the past. The idea that organisms were intelligently designed is not based on the principle of uniformity but on an analogy—organisms are like manufactured objects. This analogy is very weak and is rejected by all modern philosophers, including Hume, who proposed the principle of uniformity!
As I have already mentioned there are many other changes in the physiology and behavior of dark peppered moths and some biologists, such as Lovtrup, whose book is recommended by Pandas(!), considers this a macromutational change.
We know that the complex arrangements of matter we see in computers, literary works and bridges are the result of natural intelligent (human) causes. Thus we are justified in ascribing the existence of computers, literary works and bridges that were produced in the past to natural intelligent (human) causes. This is no basis for ascribing the complex order of organisms to supernatural intelligent causes of totally unknown and unknowable nature. Such an hypothesis is not only unscientific, it has a decidedly dampening effect on scientific research and tends to become a self-fulfilling prophecy. If all scientists believe that a phenomenon is supernatural and hence beyond understanding, none are not likely to devote time to research in an attempt to explain that phenomenon. They will move on to something else. And so that phenomenon will remain unexplained.
Darwin described natural selection in terms of an analogy with the artificial selection of breeders. We have now verified the existence of natural selection in nature. The principle of uniformity leads us to postulate that changes in organisms that we see in the fossil record also came about through natural selection. Also, since it has been empirically shown that all life comes from life, organisms in the younger layers of the geological sediments must have descended from those in the older layers. To postulate that this is not so and that those successive fossil faunas and floras were independently created is to reject the principle of uniformity!
The design proponents intelligent cause is not rooted in experience. We have never seen an organism being designed or created. Furthermore unless one postulates some sort of natural design mechanism, it cannot be considered by science. Only if we can postulate and understand how it works, can we possibly understand what it would and would not produce and hence test it. No matter how much the genetic code looks like a code, and how much you dress up the idea in information theory, a supernatural designer cannot be a scientific hypothesis.
We do not observe DNA encoded messages being produced by a designer. All DNA comes from previous DNA and changes are brought about by mutation. These observable causes for the origin of DNA have little to suggest "manufacture" by some invisible designer. Nor would postulating such an entity add anything to our understanding of the processes. There is no logical justification for Pandas' line of argument.
Thaxton admits that only design by supernatural means is considered by this book. Thus the natural/supernatural dichotomy remains and intelligent design and creationism has no explanatory power. No design explanations are given in the book—only repeated assertions that an intelligent agent was responsible. This does not provide any basis for predictions or testing of hypotheses. Because the agent works in a supernatural manner, which is to say the agent utilizes processes completely beyond human comprehension, we have no idea of what the agent could or could not do. In fact all creationists assume that the agent is omnipotent and omniscient, i.e. anything is possible.
Thaxton's assertion that the proper alternative to a natural cause in science is intelligent cause has no logical justification. Any intelligent causes considered by science operate by natural means. We know, understand, and can describe in detail, how people might write words in the sand or how pickup trucks are manufactured. Thus intelligent cause is a subdivision of natural cause. Because the aim of science is to discover explanations, not promulgate supernatural mysteries, it must restrict itself to natural causes. Thus if the student draws the Naturalistic conclusions that (1) Science includes only what is natural; and (2) Science does not include the supernatural, the student will be 100% correct! Science does not exclude natural intelligent causes but Pandas does!
The hallmark of intelligent design or creationism is supernatural cause. As has already been pointed out, Thaxton, himself says (p. 153) that a designer working by natural means over time is indistinguishable from evolution and is an alternative not discussed by this book! Virtually all creationists insist that their designer, creator or God works exclusively by supernatural means. The term "supernatural explanation" is an oxymoron, i.e. a contradiction in terms. To say that a phenomenon is supernatural is to say that it is beyond human understanding and incapable of being explained! Thus creationism, no matter what you call it, intelligent design, abrupt appearance, etc. has no explanatory power and is outside the scope of science.
Thaxton contradicts himself. He agrees that the science classroom is not an appropriate place to discuss the supernatural but at the same time he advocates presenting a supernatural intelligent designer! His entire case for the natural/intelligent dichotomy falls apart.
Unfortunately, students who read or study Pandas will fill their heads with incorrect or "imaginary" facts, distorted historical backgrounds and illogical and self-contradictory arguments. By Thaxton's own criteria, the supernatural intelligent designers of Pandas are outside the realm of science and have no place in the science classroom. Even if all the references to the supernatural intelligent designers were eliminated, the book would be unacceptable as a critique of evolution because of the wealth of misinformation and distortions that it contains.
The argument from design, championed by William Paley, was thoroughly critiqued by Hume in his work Dialogues Concerning Natural Religion and summarized by Water Kaufmann (Kaufmann, 1958. Critique of Religion and Philosophy. Harper and Bros., section 45) in a concise and witty manner. The argument is based on analogy and goes something like this: If you found a wristwatch, you would not hesitate to infer that it was made by a watchmaker. (My first inference would be that someone had lost it). The universe with its many complicated interrelated parts is like a watch, therefor you should infer that it was made by a "universe maker" who is (of course!) the Christian God. The logic of the argument is very weak. In fact the argument is about 5% logic and 95% contrivance. If you found a wristwatch similar to the one I'm wearing as I type these lines, you should more accurately infer that it was designed by a group of electrical engineers, its parts fabricated by very intricate processes in a factory and assembled, on a mass production basis, by a force of oriental housewives working on an assembly line in Taiwan or Japan. If we start with an automobile as our example, the process is even more elaborate. According to the Ford Motor Co. (Furnas, C. C., J. McCarthy and the Editors of LIFE. 1966. The Engineer. Time, Inc. p. 16), as many as 12,000 engineers contribute to the design of a modern auto, and the various parts are made in many factories.
Thus, preserving the analogy as closely as possible, we should infer that our universe was designed by an army of cosmic engineers, its parts fabricated by an entire industry of cosmic factories and assembled on a mass production basis by an army of cosmic workers (angels?) If we borrow the creationists' fondness for infinities, these factories have been working for eternity and there should be an infinity of universes! If you protest that this analogy is unfair; that prior to the nineteenth century, watches really were made by watchmakers, you would still not be quite correct. A watch, or most of it, was probably made by apprentices to the watchmaker!
Present day watches (and cars) are made in a variety of models—deluxe ones and cheap ones. What model of universe is ours? Maybe its a cheap model, even a lemon! If we seriously heed the creationists' insistence upon a universal law of death and decay, we may be dealing with either an example of the divine version of planned obsolescence or our universe should have been recalled to the factory for repairs. Indeed, it may already have been cast aside and is now "decaying away" on some cosmic junk heap.
The point is that the argument from design must be "forced" to lead us to a single, omnipotent and omniscient Christian God and hence is no "proof" at all of such a being, only an arbitrary exercise in self-delusion. If we were to continue to "improve" upon the analogy by considering the largest and most complex of man's inventions, namely his industrial society, which would be most like the universe in size and complexity, we discover that there is no overall design at all! It grew as the result of natural selection of many separate parts (i.e. laissez faire capitalism) much the way a natural community of organisms evolved. The creationists themselves, being a politically conservative lot, would consider any central planning of our society anathema—that's socialism and communism!
The argument from design is applied on a smaller scale to explain the patterns of structure found in living organisms by studies in comparative anatomy and physiology. Thus Morris says:
"On the assumption of creation, it is reasonable that there would be resemblances between creatures and that these resemblances would be stronger between those creatures living in similar environments and with similar physiological functions to fulfill. One could hardly imagine any more probable an arrangement than now prevails if the origin of all things actually were special creation."
Evolution And The Modern Christian, P. 23.
If Morris stands by this statement then creationism is falsified, because this is not what is found in nature! The classic example of the vertebrate limb will illustrate what I mean. The mole lives in the soil and uses its legs for digging. The horse lives on the plains and uses its legs for running. The ape lives in the trees and uses its limbs for climbing and brachiation. The whale lives in the sea and uses its limbs for swimming. The bat flies through the air using its limbs for wings. What we have here is a group of mammals, living in different habitats and using their limbs for different functions, yet these limbs are all constructed on the same "plan" with the same bones and muscles.
An even more remarkable example concerns the mouthparts of insects, the great variety of which are all formed by modification of the same set of basic parts (which in turn are modifications through evolution of three pairs of legs). The chewing mouthparts of many insects function like a meat grinder; the sucking mouthparts of a mosquito or bug are constructed and function amazingly like a hypodermic syringe while those of a housefly are similar to a vacuum cleaner. Yet what engineer would attempt to design a meat grinder, a hypodermic syringe and a vacuum cleaner from the same set of parts? or a shovel, an automobile wheel, a boat propeller and an airplane wing from the same set of parts?
Organisms that do live in the same habitat and whose structures perform the same functions are often very unlike! Consider the mole and the earthworm, the horse and the grasshopper, the ape and the tree snake, the whale and the squid, the bat and the moth, etc. When we do find organisms with similar structures performing similar functions, we call it parallel evolution if the organisms are closely related and convergent evolution if they are distantly related. Convergent evolution results when the basic physical requirements for a particular function are very narrow or even unique. Thus there seems to be essentially one shape for large objects moving rapidly through water, a shape exemplified by sharks, ichthyosaurs and dolphins, yet even here those similar external shapes conceal widely divergent anatomical structures underneath.
Clearly the "design" of organisms as revealed by comparative studies is incredibly conservative ("niggard in invention, prodigal in variety" as Darwin put it) even to the point of irrationality. This is exactly what you expect of natural selection but no human designer (the only intelligent designers that we actually know exist) would ever think of doing things this way! If organisms were made by a Creator as creationists claim, then that creator functions in a manner totally alien to any intelligent designers we know of.
There is nothing in the manmade world of macroscopic contrivances, essentially mechanical and electrical, that is remotely analogous to the chemical interactions of atoms and molecules upon which the organization of living organisms is based. It's not the Second Law of Thermodynamics that prevents the parts in a junkyard from spontaneously assembling themselves into an automobile. First, these parts have no means of locomotion and are pinned to where they lay by the force of gravity, and second, even if a tornado flung them around, they are incapable of interacting with one another if they should collide. On the other hand, atoms and molecules are in motion and they do react with one another when they collide! Consider that if General Motors made cars the way DuPont makes chemicals, the parts for a car would be dumped into a big vat and stirred, whereupon they would react with each other and automatically assemble themselves into a car.
In nature, organic or inorganic matter is normally found in complex chemical forms. In fact, the main task of our basic industry is to break down chemically complicated ores to produce the relative simple pure metallic elements from which our technology is fabricated. When one considers the field of geochemistry, there is overwhelming evidence for the production of highly complex organizations by natural means. One doesn't normally describe the complex chemical structures of clay minerals to the direct activity of some higher intelligence but to the natural physical and chemical processes of erosion and weathering.
If I found the bones of a cow, I would not deduce the existence of a cow designer. There is a great deal of observational evidence that cows (and all other organisms) reproduce themselves and that cow embryos grow and develop without the supervision of a "cow designer"—another obvious and fundamental difference between organisms and human artifacts. This is even more remarkable when you realize that in sexual reproduction (practiced by virtually all eukaryote organisms), the somewhat different instructions from two individuals are "cut up" into pieces and reassembled at random into a new, different third set of instructions, that much more often than not, functions to produce a new unique individual. Try that with the plans for two different models of autos, or two different versions of a computer program!
In the manufacture of an automobile, all the parts are fabricated separately, often in different factories, and they do not come in contact until they meet on the assemble line. The only reason that they fit together at that time is that they were all fabricated to the specifications of a master set of plans. And if they don't fit (maybe the wrong size parts were shipped) there is nothing that can be done about it. Organisms, however, grow and develop from zygotes in a fundamentally different way. All the parts form together in situ in the zygote and interact with one another as they develop! This allows the new composite set of instructions produced by the process of genetic recombination characteristic of sexual reproduction to successfully produce a new unique individual. The closest analogy to this is the cutting up of a picture painted on a piece of wood to make a jigsaw puzzle. The contours of the two pieces on either side of a cut, even if it is done randomly, are automatically complementary and will fit when they are put together again.
The authors of Pandas (Davis, P. and D. H. Kenyon, 1989. Of Pandas and People. Haughton) claim that "similarities among living things are like pre-assembled units that can be plugged into a complex electronic circuit." Yet the modifications to the basic plan exhibit much variety. An almost ideal example of a "pre-assembled unit" would be an enzyme like cytochrome c. One would expect it to be identical in all living things, yet it isn't; it exhibits a wide variation in amino acid composition despite its identical function under identical chemical conditions in virtually all forms.
The nineteenth century morphologists ascribed the basic plan of the vertebrates to a philosophical, ideal Archetype. The Pandas' authors claim the intelligent designer is forced to work with a limited vocabulary of possible forms. But wait, there is more than one Archetype! In fact, there is probably one for every phylum. Arthropods have heads, bodies, legs and systems (skeletal, muscular, nervous, circulatory, digestive, excretory, etc.) analogous to vertebrates but built along entirely different lines. Arthropods are about as different from vertebrates as one can imagine two organisms to be! No one company in the human world would make similar products that are so thoroughly and radically different. One can only assume that a different designer (or design team) using a different set of forms, was responsible for the arthropods. It follows that there must be such a team for each of the phyla!
The Pandas' authors say we must take the fossil record at face value. If new organisms appear suddenly in the record it is because designers were making new forms throughout geologic history. For example, since the early Mesozoic, designers had produced pterosaurs, specialized flying forms, that apparently did very well. In the late Jurassic period, another designer, the inventor of the feather, thought it could accomplish the same end by simply putting feathers on a theropod. The result, Archaeopteryx, apparently didn't work too well and its production was cancelled. Later, the designer and possibly its colleagues, decided that they could make it fly if they got rid of the bony tail, replaced the toothed jaws with a beak, completely revamped the skeleton, the flight muscles, and the respiratory system (probably getting some of their ideas from the pterosaur designers.) They ended up with a very efficient flying machine that apparently put the pterosaurs out of business. Still later, for some mysterious reason, they crippled a lot of these birds making them flightless (penguins, auks, rails, ground pigeons, kiwis, tinamous, some cormorants, emus, ostriches, moas, etc.). Now what aircraft company would take a good airplane, remove its wings and try to market it as an auto?
Taking the fossil record at face value also means that if a form is not found in the fossil record, it never existed! It follows that the designers, for some reason, were continually wiping out their creations. They wiped out the coelacanths at the end of the Mesozoic, then reintroduced one for the present day! The fossil record of insects is very spotty. The arthropod designers, unable to make up their minds?—must have wiped out and remade the insect orders up to a dozen times!
The Pandas' authors suggest that all the biochemical similarities of organisms serve to make the food chain efficient! But why have a food chain? There is nothing comparable among human design products. And you can have a viable ecosystem with just microorganisms. Multicellular animals and plants are superfluous. The adaptations of predators and prey are like an arms race among weapons manufacturers. But the designers of a counter-weapon are not the same designers that designed the weapon. They usually work for a different company and a different nation. There is obviously an intense rivalry among the biological designers, given the fantastic array of predators and parasites and the strategies, bordering on the fiendish and diabolical, that they use to catch and eat their prey! More than half the known species of animals are parasites on other living animals. Some of these design rivalries are bizarre. Even Darwin couldn't imagine an intelligent designer designing tens of thousands of species of insect parasitoids, that eat their living hosts from the inside.
The Pandas' authors argue that organisms contain information and the only known way to produce information is to be produced by intelligent designers. Actually this is an arbitrary and religiously-biased conclusion. Organisms contain information and as we have already mentioned, they reproduce themselves and that information in a fundamentally different way from human-generated information. Thus observation suggests that there may be another way to generate information. After all, we have never seen an intelligently designed organism pop into existence-although for many centuries people thought that was a common occurrence. They called it spontaneous generation!
The evolutionary mechanism of mutation, sexual recombination, reproduction and natural selection has been shown to work. The "design patterns" displayed by the biotic world and the known fossil trends are all what one would expect from evolution guided by natural selection. Even DNA, the information storage material is full of silent, noncoding nonsense sequences. In a recent article entitled Natural Selection for Computers which appeared in Science News (Nov. 25, 1989; vol. 136(22): 346-348) Ivars Peterson reports on the technique of "genetic algorithms" to design jet engines, integrated circuit chips, scheduling work in a busy machine shop, operating gas-pipeline pumping stations and recognizing patterns. The technique, pioneered by computer scientist John H. Holland at the University of Michigan, simulates the mechanism of Darwinian evolution, involving mating, genetic recombination, reproduction, selection and even mutation. Here are engineers (no less!) using Evolution To Design things. Maybe the Pandas' authors can be persuaded to accept theistic evolution!
Science is an activity by which man seeks to understand the universe, i.e. all the observed phenomena. Scientists do this by making generalizations (or laws) about the phenomena and providing explanations (or theories) about the generalizations. That science seeks laws and theories implies two assumptions about the universe: (a) it is consistent in time and space—otherwise generalizations would be impossible and (b) it is understandable—otherwise theories would be impossible. These two assumptions are themselves testable hypotheses. A third assumption that it is important to state is (c) the observed phenomena accurately reflect the underlying reality of the universe (the true nature of things.)
The key to the success of science is that it subjects its ideas to empirical tests. The basis of the testing process is diagrammed in figure 1. Observed phenomena are what we detect; they are produced by the underlying true nature of things which we seek to discover. Because these "true natures" are not directly observable, our hypotheses about them cannot be tested by direct observation. Thus one deduces observable logical consequences (the predicted phenomena) which may be compared with observations.
If the consequences do not match the observations, then the hypothesis does not match the true nature of things and we say that the hypothesis has been falsified. If they do match, we cannot be sure that the hypothesis matches the true nature of things, for experience has shown us that several hypotheses may equally well explain a set of phenomena and we may have to look further to distinguish them. Also further investigations may reveal new phenomena that falsify a previously accepted hypothesis. Thus an hypothesis may be disproved or falsified, but never proved.
The temporal sequence of this activity is illustrated in figure 2. There is a problem to be solved. One guesses at the answer—the hypothesis—and deduces the observable consequences which are then compared with new observations. (It is most desirable that the hypothesis have consequences for an array of phenomena that were not considered in its original formulation. This independence of testing from the original basis is important to avoid confirming the hypothesis by circular arguments.) The hypothesis may be rejected, accepted or modified. As we go around this cycle of intellectual activity, we hopefully come closer and closer to the truth—defined by the philosopher Karl Popper as correspondence of the consequences with the observations.
A law is the assertion of an invariable association (not necessarily sequential or causal) of observations. It can be tested by direct measurements on the relevant phenomena. A theory is an explanation of laws (i.e. expresses them in a more acceptable and satisfactory form—more satisfactory because the form is more familiar and/or general.) Almost always, some of the ideas in a theory cannot be tested by direct perception (an important distinction from laws!) A theory may postulate entities or processes too small to be observed (atoms, electrons, etc.), intrinsically invisible (electromagnetic fields, curved space, black holes, etc.), too far distant (stars, etc.), inaccessible to observations (the interior of the earth, sun, etc.) or remote in time (evolution.)
From the above discussion we see that scientific hypotheses must be testable (falsifiable). Because the goal of science is understanding, they should also be informative, providing the how, where, when and why a phenomenon occurs and what it is or what causes it. The more informative a hypothesis, the more specific the logical consequences and the greater is the potential for falsifiability. It is also preferred that a given hypothesis cover as wide a range of phenomena as possible (Whewell's consilience) with the fewest assumptions or the simplest possible mechanism (i.e. the principle of Occam's razor). Generating the most logical consequences is important, because the testing of these constitutes a guide for future research, pointing out what facets of nature should be investigated next. This role is so important that Popper advises that an apparently falsified hypothesis should not be discarded until all of its logical consequences have been explored. This insures that we will have the maximum knowledge necessary upon which to base a new hypothesis. Thus fruitful hypotheses can make important contributions to scientific knowledge even if they eventually turn out to be false! Whewell considered consilience the definitive evidence for the truth of a theory.
By now it should be clear that vitalistic and supernatural hypotheses that invariably postulate vague and amorphous mechanisms whose workings are beyond human comprehension are untestable and uninformative and hence not scientific. In fact they are not even explanations, but statements of unsolvable mysteries beyond the powers of scientific investigation.
Actual testing is more complex than we have described (see figure 3) because any general hypothesis (law or theory) can only entail general consequences. But it can only be tested against specific instances of real systems. Thus we need a set of initial or specific conditions of the system under test. Combined with the general postulates, they constitute a model—an abstract representation of some natural or artificial system whose predicted behavior is compared with the real system.
Several important points can be made here:
In carrying out such a test, we are testing several things at the same time: (1) the general law or theory, (2) the correctness of the specific conditions, (3) the deductive processes leading to the consequences and (4) the accuracy of the observations. Difficulties with any of these can lead to apparent falsification. Thus it is said that when Newton was first testing his gravitational hypothesis using the specific instance of the moon's orbit in 1665, the calculations did not agree with the observations because, as it turned out, he was using an incorrect value for the moon's distance. In recent attempts to improve upon the orbital parameters of the planet Neptune, possible inaccuracies in early observations of the planet and in the specific conditions, including the possible perturbations of a tenth planet (other than Pluto) had to be considered. In piecing together the evolutionary history of a particular organism, say man, each new fossil adds new observational details to be considered by the specific conditions. Here the specific conditions constitute what Philip Kitcher calls a "Darwinian history" or "evolutionary scenario" accounting for the known facts about fossil and recent men.
We can't test every relevant instance—only those for which we have sufficient knowledge of the specific conditions. If, for example, we have only one observation on a newly discovered asteroid, we cannot compute its specific elliptical orbit and thus its future positions in order to test Kepler's and Newton's laws. Likewise, without specific fossil evidence, we can only speculate on the evolutionary pathways leading to such oddities as the archerfish and the platypus.
The observable logical consequences are often called predictions and creationists often point out that evolutionists cannot predict the evolutionary future, thus evolution is not testable. But these consequences are necessarily predictions only in the broad sense that they predict the results of observations yet to be made. They are not necessarily predictions of the future state of some natural system. In fact, most scientific "predictions" are conditional: given the relevant initial conditions, usually of some artificial system (such as a mixture of chemicals in a test tube) the immediate future state can be predicted. It is different with a natural system which is usually very complex and where most of the specific conditions are not under our control or are unknown. Only in the very special cases where the system is fairly isolated and repetitive (such as the movements of the bodies of the solar system and phenomena related to them like the seasonal climatic patterns; or the life cycles of organisms) can we normally make successful predictions of the future. (Consider the success of the weatherman in predicting the immediate future weather!) Thus the inability of Darwinism to predict the future evolution of species does not set it apart from other scientific hypotheses or theories.
Finally, once general laws and theories are established by testing them against specific instances of phenomena, the explaining of other specific instances consists of determining or hypothesizing the appropriate specific conditions. This is true in physics and chemistry and is especially true of the applied sciences. And the historical sciences may work exclusively in this mode. They include hypotheses about unique, past events which to be testable, must have observable consequences for the present. Here the emphasis in the testing procedure is shifted from the general laws to the specific conditions; the general laws and theories are taken for granted and the specific conditions are tested.
What about repeatability in the historical sciences? It is the observations that must be repeatable, if only to establish their validity independently of any one person's authority. This does not mean that the hypothetical mechanism or the phenomena concerned must be repeatable or reproducible. In the experimental lab where the phenomena being studied are short-lived and transient, it is usually necessary to reproduce them in order to repeat the observations. But scientists must wait for the reoccurrence of natural phenomena, such as eclipses, earthquakes, seasonal biological phenomena, etc. Yet if a phenomenon is a stable, more or less permanent long-time condition, observations may be repeated anytime. A geologist may return to a geological formation to repeat or make new observations. An anatomist or paleontologist may reexamine a museum specimen, either corroborating or refuting someone else's previous observations.
In figure 4 I have listed a number of the general consequences of the Darwinian mechanism and they constitute a fairly rigorous set of requirements which present ample opportunities for falsification. Yet in every case where there is sufficient knowledge of the specific conditions—in the form of fossil evidence—the facts are in correspondence with these general predicted features. An example:
In the late 19th century, on the basis of evidence from comparative anatomy and embryology, it was hypothesized that mammals evolved from reptiles. This was independently tested (and confirmed) by the discovery of the mammal-like reptiles. Because of the relative abundance of the fossil evidence, the South African paleontologist Broom, on the assumption of natural selection, in 1912 predicted the nature of the necessary transition forms in the evolution of the mammalian jaw joint from the reptilian condition (figure 5). This included a phase where a double jaw joint, the reptilian and the mammalian ones together, occurred. It was almost 50 years later before the predicted fossils represented by Diarthrognathus and Morganucodon were actually found! This forecast of the kind of fossil that should be found is an example of the observable logical consequences possible in evolutionary theory and characteristic of science.
The oft-made distinction between the "hard" sciences (physics and chemistry) versus the "soft" sciences (biology, etc.) is based on the fact that the hard sciences have produced "universal" laws and theories admitting of no exceptions in contrast to the generalizations of the soft sciences which many authorities are even reluctant to call laws. This is often explained as a result of the hard sciences being older and more "mature" and possibly some day, ecology, for example, may produce universal laws of its own. The difference between hard and soft science, however, stems from the nature of the systems the various branches of science deal with. Physics (especially, and chemistry to some extent) restrict themselves to the simplest unvarying universal systems. Hydrogen atoms are universal and virtually identical, the variations being limited and reversible. Contrast this to a sexually-reproducing species, where virtually every individual, past and present, is unique in a great many ways; or an ecosystem, no two of which are the same. Thus, because of the nature of the subject matter, the life sciences, etc. will always produce generalizations of limited applicability and many exceptions. (Actually whenever a physicist studies a complex physical system it is separated from physics into a science of its own, such as geology and all its branches, meteorology, fluid dynamics, astrophysics, planetology, etc., all of which have features of "soft" science.)
The pioneers of science—Copernicus, Kepler and Galileo—were all neoplatonists or neopythagoreans and these influences guided them in proposing mathematical hypotheses. The tremendous success of these initial researches—culminating in Newton—set off the activity of scientists and philosophers in search of mathematical laws and explanations involving the motions of particles and the properties of fields that continues to the present day.
The interpretation of a chance event as one occurring in the absence of any antecedent causes is used only in some aspects of quantum physics. Otherwise a chance event or factor is one having a multiple of causes or initial conditions, most or all of which are unknown, usually for practical reasons. A large series of such events may exhibit a pattern and a probability of occurrence described by statistical laws (binomial, normal distributions, etc.)
Random has two meanings: (1) alternate outcomes of a type of event have equal probabilities of occurrence. Thus a random sample is one chosen in such a way that every individual in the population had an equal chance of being included in the sample. (2) Different events are independent, i.e. the causal chains leading up to several events have no links in common. Thus the occurrence of mutations are random with respect to the adaptiveness of the resulting phenotypes. A deterministic model explains a phenomenon or describes a system completely in terms of definitely known causes. A stochastic model includes chance factors obeying certain stated statistical laws.
There is usually a degree of inaccuracy or uncertainty and irreproducabilty in observations. Counts (ex: the number of eggs in a bird's nest) may be accurate but measurements (ex: the weight of a mouse) are usually approximate to some degree because of the limitations of the measurement device and/or procedure. Repeated observations of the same phenomenon may also display variation because each observation is the result of many factors, some of which may be beyond the control of the investigator and some of which may even be unknown. This is especially true with the complex systems of the "soft" sciences such as biology where each individual organism is unique in many ways. Thus there always appears to be a chance component to such observations.
When quantitative phenomena are being investigated, statistical methods allow the investigator to analyse observational data taking into consideration the chance components associated with the data. It is usually assumed that the chance elements are random in some fundamental way. The variation in observations may be summarized by descriptive statistics, deductions may involve mathematics and probability theory while the testing (falsification) procedure will involve experimental design and statistical hypothesis testing.
Aulie, R. P. 1975. The Origin of the Idea of the Mammal-like Reptile. III. The Mammal-like Reptiles. Amer. Biol. Teacher. 37(1): 21-32. (Jan.), (See esp. pp. 25-27 for jaw transition hypothesis.)
Baker, J. J. W. and G. E. Allen. 1968. Hypothesis, Prediction and Implication in Biology. Addison-Wesley.
Bronowski, J. 1960. The Common Sense of Science. Pelican Books A507. 1973. The Ascent of Man. Little, Brown and Co.
Burtt, E. A. 1932. The Metaphysical Foundations of Modern Science. Doubleday Anchor Book A41.
Campbell, N. 1952. What is Science? Dover Pub. Co. (Distinction between law and theory.)
Crombie, A. C. 1959. Medieval and Early Modern Science (2 vols.) Doubleday Anchor Books A167a, b.
Gardner, M. 1969. Mathematical Games (Simplicity as a scientific concept: Does Nature keep her accounts on a thumbnail?) Sci. Amer. 221(2): 118-121 (Aug.) 1976. Mathematical Games (On the fabric of inductive logic, and some probability paradoxes) Sci. Amer. 234:(3): 119-122 (Mar.)
Kitcher, P. 1982. Abusing Science. M.I.T. Press. (See esp. pp. 50-53, 69 for "Darwinian histories.")
Naylor, B. G. and P. Handford. 1985. In Defense of Darwin's Theory. Bioscience 35(8): 478-484. (Sept.)
Popper, K. R. 1957. The Poverty of Historicism. Boston. The Beacon Press (See esp. pp. 106, 143-147 for the historical sciences, pp. 122-124 for specific conditions, pp. 131-134 for testing and prediction.) 1959. The Logic of Scientific Discovery. Basic Books, Inc. N. Y. 1963. Conjectures and Refutations: the Growth of Scientific Knowledge. London. Routledge and Kegan Paul. (See esp. pp. 339 fol. for conditional predictions.) 1963a. Science, Problems, Aims, Responsibilities. Federation Proceedings. 224: 961-972 (July/Aug.), (An authoritative summary of Popper's views.) 1972. Objective Knowledge. An Evolutionary Approach. Oxford. Clarendon Press. (See esp. pp. 44 for truth, 355 for independence of testing.)
Ruse, M. 1979. The Darwinian Revolution. Univ. of Chicago Press. (See esp. pp. 58-59, 179-180, 279 bottom, for consilience.)
Salmon, W. C. 1973. Confirmation. Sci. Amer. 228(5): 75-83 (May).
Sokal, R. R. and F. J. Rohlf. 1981. Biometry. 2nd Ed. Freeman. San Francisco.
Stent, G. S. 1972. Prematurity and uniqueness in scientific discovery. Sci. Amer. 227(6): 84-93. (Dec.)
Article on Newton, Encyclopaedia Brittanica. 1946. 16: 362C.
Galilean Satellite; In Science and the Citizen. Scientific American 243(3): 90-92. (Sept. 1980); Did Galileo see Neptune? Science News 118(15): 231. (Oct. 11, 1980); What's bothering Neptune? Science News 119(5): 68. (Jan. 31, 1981).
The above account of Science is based in part on a paper "The Evolution/Creation Controversy and the Nature of Science" presented by F. J. Sonleitner at an Iowa Academy of Science Symposium, April 23, 1983, at Luther College, Decorah, Iowa.
The skeletal organization of certain crossopterygian fishes and that of early amphibians was extremely similar, the main difference being in the limbs. Ichthyostega is an intermediate form in every way—skull, axial skeleton, pectoral and pelvic girdles, the flipper-like hind leg. It also had fish scales, a fishlike caudal fin on its tail, a lateral line system, and an operculum or gill cover, presumably covering sets of gills. This and several related fossils are described by the paleontologist Jarvik as "four-footed" fishes.
If one objects that Ichthyostega already had "feet," it should be pointed out that the lobe-fin of the crossopterygian fish is already half-fin, half-foot. It has all the structures of the leg itself. It only needs reorganization of the peripheral elements into toes and a reorientation or rotation of the limb so the "feet" point forward.
The modern day Latimeria swims with a motion of the paired fins that resembles a trotting gait, that is, the front right fin works in tandem with the left rear and vica versa. The front fins are quite flexible and can be rotated 180 degrees.
Diagrams are from:
Schmalhausen, I. I. 1968. The Origin of Terrestrial Vertebrates. Academic Press. pp. 36, 55, 59 and 61.
See also: Jarvik, E. 1955. The Oldest Tetrapods and Their Forerunners. Scientific Monthly 80(3): 141-154.
Fricke, H. 1988. Coelacanths: The Fish that Time Forgot. National Geographic, 173:824-838. (June) for the swimming of Latimeria.
Overall, the skeleton is typical of many small- sized Pseudosuchian and Coelurosaurian reptiles (ex: Compsognathus) and quite different from that of the pigeon whose body skeleton show extensive fusion and reinforcement of parts forming a strong boxlike "fuselage" with a great keeled sternum, a lightweight skull and toothless beak.
The only reason Archaeopteryx was not classified as a dinosaur is because it had feathers. It was probably a climber, glider or weak flier.
Heilmann, The Origin of Birds, pp. 33, 166.
The reptile-mammal transition is the most thoroughly documented vertebrate transition series and includes hundreds of species of the Reptilian Subclass Synapsida (the mammal-like reptiles)! What do the creationists say about it?
The fossil record throws very little light on the hypothetical evolution of amphibians into reptiles, or that of reptiles into mammals. All of them are four-legged vertebrates with similar skeletal structures and thus their fossilized remains provide little basis for distinguishing between them. Among animals living today, there are certain reptiles whose bony parts closely resemble those of certain amphibians and others that closely resemble certain mammals. The external characters and appearance, as well as the physiological functions, of amphibians, reptiles and mammals, are all vastly different from each other, but these differences need not show up in the fossil record.
The fact that it may be difficult to tell, for example, whether a certain fossil was a reptile or a mammal does not mean at all that it was transitional between the two in an evolutionary sense. If we could see the whole animal, and not just its skeleton, it would quickly be apparent which it was.
Of much more significance is the fact that each of the various orders of amphibians, reptiles and mammals appears suddenly in the fossil record, without incipient forms leading up to it and without transitional forms between it and any other order."
Morris, H. M. 1974. Scientific Creationism, p. 83-84.
Again Morris manages to get almost everything wrong! The fossil record throws much light on the actual transitions between these three classes, especially the reptile-mammal transition. Although they are all four-legged animals, there is no difficulty in distinguishing the fossil remains of the three classes, except for certain forms: the Semouriomorphs have a mixture of amphibian and reptilian skeletal characters and were first classified as reptiles, but more recently as amphibians when related taxa were found to have larval stages with external gills; and the cynodonts, many of which are so like the earliest forms classified as mammals that their classification as reptiles or mammals is arbitrary. Among living forms amphibian, reptile and mammal skeletons are all distincty different from one another.
Morris discounts the transitional forms by saying that if we could see the whole animal, we could quickly tell what it was. Now in the evolution of mammals from reptiles, not all the mammalian characters evolved simultaneously. Some were acquired earlier than others. For instance all mammals have hair, nurse their young and can regulate their body temperature by physiological means, thought not all can do the latter equally well. But the monotremes still have a totally reptilian mode of reproduction, and that of the marsupials is intermediate between the reptilian and the placental condition—their embryos have a vestigial egg-tooth and for the first two-thirds of pregnancy are encased in a thin shell and shell membranes. On the other hand, there is evidence that the cynodont reptiles had hair and were endothermic (warm-blooded). The Monotremes (the living platypus and echidna) have such a combination of mammalian and reptilian characters that at least one authority states that it makes more sense to classify them as living mammal-like reptiles. (Another says the advanced synapsids (therapsids) should be classified as reptile-like mammals.) Thus it seems likely that if we could see the whole animal, we might be more likely to mistake a furry cynodont for a mammal!
"The two most easily distinguishable osteological differences between reptiles and mammals, however, have never been bridged by transitional series. . .In some fossil reptiles the number and size of the bones of the lower jaw are reduced compared to living reptiles. Every reptile, living or fossil, however, has at least four bones in the lower jaw and only one auditory ossicle, the stapes.
There are no transitional forms showing, for instance, three or two jaw bones, or two ear bones. No one has explained yet, for that matter, how the transitional form would have managed to chew while his jaw was being unhinged and rearticulated, or how he would hear while dragging two of his jaw bones up into his ear."
Gish, D. T. 1972. Evolution The Fossils Say NO!. Creation-Life Pub. p. 58.
Reptiles have 7 bones in lower jaw. In mammal-like reptiles progressive reduction occurred in all of these but the dentary and articular. In the latest cynodonts, The dentary is the functional lower jaw, but the articular is still present as the jaw joint. The angular is present with a crescent shaped projection supporting the tympanum. The remaining 5 bones are reduced to tiny slivers forming a rod in a groove on the inner side of the dentary. The fossil Morganucodon, classified as a mammal, has a similar jaw except that the dentary has also established contact with the squamosal bone, so that the typical mammalian jaw joint is also present. Morganucodon and several related genera in the mammalian order Docodonta retain the reptilian lower jaw and form the new subclass Eotheria. We can't say for sure how many other of the early Mesozoic mammals had reptilian-like lower jaws because most of them are known only from teeth. Present day mammals have only one bone in the lower jaw, the dentary, but the articular is present as the malleus, the angular as the tympanic and the prearticular as the anterior process of the malleus. Thus Gish's imagined transitional series was not how it happened. Three of the original seven jaw bones disappeared; the three associated with the ear, along with the quadrate, moved to the head as a unit, leaving the dentary. The jaw never had to be unhinged and rearticulated. Broom described and predicted the actual jaw-joint transition forms in 1912 and Watson described them at length in a 1951 book. That Gish is apparently unaware of this literature documents his ignorance, not any unsolved problem of mammalian origins.
The earliest synapsids (Pelycosaurs) from the Upper Carboniferous and Permian were reptile-like. Later forms acquired incisor and canine teeth for stabbing and cutting up prey. The later synapsids (therapsids) in the Triassic acquired premolar and molar teeth, expansion of the dentary bone eventually forming a dentary-squamosal (mammalian) jaw joint in the latest forms, mammal-like skull and jaw muscle arrangements and secondary palate for chewing. Concomitant with these was a change from the reptilian alternate tooth replacement to diphylodonty (single replacement of milk teeth by permanent incisor, canines and premolars with molars added consecutively from front to back.) The post-cranial (body) skeleton also illustrates acquisition of mammalian traits associated with more efficient locomotion. All these changes first appear as minor modifications of reptilian anatomy and gradually over time became better expressed and more pronounced.
On the basis of various lines of evidence (geographic location in the higher latitudes of the Permian and Triasic world, their high predator/prey community ratios, their bone histology, indications on the skulls of pits for whiskers (and hence hair), grooves and depressions for sweat glands moistening the nose, presence of mammalian ethmoid turbinal bones, the absence of ribs in the lumbar region possibly indicating the presence of a diaphram) it is suggested that therapsids were endothermic and hairy. The more advanced ones may have nursed their young.
Hearing is often associated with the lower jaw in reptiles. In the modern lizard, part of the tympanic membrane is attached to a backward projection of the lower jaw, so that chewing affects hearing. Snakes have no tympanum yet they can hear by vibrations picked up and conducted by the jawbones. The earliest synapsids (which were not very mammal-like) also lacked of a tympanum. This was lost due to a reorganization of the back of the skull which occurred in the stem reptile (Cotylosaur) ancestors of the synapsids and obliterated the otic notch. In later synapsids, the angular bone developed a crescentric posterior margin which apparently bore a tympanum on the side of the lower jaw. This tympanum was also in contact with the articular and sounds were transmitted via the articular, quadrate and stapes to the inner ear. When the mammalian jaw-joint was formed next to the reptilian one, those bones associated with hearing became very small and migrated (along with the tympanum) off the jaw onto the head.
If you think that it is ridiculous that a reptile might have an eardrum on its lower jaw and that the jaw joint was involved in hearing, consider that living amphisbaenid lizards hear with a flap of skin on the lower jaw which communicates with the inner ear by a long cartilaginous extension of the stapes that crosses the jaw joint!
If you doubt the evidence of comparative anatomy involving the mammalian auditory ossicles, their associated muscles and innervation and blood vessels that identifies them with reptilian jaw elements, consider their embryological development. In all mammals they first form in conjunction with the lower jaw and only later move into the ear region. The newborn marsupial, which is hardly more than an embryo but which needs functional jaws to fasten to the nipple in the pouch, has a functional reptilian jaw joint (quadrate and articular)! Only after the dentary bone grows and contacts the squamosal bone of the skull forming the mammalian jaw joint, do the quadrate and articular move into the ear and take up the functions of incus and malleus, respectively. Prior to this functional shift, the embryonic jaw bones closely resemble those of a mammal-like reptile.
What the creationists must explain is: (1) why the Creator made a complete series of "transitional" forms between the reptiles and mammals and (2) how the great cataclysmic, chaotic, destructive Flood managed to sort out and deposit these forms in a perfect depositional time sequence in such beds as the Karroo formation in South Africa. Isn't it paradoxical that the creationists insist that order cannot come from chaos, yet that's exactly what they expect us to believe when they claim that the Flood produced such varied and often finely-structured sediments containing "evolutionary" sequences of all forms of organisms? Finally, to explain the embryological evidence, we might require them to explain why mammals and man are produced by developmental systems derived and modified from reptilian ones? If man is made in the Creator's image surely he ought to have a unique developmental system. Possibly that of the mammals and reptiles might be derived from man's by a lazy creator lacking in originality, and by a stretch(!) of the imagination, we might conceive that the mammalian earbones might move into the reptile jaw to become jaw elements, but the reverse?
Aulie, R. P. 1974. The origin of the idea of the mammal-like reptile. American Biology Teacher. 36(11): 476; 36(12);545; 1975. 37(1): 21. (A good general account; describes Broom's predications about the jaw joint transition.)
Bakker, R. T. 1975. Dinosaur renaissance. Scientific American 232(4): 58-78 (April). (Evidence for endothermy in Triassic mammal-like reptiles.)
Brink, A. A. 1956. Speculations on some advanced mammalian characteristics in the higher mammal-like reptiles. Palaeontologia Africana, IV: 77-95. (Evidence for hair, sweat glands, single replacement dentition, possibly nursing.)
Cain, J. A. 1988. Creation and mammal origins. Journal of Geological Education 36(2): 94-105. (A good general account; answers Gish's "creative quotations" and other inaccurate comments about the subject.)
Carter, G. S. 1967. Structure and habit in vertebrate evolution. Univ. of Washington Press. (See chapter XVII for the characters of the Monotremata.)
Crompton, A. W. and Pamela Parker. 1978. Evolution of the mammalian masticatory apparatus. American Scientist 66(2): 192-201
Gans, C. and E. G. Wever. 1972. The Ear and hearing in Amphisbaenia (Reptilia). Journal of Experimental Zoology 179: 17-34.
Hopson, J. A. 1987. The mammal-like reptiles: A study of transitional fossils. American Biology Teacher 49(1): 16-27. (General review with illustrations and critique of Gish.)
Hotton, N., P. D. MacLean, J. J. Roth and E. C. Roth (Editors) 1986. The ecology and biology of mammal-like reptiles. Smithsonian Inst. Press. Washington and London. x + 326 pp. (21 papers on a variety of subjects.)
Kermack, D. M. and K. A. Kermack. 1984. The evolution of mammalian characters. London, Croom Helm. (General review with discussion of teeth, chewing, hearing and Mesozoic mammals.)
Kermack, K. A., F. Mussett and H. W. Rigney. 1973. The lower jaw of Morganucodon. Zoological Journal of the Linnean Society 53: 87-175 and 1981. The skull of Morganucodon. Ibid 71: 1-158.
Lillegraven, J. A., Z. Kielan-Jaworoska and W. A. Clemens (Editors). 1979. Mesozoic Mammals. The first two-thirds of mammalian history. Univ. of California Press. (See esp. chapter 3 on mammal origin and chapter 13 on reproduction.)
Macintyre, G. T. 1972 The trisulcate petrosal pattern of mammals. Evolutionary Biology 6: 275-303. (See p. 278 for suggestion that Monotremes are mammal-like reptiles.)
McLoughlin, J. C. 1980. Synapsida: A New Look into the Origin of Mammals. Viking Press. (See esp. the chapter: The Making of the Mammals)
Olson, E. C. 1958. The evolution of mammalian characters. Evolution 13: 344-353.
Watson, D. M. S. 1951. Paleontology and modern biology. Yale Univ. Press. (See esp. chapters 5 and 6. See p. 139 fol. for the lizard ear. A good book for paleontological methodology and examples of predictions about fossils on the basis of evolution and the observed fossil trends.)
In 1860, Darwin wrote to Asa Gray, "Embryology is to me by far the strongest single class of facts in favor of change of forms." (Gould, 1977, p. 70). The creationists apparently agree; they studiously avoid discussing this class of facts in any detail. What Darwin was referring to was a mountain of facts emmassed by the early comparative embryologists showing that early stages in organismal development are much more similar than the adult forms would indicate. These facts were generalized in the form of two major interpretations: von Baer's laws which described the development of various forms diverging from a common general starting point and recapitulation, in which early embryonic stages of "higher" forms represent stages of forms "lower" on the ladder of life or the chain of being. Both had originated in a creationist world, but could be given evolutionary interpretations. Darwin (1958, chapter 14; 1982, chapter 13) briefly discussed these views in addition to proposing an explanation of his own. Later the German zoologist Ernst Haeckel advanced an evolutionary interpretation of recapitulation. Because present day creationists so quickly point out that recapitulation has been disproved, it is interesting to point out that the notable 19th century geologist, Louis Agassiz, embraced and expanded a creationist doctrine of recapitulation!
Why should early stages of vertebrate embryos of all classes resemble each other? Certainly all start from a single-celled zygote and go through cleavage (division of the zygote into the many small cells forming the blaustua) and gastrulation (formation of a three-layered embryo from the single layered blastula). But the parallels even extend beyond gastrulation, neurulation (neural tube formation) and into the organogenesis stage. Thus even terrestrial vertebrate embryos develop notochords, pharyngeal pouches, clefts and arches; their hearts and circulatory systems are very fish-like and undergo radical transformations, mammals display the same highly modified gastrulation process occurring in the large-yolked reptile and bird eggs; they even develop large empty yolk sacs; human embryos go through a tailed stage, etc.
To understand why this must be so, it must be realized that what is inherited is information to produce a functioning developmental system that will transform a zygote into the fully developed organism. Evolution proceeds by making changes in the developmental system so that a modified organism is produced. Indeed the system accommodates change. It must. In sexual reproduction the offspring receives a mixture of information from both parents. The new genome is unique. Try this with automobile blueprints or parts of two versions of a computer program! Because of the sexual shuffling of instructions, the "manufacture" of an organism is fundamentally different from the manufacture of, say, an automobile. In our factories, parts are made in isolation. They first come together on an assembly line and fit because they were all made according to rigid specifications. The parts of an organism develop in situ, not in isolation, and constantly interact in a variety of ways to insure the production of a functional individual in spite of the mixing of "specifications" from unlike parents. Sex was invented early; virtually all eukaryote organisms have it. Thus all multicellular organisms possess developmental systems that are flexible to some extent.
The experimental investigation of developmental systems is technologically demanding; they are very complex and very tiny (the human zygote is about the size of a pinhead) and much of their operating mechanisms are at the molecular level. Thus even with the modern techniques of molecular biology, progress in understanding them is painfully slow. Although we have an idea of the basic principles involved, there are many details still to be discovered. The principles relevant to understanding the link between development and evolution are presented in a highly simplified fashion in Figure 1. All developing structures and organs have at least two functions: (1) the primary function of becoming the operating part of the adult and (2) the secondary function of interacting with the rest of the system for the purpose of integrating it as the organism develops.
The simplest multicellular organisms, such as certain sponges and the freshwater hydra, can be teased apart into their individual cells and, left to themselves, the cells reassociate themselves into an organism (Balinsky, 1970, p. 667) In some cases mixtures of the cells from two related species can even recognize their own species. This same property is retained by the cells of various embryonic organs in complex forms (ex: kidney cells of mice; Moscona, 1961). Much of the organization in more complex forms is controlled by the process of induction. One part initiates the development of adjacent parts. Thus the presence of the notochord, which underlies the developing nervous system, is necessary for the successful differentiation of brain from spinal cord. The eye cup, growing out from the brain, induces the skin epithelium above it to form a lens; the latter in turn induces the formation of the cornea; the retinal tissue of the eye cup induces the lens material closest to it to form the lens fibers. Sometimes there is reciprocal induction. The mammalian kidney derives from two different rudimentary tissues. When these tissues grow into contact, the nephrogenic cord induces the ureteric bud to form the collecting tubes and the latter induces the former to develop the secretory tubules (Sussman, 1960, p. 80 fol.; Karp and Berrill, 1981, p. 421; Balinsky, 1970, p. 453).
Thus 20th century experimental embryology has shown that, after the main morphogenetic movements have occurred and organ and structure differentiation sets in, the system is a complex network of interacting parts. In the more advanced stages the interactions become more local and eventually the embryonic mechanisms are replaced by the nervous and endocrine systems which take over the task of keeping the organism integrated although some direct interactions persist into adult life, such as the interaction of bones, muscles and tendons; their precise form is strongly dependent upon the tensions and pressures they experience through their interactions (Weiss, 1939, pp. 448-457; Haldane and Huxley, 1927, pp. 184-187).
Clearly it would be difficult to make successful random changes in earlier stages than in the later ones. Because of the web of interactions, genes activated earlier in development are more pleiotropic (having more multiple effects) than those activated later and hence more likely to do something detrimental. Thus most successful changes come at later stages. For similar reasons, "new" organs and structures arise as modifications of old ones and not as completely new additions. (A in Figure 1.) Thus wings evolved from modified forelimbs and not as projections from the back as in angels, fairies and the mythical Pegasus. The secondary, integrative functions are very hard to modify or replace wihout instantaneous extensive reorganization, thus modifications occur later in development or if a structure or organ is eliminated, like teeth in birds, turtles, anteaters, baleen whales, etc. the early stages will be retained in some sort of rudimentary or vestigial state (B in Figure 1). Others (C in Figure 1), whose anatomy still reflects a primary function now eliminated, may persist into the adult stage because of secondary adult functions.
One of the most amazing and interesting embryological phenomena in the vertebrate embryo concerns the pharyngeal gill clefts that characterize all chordates (Balinksy 1970, p. 521 fol.; Karp and Berrill, 1981, p. 421 fol.). In the invertebrate chordate (Tunicates and Amphioxus) they are part of a filter feeding apparatus. In the aquatic vertebrates they bear respiratory gills. They are formed by pharyngeal pouches growing outward that induce the formation of corresponding branchial grooves or clefts that grow inward to meet them. These two sets of structures cause the neural crest cells, migrating downward from the sides of the nerve cord to be channeled between them and form the gill bars and associated arch tissues. Several of the aortic arches so formed are incorporated into the circulatory system of terrestrial vertebrates; other tissues of the third and fourth pouches form the parathyroid and thymus glands. The hyoid skeleton and various cartilages of the larynx, trachea and thyroid are derived from arch material. Why would a Creator have these diverse structures all develop from a set of embryonic structures that develop further to form the pharyngeal gill slits in fishes and amphibian larvae? (Temporary slits do form in reptile and bird embryos and occasionally in mammals—that is, the thin membrane between pouch and groove becomes perforated but soon after closes again.) The evolutionary answer is that these organisms have necessary structures that evolved from precursors in their fish ancestors that were part of these pharyngeal structures; hence their entire elimination would be fatal to the organism.
Another bizarre example involves the growth of the main venous system. The lowest vertebrates have two main veins, the posterior cardinal veins extending backward from the heart. These appear in the embryo and grow to their adult condition in a direct manner. Mammals have a single such vein, the vena cava, which develops in anything but a straight-forward fashion. Reflecting the many evolutionary changes that occurred in the development of this venous system, including the formation of a renal portal system in fishes, its abandonment in tetrapods and the formation of adult kidneys from more posterior tubules of the basic nephric system in mammals, the venous system of the mammal starts out as paired cardinal veins, and only after a series of complicated replacements, the single vena cava develops as an amazing patchwork (Balinsky, 1970, p. 478 fol.; Arey, 1946, p. 350 fol.). If it were made by plumbers, it would be a bewildering complex of joints and branches. Surely an intelligent Creator could have planned better!
Some structures may have multiple primary functions. The yolk sac in reptiles, birds and mammals is an example. Vertebrate embryos produce ventral extensions of the developing gut to envelop the yolk so that it may be utilized for nourishment while the embryo is developing in the egg. Eggs with large amounts of yolk allow for longer incubation times and the organism hatches in a more advanced state of development. Those with small amounts of yolk hatch early either as free-living larvae that can feed themselves (ex: frog tadpoles) or are fed (by placental connections with the mother as in most mammals; from nipples in the mother's pouch in marsupials). Reptiles and birds produce large, yolky eggs and the embryos have large yolk sacs that grow and become vascularized precociously. One of the earliest sources of blood cells is in the developing yolk sac membrane. Mammals have virtually no yolk in their eggs, yet the embryo quickly produces a large empty yolk sac, clearly not to enclose yolk but to provide an early source of blood cells and in many forms to form a temporary early connection with the mother as a choriovitelline placenta until the slower growing allantois (which stores uric acid wastes in bird and reptile embryos) can establish the more permanent chorioallantoic placenta (Arey, 1946, p. 80 fol.).
The conservativeness of the early stages of development can shed light on homologies and phylogenetic relationships. This possibility, codified in Haeckel's biogenetic law, spurred the growth of comparative embryology by late 19th century embryologists investigating problems of phylogeny. For example, the sucking mouthparts of lice (Insecta: Order Anoplura) which comprise three sets of piercing and sucking stylets, are so different from the mouthparts of other insects that the homologies between the structures is not apparent. Yet when one examines the early development of a louse, it becomes apparent that the dorsal stylets form from the maxillary lobe, the ventral stylets form from the labial lobe and the intermediate stylets are the hypopharynx. The early development of certain arthropods show that the coxal glands correspond to tiny coelomic sacs and nephridial tubes of annelids; and that the book lungs of scorpions correspond to the book gills of the horseshoe crab that have withdrawn into the body. Wingless fleas have wingbuds in the pupal stage and arrangements of sclerotized plates on their thorax characteristic of winged insects. This is evidence that fleas are secondarily wingless, having evolved from winged ancestors. In contrast are the apterygote insects which are primarily wingless. They never show wingbuds and the pleural sclerites of their thorax are similar to those on the abdomen and to those of other wingless arthropods such as the Chilopoda (centipedes). The larval form of the ascidians (sea squirts) revealed that they were chordates, not molluscs, while the larval form of the crab parasite, Sacculina indicates that it is a form of barnacle. Similarly the Ammocoetes larva of the lamprey shows the relationship between the vertebrates and the cephalochordates (Amphioxus). And the pharyngeal gill structures of terrestrial vertebrates indicate their kin to the aquatic vertebrates.
The gradual divergence of development of descendant forms from that exhibited by forms still retaining ancestral features is not the only way that evolution can modify developmental systems. The timing of various processes may change. DeBeer (1940) and Gould (1977) discuss such heterochrony at length. An example of heterochrony is paedomorphosis, the retention of juvenile ancestral characters by later ontogenetic stages of descendents. This process is envoked to explain why humans resemble juvenile apes in many morphological features much more than they do adult apes (Gould, 1977). (The author Aldous Huxley was so fascinated by this idea that he turned it into a plot for a novel: After Many a Summer Dies the Swan. New York: Harper and Bros.) The reverse process, the accelerated appearance of ancestral characters into earlier ontogenetic stages of descendants, mimics recapitulation, as in the opposum embryo, where the articular and quadrate bones form a functional reptilian jawjoint so that the oppossum can attach to its mother's nipple, those two bones later transforming into the malleus and incus earbones when the mammalian dentary-squamosal jawjoint finally forms (Lillegraven et al, 1979, p. 265; Watson, 1951, p. 156).
The fully functioning wing of adult insects contains little living material, hence these adults cease growing and molting. Thus the life cycle includes flightless, juvenile growth stages and the flying adult dispersal and reproductive stage. In the holometabolous insects (those with complete metamorphosis) these two main stages have diverged greatly both in ecology and morphology and the developmental system has virtually split into two. This is most evident in the flies (Diptera) and butterflies and moths (Lepidoptera). The caterpillar contains within it little islands of undifferentiated cells, the imaginal disks. In the pupal stage, most of the larval tissues are destroyed and the adult butterfly grows from these imaginal disks. Other insect orders exhibit this double developmental system to varying lesser degrees or not at all. (Saunders, 1982, p. 401 fol.).
Creationists attempt to explain away this embryological evidence by saying that recapitulation has been disproven (Morris, 1974, p. 77; Kofahl, 1980, p. 103). The fact that a hypothetical explanation of these embryological phenomena has been found wanting does not means that the phenomena do not exist. The phenomena do exist, and the evolutionary explanation based on the findings of experimental embryology as outlined above was proposed early in this century (Needham, 1930) and is accepted by contemporary workers (Balinsky, 1970, p. 590, Waddington, 1966, pp. 5-7), and correctly described by the better biology textbooks (examples are Simpson, Pittendrigh and Tiffany, 1957, pp. 352-354 and Keeton, 1972, pp. 551-552 ). A review of eighteen of the latest biology/zoology and eight developmental biology/embryology textbooks reveals an unfortunate trend to slight or even eliminate "traditional" subjects like embryonic similarities and expand upon more "modern" topics such as molecular biology and molecular genetics. Also, many of the modern authors still refer to these embryological phenomena and their evolutionary explanation as recapitulation. Two exceptions are Hopper and Hart (1985, pp. 3-5) and Hickman, Roberts and Hickman (1988, pp. 9, 125-126, 456-457).
Creationists give the impression that recapitulation was a necessary corrolary to evolution invented by Ernst Haeckel (see Gordon, 1987, p. 7). Actually, the idea of recapitulation was held by a number of pre-evolutionary biologists starting with C. F. Kielmeyer in 1793, Lorentz Oken in 1809-1811, J. F. Meckel in 1811 and Etienne Serres in the 1820's and 30's. These authors all incorporated recapitulation into non-evolutionary philosophies, explaining it on other bases such as the unity of nature's laws or relating it to the chain of being or scale of nature. It was later championed by Louis Agassiz as illustrating a three-fold parallelism between embryonic growth, the structural gradation in adult forms and the geologic succession of fossils that represented the history of a particular type (Gould, 1977, chapter 3; Mayr, 1982, p. 469 fol.). Von Baer rejected recapitulation and instead stated that general characters of a group developed first and the more specific ones distinguishing the members of the group appeared later. In later editions of the Origin, Darwin mentions the work of von Baer, Muller (whose views were similar to Haeckel's) and Agassiz but avoids their explanations. He considers the phenomena as representing a law of embryonic similarity and offers his own explanation—that most successful variations appear later in the development of the individual. This fits in with the modern explanation given above. Darwin, of course, wasn't aware of the web of interactions found by the 20th century embryologists that explains why successful modifications tend to occur later in development. Those same embryologists falsified Haeckel's extreme brand of recapitulation—that all evolutionary changes are added to the end of the developmental sequence, causing individuals to develop through a sequence of the adult stages of their ancestors.
Another creationist argument is to claim that the resemblances of early embryonic stages are trivial and superficial: ". . .and since furthermore many of the structures to be developed must be somewhat similar (limbs, head, etc.), it would be natural that the developing embryos would look much alike for the initial stages of their development." (Morris, 1974, p. 73; see also Morris, 1967, p. 24). Another argument is to claim to satisfactorily explain these seemingly anomalous embryonic structures by simply pointing out functions for them. Both Morris and Kofahl list the various derivatives of the pharyngeal pouches and conclude that they reflect "careful planning and design" (Morris, 1974, p. 77); ". . .the facts agree quite logically with the creation viewpoint rather than with an evolutionary explanation." (Kofahl, 1980, p. 104). Evolution also explains their continued existence on the basis of function. But evolution goes further and explains why these structures have the shapes and anatomy that they do. On the other hand, why would a Creator choose to provide blood cells to the early stages of a mammal embryo with an empty yolk sac? Why couldn't the omniscient and omnipotent Creator speed up the growth of the allantois so that a temporary yolk sac placenta is unnecessary? Why should a terrestrial vertebrate embryo produce pharyngeal pouches to induce branchial grooves and gill clefts that in turn induce gill bar tissue to serve as the source of thymus and parathyroid glands which then have to shift their location downward and backward? Evolution explains these incredibly conservative "design" features. The mechanism of mutation and natural selection couldn't proceed in any other way but make use of structures already present and part of the integrative network. Natural selection works more like a tinkerer than an omnipotent designer (Jacob, 1977). On the other hand, special creation would suggest that the egg should develop to the adult by the most direct route without the extraordinary detours that one actually finds (Mayr, 1982, p. 470).
Creationists explain vestigial organs by claiming that they have a function, hence they are not vestigial (Morris, 1974, p. 75; Kofahl, 1980, p. 102; Moore and Slusher, 1974, p. 435), or alternately that they are examples of decay and deterioration, not evolution (Kofahl, 1980; Morris, 1963, p. 44; Morris, 1968, p. 53; Morris, 1974, p. 75). Evolution explains the persistence of vestigial organs which no longer perform their primary function. They may either have an additional primary function, like in the yolk sac example above, and the lymphoid tissue in the appendix (Moore and Slusher, 1974, p.435) or may be retained in embryo because of their secondary integrative function (Yablokov, 1966). Why should the jaws of specially-created toothless animals need teeth (baleen whales) or tooth buds (birds) to insure proper growth of the jaws (Howe, 1985)? And why should birds have a complete set of genic instructions for making fully formed teeth (Kollar and Fisher, 1980) when it is normally never used. Evidently the operation of the tooth-forming gene complex is suppressed in birds but not eliminated because the production of tooth buds may be necessary for the proper growth of the jaws. Similarly mechanisms persist to make fully formed hind limbs as occasionally occurs in whales (Edwords, 1983), or three toed feet as sometimes occurs in horses (Gould, 1980, McGowan, 1984, pp. 147-148), or persistent cervical slits resulting in perforated necks in humans (Arey, 1946, p. 179).
Darwin proposed that vestigial or rudimentary organs resulted from disuse aided by natural selection if the organs were detrimental in the organism's new environment. Moore and Slusher (1974, p. 436) claim that evolution cannot explain vestigial organs at all: deterioration because of disuse is Lamarkian and why would "loss mutations" be selected for losing an organ that might not be beneficial but certainly was not harmful? The accepted evolutionary explanation involves the pleitropic effects of genes (see above) and the gene complexes that produce the various structures. In a cave dwelling organism, for example, selection for gene complexes producing inhanced senses of smell, touch, hearing, etc. may involve actively breaking up gene complexes for eyes because such complexes share some genes (Allee et al., 1949, pp. 672-679). The existence of such overlapping complexes may also prevent the complete elimination of a "useless" structure.
In general, creationists recognize the weakness of their arguments and prefer to avoid dealing with Darwin's most compelling evidence. The Origins Two Models book (Bliss, 1976) never mentions it. The creationist biology textbook (Moore and Slusher, 1974) doesn't describe any of the embryonic similiaries in the chapter on embryology although they are cursorily mentioned in the chapters criticizing evolution (see pp. 432-436). This latter book (p. 435) also makes the inane claim that evolutionists must assume that vestigial nipples in men must have been functional in ancestral males. An organism's developmental system must produce both males and females. A vertebrate embryo goes through an early stage that has a complete set of primordia for both sexes. Once sex hormones take over, one set of structures remains vestigial while the other develops. How do creationists explain this, considering that Adam was made first and Eve was only an afterthought, made from Adam's rib? The question has long been asked: did Adam have a navel? What about nipples? or for that matter, the vestigial remains of oviducts (appendix testis) and vagina (prostatic utricle or vagina masculina)? Similarly women have vestiges of the male ducts. Like the hind limbs of whales, the degree of development of these vestiges varies a great deal from individual to individual (Arey, 1946, p. 297 fol.).
Evolutionary mechanisms tend to modify the later stages of developmental systems because of the web of interacting and integrating parts found in the earlier stages cannot easily be modified. Thus organs and structures that are modified or eliminated in the later stages are retained in the earlier stages because of their integrative functions. Some rudimentary or vestigial organs may persist into the adult stage because they have a secondary adult function in addition to the integrative one. Organs that are no longer useful may become vestigial or eliminated when natural selection breaks up the gene complexes producing these organs in order to assemble more efficient complexes for other organs that are still necessary for survival.
Allee, W. C., A. E. Emerson, O. Park, T. Park and K. P. Schmidt. 1949. Principles of Animal Ecology. Philadelphia: W. B. Saunders Co.
Arey, L. B. 1946. Developmental Anatomy. A Textbook and Laboratory Manual of Embryology. 5th Ed. Philadelphia: W. B. Saunders Co.
Balinsky, B. I. 1970. An Introduction to Embryology. 3rd Ed. Philadelphia: W. B. Saunders Co.
Bliss, R. B. 1976. Origins: Two Models: Evolution Creation. San Diego, CA: Creation-Life Pub.
Darwin, C. R. 1958. The Origin of Species. New York: Mentor Books, New American Library. (reprint of the last edition, with an introduction by Julian Huxley).
Darwin, C. R. 1982. The Origin of Species. New York: The Penguin English Library. (reprint of the first edition, 1859, edited by J. W. Burrow).
DeBeer, G. R. 1940. Embryos and Ancestors. Oxford: Clarendon Press., p>
Edwords, F. , 19,, 83. "Those Amazing Animals: The Whales and Dolphins." Creation/Evolution X: 1-7.
Gordon, P. 1987. "Articles." Origins Research 10(1): 6-7. Spring/Summer.
Gould, S. J. 1977. Ontogeny and Phylogeny. Cambridge, MA: Belknap Press.
Gould, S. J. 1980. "Hen's Teeth and Horse's Toes." Natural History 89(7): 24-28. (July)
Haldane, J. B. S. and J. Huxley. 1927. Animal Biology. Oxford: Clarendon Press.
Hickman, C. P., L. S. Roberts and F. M. Hickman. 1988. Integrated Principles of Zoology. St. Louis: Times Mirror/Mosby College Publishing.
Hopper, A. F. and N. H. Hart. 1985. Foundations of Animal Development. 2nd Ed. New York: Oxford University Press.
Howe, G. 1985. "Further comments on baleen fetal teeth and functions for yolk sac." Origins Research 8(2): 13-14. Fall/Winter.
Jacob, F. 1977. "Evolution and Tinkering." Science 196(4295): 1161-1166. (10 June.)
Karp, G. and N. J. Berrill. 1981. Development. 2nd Ed. New York: McGraw-Hill.
Keeton, W. T. 1972. Biological Science. 2nd Ed. New York: W. W. Norton and Co.
Kofahl, R. E. 1980. The Handy Dandy Evolution Refuter. San Diego: Beta Books.
Kollar, E. J. and C. Fisher. 1980. "Tooth Induction in chick epithelium: Expression of Quiescent Genes for Enamel Synthesis." Science 207: 993-995. (29 February)
Lillegraven, J. A., Z. Kielan-Jaworoska and W. A. Clemens (editors). 1979. Mesozoic Mammals. The first two-thirds of mammalian history. Univ. of California Press.
Mayr, E. 1982. The Growth of Biological Thought. Diversity, Evolution and Inheritance. Cambridge, MA: Belknap Press.
McGowan, C. 1984. In the Beginning. . . Buffalo: Prometheous Books.
Moore, J. N. and H. S. Slusher. (Editors) 1974. Biology: A Search for Order in Complexity. Grand Rapids, MI: Zondervan Pub. House.
Morris, H. M. 1963. The Twilight of Evolution. The Craig Press.
Morris, H. M. 1968. The Bible and Modern Science. Chicago, IL: Moody Press.
Morris, H. M. 1967. Evolution and the Modern Christian. Philadelphia: The Presbyterian and Reformed Pub. Co.
Morris, H. M. (Editor) 1974. Scientific Creationism. San Diego, CA: Creation-Life Pub.
Moscona, A. A. 1961. "How Cells Associate." Scientific American 205(3): 142-162. (September.)
Needham, J. 1930. "The biochemical aspect of the recapitulation theory." Biological Reviews and Biological Proceedings of the Cambridge Philosophical Society V: 142-188.
Saunders Jr., J. W. 1982. Developmental Biology. New York: Macmillan.
Simpson, G. G., C. S. Pittendrigh and L. H. Tiffany. 1957. Life, An Introduction to Biology. New York: Harcourt, Brace and Co.
Sussman, M. 1960. Animal Growth and Development. Englewood Cliffs, NJ: Prentice-Hall, Inc.
Weiss, P. 1939. Principles of Development. A Text in Experimental Embryology. New York: Holt and Co.
Waddington, C. H. 1966. Principles of Development and Differentiation. New York: Macmillan.
Watson, D. M. S. 1951. Paleontology and Modern Biology. New Haven, CN: Yale Univ. Press.
Yablokov, A. V. 1966. Variability of Mammals. Moscow: Nouka Pub. (1974 translation, Amerind Pub. Co.)
(from Frank Sonleitner's critique of Of Pandas and People)
A second edition of "Of Pandas and People" (Percival Davis and Dean H. Kenyon, Haughton Publishing Co., Dallas, Texas) was published in 1993. The first edition of this book, published in 1989 and intended to be a supplementary biology text emphasizing "intelligent design", was reviewed (Scott 1990, Skoog 1989, Padian 1989, Ruse 1989) and extensively critiqued (Sonleitner 1991). It was found to be sloppily produced with many incidental errors (spelling, grammatical, stylistic, numerical errors in tables, incorrectly drawn and/or labeled figures, errors in citations of references) in addition to gross distortions and errors in the presentation of the biological material. The new edition is little changed from the first. Most of the incidental errors have been corrected, some of the material has been rewritten or replaced but nearly all the distortions and errors of scientific facts remain. Some have even been compounded!
Many of the 130 odd grammatical and stylistic errors compiled by retired high school teacher G. E. Peterson have been corrected. But new ones have been committed! Try out this sentence that begins at the end of page vii: "Within intelligent design also the details as to how gradual or abrupt, and over what span of time differ."
Some biological errors that do not compromise the intelligent design arguments are corrected. Thus amino acids no longer have NH3 groups; turtles are no longer amphibians; the authors grudgingly admit that giraffes might occasionally browse leaves from trees; no longer is it claimed that paleontologists could not distinguish between a placental wolf and a Tasmanian wolf skull—the authors even admit that marsupials might differ from placentals in more ways than just the presence or absence of a pouch. Some of the figures have been redrawn or replaced; those with errors have been corrected. In Figure 4-14 the halloween mask face of the Australopithecus africanus has been fixed, but not the incorrect thorax.
The footnoted references, which were hidden in the Teachers' Guide in the first edition, now appear at the end of each Excursion Chapter. Excursion chapters 1, 2 and 6, which previously didn't have any references, now do, and additional ones have been added to the other chapters. The citations are as sloppy as ever—I have found nearly a dozen mistakes in the new ones.
With a few exceptions to be noted below, the changes in the text are cosmetic. One change that pervades the book is that most of the references to "evolution" and "evolutionists" have been changed to "Darwinism" and "Darwinists". This is apparently to make a distinction between "evolution" which can mean "change in living things over time" and "Darwinism" which refers to the mechanism of mutation and natural selection (Glossary, p. 149, A Note to the Teachers, pp. 155-156.) Changes in living things over time as documented in the fossil record is accepted as a fact (pp. 26, 155-156) and the authors would appear to believe in a kind of progressive creation, although they nowhere specify any such details of their intelligent design hypothesis. I suspect this was done so that creationists of every variety can read their own doctrine into the book.
The Overview chapter has few changes. There has been some shuffling of paragraphs on pp. 18-19 and the last section has been modified to reflect changes in Excursion chapter 6. The partial Dayhoff cytochrome c matrix displayed on p. 37 is free of errors.
In Excursion chapter 1 (the Origin of Life), the section titled: Scientific Case for the Intelligent design of Life, has been rewritten and the authors propose a new law: "Information never arises from physical or chemical causes alone." Because this is really a conclusion based on the assumption of unknowable, untestable, supernatural designers of DNA, it obviously fails the criteria for a scientific law.
In Excursion chapter 2 (Genetics and Macroevolution) the section describing Ambrose' ideas on how evolutionary change might come about has been rewritten, but without changing its grossly inaccurate content. The authors still insist that many features of the giraffe's "adaptational package" are unique to the giraffe. The stone plants and the accompanying figure in the first editions have been omitted.
There are no major changes in Excursion chapter 3 (the Origin of Species). Phillip Johnson's book has been added to the Suggested Reading / Resources.
In Excursion chapter 4 (The Fossil Record), the sections on the origin of reptiles and of plants have been omitted. The discussion of Homo erectus has been greatly shortened and a discussion of the mitochondrial Eve added. There is also a new discussion of the mammal-like reptiles and a more accurate description of Archaeopteryx, but it is claimed that natural selection could not be responsible for the evolution of feathers. The authors mention the new finding that the whale Basilosaurus had tiny hind feet. They do not mention Gish's contention that this specimen is a reptile, but on the basis of Gingerich's speculation that the tiny feet aided in copulation, claim that this is an example of intelligent design. They also cite Stephen Gould as saying that there is not enough time in the fossil record for the evolution of whales from mesonychids.
There are no major changes in Excursion chapter 5 (Homology). The authors omit their previous short discussion of cladistics. Although they continue to couch some of their examples in terms of recapitulation, they now specifically say that recapitulation is false (p. 129).
Excursion chapter 6 (Biochemical Similarities) has undergone the most extensive revision. Sections on the complex mechanism of blood clotting and on the origin of proteins have been added. It is interesting to note that the blood clotting mechanism has been used by Jacob (1977) as an example of "tinkering" by natural selection! To make room for this new material, the section on cytochrome c has been greatly abridged. Any possibility that this data might support evolution (and such a discussion did appear in the first edition) has been eliminated. Now the authors, even though they admit that they are comparing living forms, none of which is ancestral to any other, fly in the face of reason and logic and insist that one should find intermediate degrees of divergence of cytochrome c when comparing carp, bullfrogs, turtles, etc. This misinterpretation of the cytochrome c data was pioneered by Denton (1985) and has been referred to as "Denton's error" by a number of evolutionary authors and reviewers (Landau 1990, Thwaites 1989, Thwaites 1990). According to Davis and Kenyon, the biochemical evidence totally refutes evolution. On this basis alone, I must conclude that the second edition of Pandas is a retrograde development—it is worse than the first edition!
Charles Thaxton's "A Word to the Teacher" has been supplanted by one written by M. D. Hartwig, and S. C. Meyer, in another attempt to make supernatural mechanisms viable scientific explanations.
Denton, M. 1985. Evolution: A Theory in Crisis. Bethesda, MD: Adler and Adler.
Jacob, F. 1977. Evolution and Tinkering. Science 196: 1161-1166 (see p. 1165).
Landau, M. 1990. Protein Sequences and Denton's Error. Creation/Evolution 9(2): 1-7 (Winter).
Padian, K. 1989. Gross Misrepresentation. Bookwatch Reviews 2(11): 2-3.
Ruse, M. 1989. They're Here! Bookwatch Reviews 2(11): 3-4.
Scott, E. C. 1990. Of Pandas and People. NCSE Reports 10(1): 16-17 (Jan.-Feb.)
Skoog, G. 1989. A View From the Past. Bookwatch Reviews 2(11): 1-2.
Sonleitner, F. J. 1991. What's Wrong With Pandas? 106 pp. National Center for Science Education.
Thwaites, W. 1989. Evolution: A Theory in Crisis. NCSE Reports 9(4): 14-17 (July-Aug.)
Thwaites, W. 1990. Molecular Clocks and Creationism. NCSE Reports 10(5): 14-16 (Sept.-Oct.)
A second edition of "Of Pandas and People" (Percival Davis and Dean H. Kenyon, Haughton Publishing Co., Dallas, Texas) was published in 1993. In "A Note to Teachers" included in the back of the book, Mark Hartwig and Stephen Meyer say (p. 154):
"The purpose of this text is to expose your students to the captivating and the controversial in the origins debate ... and encourage them to grapple with ideas in a scientific manner.
Pandas does this in two ways. First, it offers a clear, cogent discussion of the latest data relevant to biological origins ...
Second, Pandas offers a different interpretation of current biological evidence ... a clear alternative, which the authors call "intelligent design."
If Pandas really did this, it would be very nice. But Pandas fails in two ways:
(1) It provides no alternate explanation. "Intelligent design.i.Intelligent design;" is like the emperor's new clothes. Behind the impressive name lurks nothing but a totally mysterious, invisible and inaccessible supernatural agent, a concept whose information content and explanatory usefulness is zero.
(2) In order to persuade the reader to accept this "explanation", Pandas inundates the reader with a flood of disinformation about biology, biologists and evolution.
In "The New Pandas: A First Look", I pointed out that the footnoted references, now appear in the book itself. Also, the Glossary (pp. 149-151) has been expanded; the Acknowledgements section (p. iii) now includes the professional affiliations of the critical reviewers and brief background descriptions of the authors and contributors are given on p. 169.
A pervading change in the book is that most of the references to "evolution" and "evolutionists" have been changed to "Darwinism" and "Darwinists" to make the distinction between "evolution" which can mean "change in living things over time" and "Darwinism" which refers to the mechanism of mutation and natural selection (Glossary, p. 149, A Note to Teachers, pp. 155-156.) Changes in living things over time as documented in the fossil record is accepted as a fact (pp. 26, 155-156.) "Intelligent design" apparently refers to a kind of progressive creation. In regard to this, Pandas mentions the possibility that blueprints of previous organisms might have been used in the creation of later ones (p. 42).
Is the new edition improved? Only a few minor errors and shortcomings of the 1st edition have been corrected. The great majority of the errors, extensively critiqued in "What's Wrong with Pandas?" still remain. The new material is just as unreliable and will be dealt with below. Pandas has changed its discussion of the cytochrome c data (Overview and Excursion chapters 6) to reinforce its incorrect view that such biochemical data disproves evolution. In this respect, the new edition is worse than the first.
This has been rewritten, involving only cosmetic changes.
On p.4 Pandas says that there is geological evidence that there was an oxygen atmosphere earlier than the development of life. This is not correct. There is evidence for small amounts of oxygen in the atmosphere of later Precambrian times as a result of the photosynthetic activities of some of the prokaryote organisms.
Figure 1 has been corrected. The amino acid structures now have NH2 groups instead of NH3 groups.
In column 1 of p. 12, Pandas now say that some mutations may be neutral. In column 2, they admit that giraffes feed in tree tops. In column 2 of p. 13, Pandas cites brachiopods (see p. 72 for reference) as another example of interdependence of structures. There is nothing particularly special about brachiopods in this regard.
On pp. 18-19, some of the paragraphs have been shuffled around between the sections on Genetic Drift and The Founder Effect.
The "avian complex" (p. 23, column 2, top) will be discussed in connection with Excursion Chapter 4.
Here Pandas states: "The existence of fossils with enormous variety is a fact, and so are the changes in the distribution of those fossils over time;..." If we accept that all life comes from life, as Pandas insists then the younger fossils must have descended from the older ones, and we have a documented evolutionary history! Only if we assume spontaneous generation by intelligent designer intervention, can we reconcile the intelligent design hypothesis with these facts. And this produces a kind of "progressive creationism" as described by Ambrose (1982), somewhat akin to theistic evolution!
There is a new and improved (really) Figure 6 on p. 28.
Here Pandas admit that the American wolf and the Tasmanian wolf differ in more characters than just the presence or absence of a pouch and the statement that a paleontologist could not distinguish between fossils of the two has been deleted.
The introductory paragraph has been rewritten. There is a new figure on p. 36. The Dayhoff matrix in Table 1 (p. 37) has been redone and the 6 paired errors in the 1st edition corrected.
In the 1st edition, Pandas spoke of a "ladder" of evolution (column 1, p. 37.) Now Pandas notes that evolution follows a branching tree pattern (column 2, p. 37). Yet Pandas still insists that the living forms included Table 1 should display intermediate cytochrome c patterns if Darwinism is correct! There is no logical reason for this assertion! Even in terms of anatomy, the bullfrog, for example, is a highly specialized amphibian and is not intermediate between the fishes and reptiles. For the true intermediate forms one must look to the fossil amphibians in the Paleozoic.
This was originally a part of the preceding section. The subject has been eliminated from Excursion Chapter 6.
This section has been extensively rewritten. Pandas' claim that the fossil record also shows distinct clusters (p. 39 bottom of column 2) is not true.
"The amphibians grade so insensibly into the reptiles that the assignment of certain fossils becomes rather arbitrary...The same is true of the border between mammal-like reptiles and the mammals." (Mayr, 1963, p. 596.)
Ambrose, E. J. 1982. The Nature and Origin of the Biological World. Halsted Press. New York.
Mayr, E. 1963. Animal Species and Evolution. The Belknap Press of Harvard University Press. Cambridge.
There are only a few minor changes. The amino acid structures in Figure 1-5 (p. 51) have been corrected to have NH2 groups instead of NH3 groups.
Pandas' reference 6 (Clemmey and Badham, 1982) summarizes the evidence for oxygen in the Precambrian atmnosphere. Before the advent of life, free oxygen might have been generated through photodissociation of water by ultra-violet rays. They also mention that several of the ‘origin of life' scenarios: prebiotic evolution in space, possibly in comets, and among pores in the dust grains of the early Earth regolith, do not require a reducing atmosphere.
Here Pandas claims that "Information never arises from physical or chemical causes alone" is an empirically based generalization or law of nature. This is supposed to be based on "our universal experience that such sequences are the result of intelligent causes" (p. 58). But this is not the case. It is not our empirical experience that supernatural designers have created DNA! Intelligent design proponents can only postulate that DNA sequences were produced by intelligent design. In fact, in the section "A Note to Teachers" (see p. 160), this generalization is said to be a prediction of the intelligent design hypothesis! Pandas is indulging in circular reasoning. The generalization upon which they base their hypothesis is itself based on that hypothesis.
Towards the end of this section (bottom of p. 57), Pandas advises, "Well-designed experiments on the origin of life should continue." One might ask, "Why?" If life originated as the result of a supernatural, intelligent designer, no experiments will ever yield any understanding of the phenomenon. Maybe Pandas knows something but they're not telling us. What do Pandas consider to be a well-designed experiment? And what possibly could the experimenter be looking for?
Clemmy, H. and N. Badham. 1982. Oxygen in the Precambrian atmosphere: An evaluation of the geological evidence. Geology 10(3): 141-146.
Nothing of importance has been changed in this chapter. Table 2-1 now has a legend. The term "messages" is substituted for "Specifications" in Figure 2-3. The discussion of the "stone plants" and the accompanying Figure 2-6 have been omitted. The book by Yockey listed under Suggested Reading/Resources now has a 1992 publication date but the title is wrong! The correct title is "Information Theory and Molecular Biology."
Certain parts of the chapter have been more or less rewritten but without changing any arguments or adding anything new.
This section, which incorporates Ambrose' ideas (Ambrose, 1982) on the nature of evolutionary change has been extensively rewritten but without correcting any of the grossly inaccurate content. Ambrose claims that the application of information theory disproves evolution (p. 69, top of 2nd column). Yockey (1992) disagrees with this and essentially corroborates what I previously said about evolutionary change.
In two place in column 1 of p. 71, Pandas admits that giraffes might use their long necks to browse in the trees!
Ambrose, E. J. 1982. The Nature and Origin of the Biological World. Halsted Press. New York.
Yockey, H. P. 1992. Information Theory and Molecular Biology. Cambridge University Press, Cambridge.
There are only a few minor changes in this chapter that require comment.
The unnumbered figure at the top of p. 82 has two labels "Original Gene Pool" and "New Gene Pool" added to it. There is a new version of Figure 3-4 (on p. 84). Phillip Johnson's book, Darwin on Trial, has been added to the Suggested Reading/Resources.
Near the bottom of the first column on p. 78 Pandas gives an example of a phylum with only one species, but the names are reversed! It should be the phylum Caryoblastea containing the one species Pelomyxa palustris. One might rightly guess that these are highly unusual organisms! They are giant single cells visible to the naked eye and the most primitive of eukaryotes. They have membrane-bound nuclei but no endoplasmic reticulum, Golgi bodies, mitochondria, chromosomes or centrioles. They seem to divide as bacteria do; there being no sign of a mitotic process (Margulis and Schwartz, 1982).
In column 2 of p. 78, Pandas says that "the challenge is discovering the extent of change that takes place..." I think the real challenge is discovering how species were designed in the first place!
Pandas still hasn't got the quotes straight! Mayr's statement (Mayr, 1963, p. 12) is attributed to Simpson (Simpson, 1964, p. 81) and vice versa.
In the 2nd column of p. 88, Pandas has a new sentence:
"Moreover, a growing number of scientists accept natural selection as a reasonable explanation for the modification of traits but not for the origins of new structures."
and gives 6 citations (reference 5) to back it up. Although this statement paraphrases Rieppel (1990, p. 303), I think the sentence is misleading. Whether we are dealing with a modified trait or the appearance of an incipient structure, we are dealing with variation which originates from mutation and/or genetic recombination. Natural selection only preserves modifications and new structures, guiding the course of evolution by controlling the accumulation of such variations and combinations of them through elimination or preservation. Reippel cites Sober (1984, p. 197) who suggests that the dorsal plates of Stegosaurus originated fortuitously. Once they occurred they may have performed a number of adaptive functions and preserved by natural selection. On the other hand, several of the authors cited have difference ideas about the source of variation. Margulis (Mann, 1991, p. 379) thinks it results from the acquisition of symbionts; McDonald (1983, p. 97) postulates stress-induced variation; Ambrose (1982, p. 131, but esp. 143) postulates a designer tinkering with the DNA during speciation by punctuated equilibrium.
Ambrose, E. J. 1982. The Nature and Origin of the Biological World. John Wiley and Sons. New York.
Mann, C. 1991. Lynn Margulis: Science's Unruly Earth Mother. Science 252: 378-381. (19 April).
Margulis, L. and K. V. Schwartz. 1982. Five Kingdoms: An Illustrated Guide to the Phyla of Life on Earth. W. H. Freeman and Co., San Francisco.
Mayr, E. 1963. Animal Species and Evolution. The Belknap Press of Harvard University Press.
McDonald, J. F. 1983. The Molecular Basis of Adaptation: A Critical Review of Relevant Ideas and Observations. Annual Review of Ecology and Systematics 14: 77-102.
Reippel, O. 1990. Structuralism, Functionalism, and the four Aristotelean Causes. Journal of the History of Biology 23(2): 291-320.
Simpson, G. G. 1964. This View of Life. The World of an Evolutionist. Harcourt, Brace and World.
Sober, E. 1984. The Nature of Selection: Evolutionary Theory in Philosophical Focus. University of Chicago Press. Chicago and London.
Modifications to this chapter include the deletion of the sections on the origin of reptiles and plants (Figure 4-12 from the 1st edition has been deleted) and a rewriting of the sections on the origin of mammals and Archaeopteryx. The material on Homo erectus which was mostly wrong has been greatly reduced and a section on the mitochondrial Eve added.
Feature No. 1 (that fossils encapsulate information about past, extinct forms) has been omitted from this section and the following one.
In this section, Figure 4-2 has been revised. Only animal phyla are shown (Pandas still doesn't identify them) thereby omitting a number of phyla (mostly plants) whose origins either predate the beginning of the Cambrian or occur much later. This bias accentuates the "Cambrian explosion." The figure has been marginally improved by indicating the known fossil record (solid line) and presumed fossil record (dotted line) of each phylum, showing quite clearly that the origin of most of the animal phyla is only presumed to have occurred at the beginning of the Cambrian.
This section has been rewritten and is fairly accurate. Pandas even admits that, with regard to the mammal-like reptiles, "Indeed, it does appear that they provide Darwinists with a superior example of a transitional series." (Pandas, p. 100)
Actually they provide all evolutionists, including non-Darwinists such as Grasse (Grasse, 1977) and even "progressive creationists" such as Richard Owen (Desmond, 1982), with this superior example! Pandas' speculation that the information for mammalian structures "may have existed, unexpressed, in the genome of the earliest Therapsids before they diversified" is pure speculation and would involve totally unknown genetic mechanisms. It is not clear why Pandas bothers to make this speculation, unless it is to convince one that the evolution of Therapsids is simply "horizontal variation."
"The absence of unambiguous transitional fossils" is no longer illustrated by whales. Gould (1994) summarized all but the latest remarkable transitional whale fossils found in the past few years, including Pakicetus, the amphibious mesonychid-like form, Ambulocetus and Indocetus which are four-legged whales without modified tails, and the new Basilosaurus with the tiny regressed hind legs. Gould obviously believes that whales evolved from mesonychids! How is this fact reconciled with Pandas' claim that Gould has calculated that there was not enough time to evolve a Basilosaurus from the Mesonyx by punctuated equilibrium? The claim is false. Steven Stanley argued that there wasn't time to evolve the whales from mesonychids by phyletic gradualism but there wouldn't be any problem if most of the evolution occurred by punctuated equilibrium at speciation events (Stanley, 1981, pp 93-95). This argument is discussed both by Augros and Stanciu (1987, p. 175) and by Johnson (1991, p. 51) which is probably where Pandas encountered it but its presentation here is hopelessly garbled.
The latest whale find is the 46 million year old Rodhocetus, whose legs were shorter than those of Ambulocetus, its sacral vertebrae not fused and not articulating with the pelvis and whose massive tail vertebrae indicate that it had powerful tail flukes (Gingerich et al, 1994; Zimmer, 1995) thus filling a gap between Ambulocetus and Basilosaurus. We now have a complete set of fossils documenting the major steps in whale evolution! Of course it is not fair to criticize Pandas for not mentioning discoveries that were announced after Pandas had gone to press, but this situation illustrates that creationists, whose ideas rely on gaps in the fossil record, are fighting a rear-guard action which they are losing.
Paleontology is continually finding new fossils that shed light on the fish-amphibian transition. Thus Pandas account of the origin of amphibians is years out of date. Recent publications discuss fossils that are closing the gap between fishes and amphibians. Certain crossopterygian (sarcopterygian) fishes of the family Panderichthyidae are so similar to the earliest amphibians, Ichthyostega and Acanthostega, that, in some instances, it is difficult to tell if a fossil is a fish or an amphibian (Ahlberg, 1991; Ahlberg and Milner 1994.) Acanthostega had fishlike internal gills and ventilation. The limbs had supernumerary digits and were flipper-like; the pelvis was similar to that of a fish (Gee, 1991). On the other hand, the paired fins of the crossopterygian fish Sterropterygion brandei show tetrapod-like features including details of the shoulder girdle; a primitive elbow joint in the pectoral fins and a primitive tarsal joint in the pelvic fins (Rackoff, 1980).
The evolution of amphibians from fish occurred in a chunk of space-time including all the continents of the earth over a period of 28 million years. We have fossils from only a dozen or so specific points in space and time during that entire period so it is not surprising that there are gaps in our knowledge of that process.
Based on its feathers, Pandas claims "that Archaeopteryx was an accomplished flyer, because they provided an airfoil superbly adapted for flight." The superb airfoil is a reference to the fact that the feathers have a vane asymmetry similar to that of extant birds which gives them a wing-like cross-section. A recent study (Speakman and Thomson, 1994) has shown that "the extent of asymmetry in the feathers of Archaeopteryx is only slight, significantly lower than in modern flying birds and comparable to that of extant nonflying birds." Other studies have shown that Archaeopteryx' wrist lacks all the key features for flight found in the modern bird (Vazquez, 1992) and that the flight muscles were too small to provide powerful sustained flight (Speakman, 1993). Thus the evidence shows that Archaeopteryx did not have fully modern feathers and was most likely a very weak flyer. Lacking the full "avian complex" Pandas claims it couldn't fly at all; hence natural selection couldn't have evolved the feather. But if it wasn't "intended" to fly, why did the "intelligent" designer give it the "superb airfoil"?
Evolutionists explain the intermediate nature of Archaeopteryx by saying that it is a transitional form in the evolution of birds. Design proponents have no explanation for its intermediate form except that some unknown and unknowable supernatural designer desired to make it so! Recently, somewhat younger fossil birds have been found from the Lower Cretaceous period that are intermediate between Archaeopteryx and modern birds (Kurochkin, 1985; Sereno and Chenggang, 1992; Sanz, Bonaparte and Lacasa, 1988). The oldest of these, the sparrow-sized Sinornis from China is about 15 million years younger than Archaeopteryx. It looks very much like a small Archaeopteryx, but it has a shorter body, a much shorter tail, a stronger pectoral girdle and forelimbs for much more powerful flight; the wing has an advance wing-folding mechanism and the hind feet are modified for perching. About 5 million years younger than Sinornis is the Spanish Las Hoyas bird which is slightly more modern in form. And the Mongolian Ambiortus, about 5 million years younger than the La Hoyas bird, is even more modern! This is a wonderful series of intermediate forms representing an evolutionary series in the evolution of the "avian complex." Do the design proponents dare to suggest that they are trial efforts of a much less than omnipotent and omniscient designer who has to produce new designs in stages?
In Figure 4-10, the drawing of an unspecified Triassic thecodont has been replaced with one of an unspecified Theropod dinosaur.
Corrections have been made to Figures 4-12 thru 4-14 (formerly Figures 4-13 thru 4-15). No longer does Figure 4-12 show Pliopithecus and Oreopithecus persisting to the present time; numbers for the cranial capacities of A. boisei and A. robustus have been added to Figure 4-13 and the halloween mask skull of Australopithecus africanus in Figure 4-14 has been replaced. In the text, almost all the discussion of Homo erectus, which was fraught with errors, has been eliminated.
Added to this section is a discussion of the mitochondrial Eve hypothesis. Unfortunately it gives a muddled explanation for the use of mitochondrial DNA. Consider this sentence, referring to mutations in mitochondrial DNA: "The reason they do is that such mutations are not corrected as they are in nuclear DNA." What is that supposed to mean?
Actually, mitochondrial DNA is useful for "tracking the relationships among peoples" because it is transmitted to offspring maternally, i.e. only through their mother. As generations go by, however, the mitochondrial DNA of any females who produce only sons is lost, and eventually, the mitochondrial DNA of the species will be reduced to one lineage stemming from one ancestral female. This is the mitochondrial Eve. It definitely does not mean that all races of humanity owe their origin to a single female ancestor. They owe their origin to an entire population of females and males. It is just that the mitochondrial DNA of only one of those females has survived to the present. To make sure that all possible errors have been committed, Pandas reports the citation (reference 23) incorrectly. It should be A. C. Wilson et al.
The quote from Thomson (reference 24: Thomson, 1982) stops just short of where Thomson presents a solution to breaking the "circularity in the approach"—which is to use cladistic analysis! Clever (but dishonest) Pandas! Is this why they eliminated their discussions of cladistics from the new edition?
Design adherents, in claiming that Homo erectus and other hominids are just apes and that culture appeared abruptly, are only displaying their ignorance of the relevant facts. The anatomical evidence is clear that the hominids are, to various degrees, pre-men; the youngest specimens of H. erectus grade into modern man through presapiens (archaic sapiens) forms. And culture first appeared in a very simple form, called Oldowan, dating from 500,000+ years ago and associated with the early Homo species, and developed through a sequence of stages of ever increasing complexity: Acheulian (75,000—150,000 years ago, associated with H. erectus), Mousterian (45,000 years ago associated with Neandertal man), and finally Aurignacian (40,000 years ago), Perigordian (30,000 years ago), Solutrian (20,000 years ago), Magdalenian (15,000 years ago) and Azilian (10,500 years ago) associated with Cro-Magnon (modern) man (Howell, et al, 1965).
Ahlberg, P. E. 1991. Tetrapod or near-tetrapod fossils from the Upper Devonian of Scotland. Nature 354: 298-301 (28 November).
Ahlberg, P. E. and A. R. Milner. 1994. The origin and early diversification of tetrapods. Nature 368: 507-514. (7 April).
Augros, R. and G. Stanciu. 1987. The New Biology: Discovering the Wisdom in Nature. New Science Library. Shambhala. Boston and London.
Desmond, A. 1982. Archetypes and Ancestors: Palaeontology in Victorian London 1850-1875. University of Chicago Press. Chicago.
Gee, H. 1991. The brave vertebrate venture. Nature 354: 268-269. (28 November).
Gingerich, P. D., S. M. Raza, M. Arif, M. Anwar and X. Zhou. 1994. New Whale from the Eocene of Pakistan and the origin of cetacean swimming. Nature 368: 844-847 (28 April). See also: Novacek, M. J. 1994. Whales leave the beach. Nature 368: 807 (28 April).
Gould, S. J. 1994. Hooking Leviathan by Its Past. Natural history 103(5): 8-15. (May).
Grasse, P.-P. 1977. Evolution of Living Organisms: Evidence for a New Theory of Transformation. Academic Press, New York.
Howell,F. C. and The Editors of LIFE. 1965. Early Man. Time Inc., New York.
Johnson, P. E. 1991. Darwin on Trial. Regency Gateway, Washington, D. C.
Kurochkin, E. N. 1985. A True Carinate Bird from Lower Cretaceous Deposits in Mongolia and Other Evidence of Early Cretaceous Birds in Asia. Cretaceous Research 6(2): 271-278.
Rackoff, J. S. 1980. The Origin of the Tetrapod Limb and the Ancestry of Tetrapods. In: Panchen, A. L. (Editor). 1980. The Terrestrial Environment and the Origin of Land Vertebrates. Academic Press. London, New York. pp. 255-292.
Sanz, J. L., J. F. Bonaparte and A. Lacasa. 1988. Unusual Early Cretaceous birds from Spain. Nature 331: 433-435. (4 February). See also: Cracraft, J. Early evolution of birds. Ibid. 389-390.
Sereno, P. C. and R. Chenggang. 1992. Early Evolution of Avian Flight and Perching: New Evidence from the Lower Cretaceous of China. Science 255: 845-848. (14 February). See also: Barinaga, M. 1992. Evolutionists Wing It With a New Fossil Bird. Ibid. 796.
Speakman, J. R. 1993. Flight capabilities in Archaeopteryx. Evolution 47(1): 336-340.
Speakman, J. R. and S. C. Thomson. 1994. Flight capabilities of Archaeopteryx. Nature 370: 514. (18 August).
Stanley, S. M. 1981. The New Evolutionary Timetable: Fossils, Genes, and the Origin of Species. Basic Books, Inc., New York.
Thomson, K. S. 1982. Marginalia: The meanings of evolution. American Scientist 70(5): 529-531. (September-October).
Vazquez, R. J. 1992. Functional Osteology of the Avian Wrist and the Evolution of Flapping Flight. Journal of Morphology 211: 259-268.
Zimmer, C. 1995. Back to the Sea. Discover 16(1): 82-84. (January).
There are only a few minor changes in this chapter. All the old errors are still intact.
Pandas appears to have some difficulty with the concepts of parallel and convergent evolution. In the first edition, on p. 117 they claimed that the American wolf and the Tasmanian wolf are examples of parallel evolution, the vertebrate eye and the squid eye are an example of convergent evolution and on p. 120, the common features of the two pandas are the result of parallel evolution. In the second edition, the two terms are interchanged, the wolves and the pandas are said to represent convergent evolution and the vertebrate and squid eye parallel evolution! Whether similarities are due to convergence or parallelism depends on the closeness of relationship of the forms involved. Thus the vertebrate and squid eyes are definitely a case of convergence, the wolf-like forms are convergent and the pandas may or may not be considered convergent (the Ursidae (bears) and Procyonidae (racoons) are considered close relatives.)
In the second columns of pp. 127 and 133, Pandas omit their previous discussion of cladists.
Some people have claimed that the panda's thumb is incorrectly labeled in Figure 5-6. Labeled diagrams of the panda's hand (Gould, 1978; Tabin, 1992) indicate that Figure 5-6 is correct! (How did Pandas manage that?) In addition to asking why the intelligent(!) designer gave the panda an ersatz thumb instead of a true opposable thumb, such as the primates possess, why is it that the panda's foot also has an enlarged tibial sesamoid, but not enlarged enough to be a "panda's big toe"? (Gould, 1978, p. 30; Roth, 1988, p. 21).
Here Pandas mention the mitochondrial DNA of some 20 million year old trees as an unusual type of fossil. In the reference cited, Gould (Gould, 1992) discusses the DNA extracted from leaves of Magnolia and Taxodium (the bald cypress) recovered from Miocene lake beds in Idaho. Gould's paper is subtitled "A colorful 20-million-year-old leaf is an elegant test of the theory of evolution." The changes in gene sequences between these fossils and their modern counterparts is a remarkable confirmation of evolution, involving the accumulation of neutral mutations, and by implication, a confirmation of molecular clocks.
Virtually all the homologies of vertebrate comparative anatomy were identified by early 19th century pre-evolutionary anatomists. Most of these structures not only share common connections and relations with other structures but also a common embryological origins. But there are exceptions which were discussed and summarized by De Beer (1958, 1971). De Beer's 1971 monograph served as the basis for chapter 7 of Denton (1985) and is mentioned by Johnson (1991) in his Research Notes to Chapter 5 (p. 172). These authors have misread de Beer to mean that no homologous structures have similar embryological origins or are even determined by the same genes! Denton concludes that homology is a useless concept although de Beer did not! (de Beer, 1958, p. 152).
These problems have been further considered by Roth (1984, 1988) and in a new book on homology (Hall, 1994). Complexities arise because there is not a simple congruence between the genes, developmental mechanisms and morphological features. Not only can a morphological feature evolve, but also the developmental mechanism producing it. Complexes of pleiotropic genes interact by way of a hierarchy of interrelated developmental mechanisms to produce the morphological phenotypic character. The recent discovery of homeotic (homeobox) genes governing the anterior-posterior differentiation of a wide variety of organisms has revealed an extensive homology within their genetic regulatory systems, and has helped to explain in part some of the difficulties mentioned by de Beer. For more on homeotic genes, see the new supplement: Homology in Developmental Genetics: the homeotic genes.
At the end of this section in the first edition, Pandas admitted that the coccyx "seems to be homologous to a tail." If this is accepted then, as a tail, the coccyx is definitely vestigial.
Near the top of the second column on p. 129, Pandas has added some sentences indicating that the biogenetic law has been rejected by science. In the paper cited (Thomson, 1988), Thomson makes clear that it is the Meckel-Serres and Haeckelian type of recapitulation that has been rejected. On the other hand he says, "Von Baer and his predecessors had hit upon a fundamental fact of nature" and later, "Although von Baer was an avowed anti-Darwinist, what has become known as "von Baerian recapitulation" is wonderful evidence for the fact of evolution.." Interestingly enough, nowhere in this paper do I find the statement attributed to Thompson by Pandas that "The biogenetic law as a proof of evolution is valueless."
Raff and Kaufman (1983) do say that the biogenetic law is "a mirage" on p. 19, but later in the book (chapter 5, especially pp. 154 fol. and chapter 6) they give a modern explanation of von Baer's laws, which is the same as that given in the "What's Wrong With Pandas" supplement, "Embryos and Evolution." It would seem that Pandas don't read the references they cite, because Raff and Kaufman (1983) is a very good summary of the interrelationships of embryology and evolution, containing much important evidence for evolution, including discussions of punctuated equilibrium, molecular clocks, how homeotic genes govern body plans and the two chapters mentioned dealing with the true nature of recapitulation phenomena.
At the end of this section, Pandas states, "...scientists have recently recognized that embryonic structures once thought functionless actually play important roles in the formation of more advanced structures to follow." The example given in the citation (Raff and Kaufman, 1983, p. 18) dates back to 1886—more than 108 years ago—which is hardly recent!
Although Stephen Gould may have said that homology supports common design as well as it does common ancestry, he does not say it in the paper cited (Gould, 1987).
de Beer, G. R. 1958. Embryos and Ancestors. 3rd Edition. Clarendon Press, Oxford.
de Beer, G. R. 1971. Homology: an Unsolved Problem. Oxford Biological Readers, No. 11. Oxford University Press. London.
Denton, M. 1985. Evolution: A Theory in Crisis. Adler and Adler. Maryland.
Gould, S. J. 1978. The Panda's Peculiar Thumb. Natural History LXXXVII(9): 20-30 (November).
Gould, S. J. 1987. The Panda's Thumb of Technology. Natural History 96(1): 16-23. (January).
Gould, S. J. 1992. Magnolias from Moscow. Natural History 101(9): 10-18 (September).
Hall, B. K. (Editor) 1994. Homology: The hierarchical basis of comparative biology. Academic Press. New York.
Johnson, P. E. 1991. Darwin on Trial. Regency Gateway. Washington, D. C.
Raff, R. A. and T. C. Kaufman. 1983. Embryos, Genes, and Evolution: The Developmental-Genetic Basis of Evolutionary Change. Macmillan Pub. Co., Inc. New York.
Roth, V. L. 1984. On homology. Biological Journal of the Linnean Society 22: 13-29.
Roth, V. L. 1988. The Biological Basis of Homology. In: Humphries, C. J. (Editor). Ontogeny and Systematics. Columbia University Press. New York. pp. 1-26.
Tabin, C. J. 1992. Why we have (only) five fingers per hand: Hox genes and the evolution of paired limbs. Development 116(2): 289-296 (October).
Thomson, K. S. 1988. Marginalia: Ontogeny and phylogeny recapitulated. American Scientist 76(3): 273-275 (May-June).
Because this chapter has been extensively rewritten, it is appropriate that a new outline be given:
All but 4 of the original 16 figures have been deleted. Of the those remaining:
The new Figure 6-1 has "Organelles" corrected labeled as "Rough endoplasmic reticulum." Recall that the old Figure 6.6 was a Dayhoff matrix (similar to Figure 6 (p. 37 in the Overview section) except that it included 25 species and contained 13 sets of paired errors! It is now gone. A new Figure 6-4 is similar to the old Figures 6-12 and 6-13. New Figures 6.5 and 6.6 illustrate the new section on blood clotting. Old Table 6.1 has been deleted.
This section has been partly rewritten. The paragraph on chirality (asymmetry or handedness of molecules) has been deleted.
The paragraphs explaining the genetic code have been deleted.
This section has been greatly abbreviated. Subsections on Family Trees, The Search for Intermediate Sequences, The Data Fit a Pattern, the Molecular Clock Hypothesis and Multiple Molecular Clocks have been deleted. All discussion of how evolution explains these data has been stricken, although a section on molecular clocks still exists in the Overview Section (p. 39) as a "vestige" from the 1st edition.
In contrast to Pandas who insist that evolution cannot possibly explain the cytochrome c data, Dayhoff, Park and McLaghlin (1972) state, "From protein sequence data alone, it is possible to derive a phylogenetic or evolutionary tree which shows in detail the nature of the ancestral relationships of present-day species." They present such a tree in their Figure 2-1 and say, " This tree...has the same topology (order of branching without regard for changes in the length of branches or in the angles between them) as trees derived from morphological or other biological considerations." In making the tree, they "use a method that involves reconstructing plausible ancestral sequences from our knowledge of present-day sequences." From their published sequences of cytochrome c from living forms and that of the postulated common ancestors (foldout on p. D-367), I have produced Figure 6.1 which is to be compared with Pandas' Figure 9 (p. 38) or 6-4 (p. 140). The common ancestral sequences are represented by the nodes numbered 2—6. The numbers beside the branches of the tree are the number of amino acid changes occurring along those branches. Examination of this tree (and of the original sequences in Dayhoff, 1972) illustrate that nodes 2 and 3 are intermediate between the horse (or rabbit) and node 6 (the common ancestor of the vertebrates.) The same holds true for nodes 3 and 4. Yet the total number of changes between node 6 and the horse is 13, comparable to the 15 between node 6 and the carp.
All the changes in cytochrome c are neutral, so they continue to accumulate throughout time along each branch, resulting in the fact that none of the living forms at the ends of the branches are intermediate between any of the other living forms. The fact that most of the animals located above a node share the substitutions that occur below that node is strong evidence that those animals are descended from a common ancestor. In general, the closer two organisms are in the classification, the more substitutions they have in common, exactly what one would expect on the basis of evolution. On the other hand, because these substitutions are neutral, there is no possible reason why an intelligent designer should want to make such changes. Under the intelligent design hypothesis, all the cytochrome c proteins should be identical!
Pandas reveals the rationale of its design argument in these sections. Biochemical systems are composed of many interactive parts which have to operate simultaneously. Leaving out any component leaves the system inoperative. Thus it is impossible that they could have evolved in a step-wise fashion; they must have been created in their fully complex form by intelligent designer(s).
But there is something wrong with this argument. Let us apply it, as Pandas does, to an analogous system—the automobile. Modern cars are very complex pieces of machinery, with complex electrical systems, pollution controls, and computer control of many aspects of the engine's operation. Problems with any of these systems may render the car inoperative. They must all operate simultaneously. Therefore it follows that no simpler designs of cars are possible. The car that Henry Ford invented at the turn of the century must have had all these systems in their present degree of complexity. Of course, that is not true.
When a new component is added to a system, the old components which formerly worked by themselves in the old version of the system, have their interactions with the system modified and possible made dependent on the new component. The same could very well have happened in the evolution of the clotting system. Pandas "logical" argument for a designer is faulty.
Pandas' description of the blood clotting mechanism is so awkward and the accompanying figure (Figure 6-6) so poorly designed that the mechanism appears much more complicated than it really is. My Figure 6.2 emphasizes the sequential pattern of serum proteases that form a cascade and amplifying mechanism. Figure 6.3 contains a more modern and detailed presentation. Each of the active enzymes has a short mean life span, but as the enzymes in each stage produce a larger number in the following stage, one molecule of Hageman factor may result in thousands of molecules of fibrin being produced in a very short time. The system acts as an amplifier (McFarlane, 1964; Davie and Ratnoff, 1964). The figures also shows the factor numbers that have been used in place of names in the more recent literature. Thus Hageman factor is Factor XII, etc.
This cascade could easily have evolved from the bottom up, the insertion of each additional step enhancing the amplification and fine-tuning of regulation (Neurath, 1984). The greater blood pressures and activity of higher animals may have been the selective factor in increasing the haemostatic efficiency of this mechanism (McFarlane, 1964). Factors XII (Hageman factor), prekallikrein and HMWK (high molecular weight kininogen) at the upstream end of the intrinsic pathway can be defective and the clotting mechanism still works (Furie and Furie, 1988). Thus Pandas' statement "all of the proteins had to be present simultaneously for the blood clotting system to function" (top, column 1, p. 146) is wrong.
Figure 6.4 shows diagrammatically the various homologous domains these proteins share, indicating how they could have evolved via gene duplication, modification and exon shuffling (Furie and Furie, 1988). Based on these structures, Patthy (1985) has reconstructed their evolutionary history. The catalytic domain of the serum proteases is almost identical to that of the digestive proteases, such as trypsin. Their inhibitors also show striking homology to the inhibitors of the digestive proteases. These homologies suggest common ancestry for all these proteases (Neurath, 1984). This development of the clotting system from other preexisting proteins is a example of "tinkering" by natural selection, rather than the activity of a conscious, intelligent designer (Jacob, 1977).
Pandas cite Yockey (1977, not 1978!) as having published calculations on the origin by chance of a 100 amino acid protein. Actually, he considered cytochrome c with 101 amino acids and arrived at a probability of 2.1 x 10-65. This was done in the following manner: Given 20 different amino acids, and making certain allowances, there are 1.8067 x 10126 possible sequences of 101 amino acids. Based on the chemical similarity of various amino acids and hence the possibility of neutral substitutions, there are 3.8 x 1061 different cytochrome c sequences, or 3.8 X 1061/1.8067 x 10126 = 2.1 x 10-65 of the total (Yockey, 1977, pp. 386-387).
In a similar manner, Reidhaar-Olson and Sauer (1990, p. 315—Pandas' reference 5), on empirical grounds, estimated that there were 1057 functional sequences of a particular 92-residue domain, or 1 x 1057/4.9517 x 10119 = 2 x 10-63 of the total, a proportion similar to Yockey's.
On the other hand, Lau and Dill (1989, p. 3993—Pandas' reference 4), assuming there are only two kinds of amino acid residues (hydrophobic and polar), calculated the folding patterns for all possible sequences of 1024 residues. Six (5.86 x 10-03) had only 1 native state (folding pattern or conformation), which might confer a biological advantage compared to others that exhibited a number of conformations. They suggest that if there were 20 types of residues, there might be a larger population of sequences with only one or a few conformations.
Underlying these calculations is the assumption that, for example, the first cytochrome c had 101 positions and worked in same fashion as the cytochrome c of today. Maybe it was much simpler. An investigation of the family of calcium-binding proteins suggests that a modern protein with 160 amino acids originally only had 40 (Awbrey and Thwaites, 1981, p. 16). Fully a third of all proteins and enzymes are built around an inorganic metal atom-containing prosthetic group, such as the porphyrin ring found in cytochromes, hemoglobins, and chlorophyll. The prosthetic group can perform the function of the protein by itself. The protein simply fine tunes the action of the prosthetic group to make it more specific and efficient (Anon. 1980). Such proteins could have originated from very short amino acid chains that grew larger with time. Finally, there is evidence that many large proteins originated as many repetitions of short amino acid oligomeres (Ohno, 1981; Ohno and Epplen, 1993; Go, 1983). Such considerations make these Yockey-type calculations irrelevant!
The work done under the direction of Sauer has shown that the amino acid message "is highly degenerate in that many different sequences can code for proteins with essentially the same structure and activity." In other words "proteins are surprisingly tolerant of amino acid substitutions" (Bowie et al, 1990). "There is a wide range in tolerance to amino acid substitutions...The results reveal the high level of degeneracy in the information that specifies a particular protein fold." (Reidhaar-Olson and Sauer, 1990.) Bowie and Sauer (1989) describes the experimental technique used in these studies. This degeneracy would greatly facilitate the step-by-step evolution of proteins under the direction of natural selection. Thus we do not need to rely on an undirected search as Pandas assumes.
As the family of serum proteases illustrated, many proteins are derived from others by gene duplication, gene modification and exon shuffling (Blake, 1983; Doolittle, 1981; Furie and Furie, 1988; Neurath, 1984; Patthy, 1985). These mechanisms for evolving new genes and proteins from old are neglected by Pandas. Instead, they follow Ambrose and fall back upon supernatural events (see Pandas, Chapter 2). Totally different and unique proteins can arise through a frame-shift mutation. An actual example involves a new enzyme which arose around 1975 and allowed a microorganism Flavobacterium to break down the byproducts of nylon manufacture (Thwaites, 1985; Ohno, 1984; Okada et al, 1983). This event was made more likely by the fact that the original protein originated as a series of oligomeric repeats and retained a degree of internal repetitiousness (Ohno, 1984).
Again, Pandas' line of thinking (and its fallaciousness) can be illustrated by an analogy. Imagine that an exhaustive study restricted exclusively to the design, manufacture and operation of a modern jumbo jet concludes that such an airplane could only be made by a huge industrial complex. Furthermore, it is inconceivable that any airplane (past or present) could be simpler in design and still function, and certainly not so simple that it could be fabricated by two bicycle repairmen in the back of their shop! (If all the proteins must have originated in their modern forms, the original primordial cell must have had the complexity of a modern cell and there has been no evolution at the biochemical and intracellular level. Presumably Pandas believes there has been no ‘progressive creation' at these levels either.) The Wright brothers must have built a jumbo jet!
Pandas says, "Any view or theory of origins must be held in spite of unsolved problems; proponents of both design and unplanned descent acknowledge this." But there is a fundamental difference between these two views in regard to this point. Evolution is a theory of a specific natural mechanism. The theory not only recognizes its problems but specifies how they are to be solved, i.e. it serves as a guide to future research and has been extremely fruitful in serving this function. In contrast, the hypothesis of intelligent design simply postulates a totally mysterious, supernatural entity and provides no insight whatsoever as to how to solve its problems. (At various places in this book, Pandas says that intelligent design has its problems. But Pandas never says specifically what they are or how they are to be solved.)
Anon. 1980. The End of a Chemical Dichotomy. Mosaic 11(1): 23-28. (January/February.)
Awbrey, F. and W. Thwaites. 1981. Evolution vs. Creation. Aztec Lecture Notes. San Diego State University.
Blake, C. 1983. Exons—present from the beginning? Nature 306: 535-537.
Bowie, J. U., J. F. Reidhaar-Olson, W. A. Lim and R. T. Sauer. 1990. Deciphering the Message in Protein Sequences: Tolerance to Amino Acid Substitutions. Science 247: 1306-1310. (16 March.)
Bowie, J. U. and R. T. Sauer. 1989. Identifying determinants of folding and activity for a protein of unknown structure. Proceedings of the National Academy of Science USA. 86(7): 2152-2156. (April).
Doolittle, R. F. 1981. Similar Amino Acid Sequences: Chance of Common Ancestry? Science 214: 149-159.
Davie, E. W. and O. D. Ratnoff. 1964. Waterfall Sequence for Intrinsic Blood Clotting. Science 145: 1310-1312. (18 September).
Dayhoff, M. O., C. M. Park and P. J. McLaughlin. Building a Phylogenetic Tree: Cytochrome C. In: M. O. Dayhoff (Editor) 1972. Atlas of Protein Sequence and Structure 1972. Silver Spring, MD: National Biomedical Foundation. volume 5, pp.7-16.
Furie, B. and B. C. Furie. 1988. The Molecular Basis of Blood Coagulation. Cell, 53(4): 505-518 (May 20.)
Go, M. 1983. Modular structural units, exons, and function in chicken lysozyme. Proceedings of the National Academy of Sciences USA. 80(7): 1964-1968. (April.)
Jacob, F. 1977. Evolution and Tinkering. Science 196: 1161-1166. (10 June).
Lau, K. and K. A. Dill. 1989. A Lattice Statistical Mechanics Model of the Conformational and Sequence Spaces of Proteins. Macromolecules. 22: 3986-3997.
McFarlane, R. G. 1964. An Enzyme Cascade in the Blood Clotting Mechanism, and its Function as a Biochemical Amplifier. Nature 202: 498-499. (May 2).
Neurath, H. Evolution of Proteolytic Enzymes. Science 224: 350-357. (27 April).
Ohno, S. 1981. Original domain for the serum albumin family arose from repeated sequences. Proceedings of the National Academy of Sciences USA. 78(12): 7657-7661. (December.)
Ohno, S. 1984. Birth , of a unique enzyme from an altern, ative, reading frame of the preexisted internally repetitio, us coding sequence. Proceedings of the National Academy of Sciences USA. 81(8): 2421-2425. (April.)
Ohno, S. and J. T. Epplen. 1993. The primitive code and repeats of base oligomers as the primordial protein-encoding sequence. Proceedings of the National Academy of Sciences USA. n80(11): 3391-3395. (June.)
Okada, H. S. Negoro, H. Kimura and S. Nakamura. 1983. Evolutionary adaptation of plasmid-encoded enzymes for degrading nylon oligomers. Nature 306: 203-206.
Patthy, L. 1985. Evolution of the Proteases of Blood Coagulation and Fibrinolysis by Assembly from Modules. Cell 41: 657-663. (July).0
Reidhaar-Olson, J. F. and R. T. Sauer. 1990. Functionally Acceptable Substitutions in Two alpha-Helical Regions of Lambda Repressor. Proteins: Structure, Function, and Genetics. 7: 306-316.
Thwaites, W. M. 1985. New Proteins Without God's Help. Creation/Evolution 5(2): 1-3.
Yockey, H. P. 1977. A Calculation of the Probability of Spontaneous Biogenesis by Information Theory. Journal of Theoretical Biology. 67: 377-398.
(from Frank Sonleitner's critique of Of Pandas and People)
This replaces the section "A Word to the Teacher" written by the "Academic Editor" Charles B. Thaxton, that appeared in the 1st edition. The present section, written by Mark D. Hartwig and Stephen C Meyer, tries to make the same points that Thaxton did, namely, that somehow the concept of a supernatural creator is scientific!
Hartwig and Meyer say that Stephen Gould pronounced the neo-Darwinian synthesis effectively dead. Actually Gould (Gould, 1980, p. 120) stated that only a particular version of the synthetic theory, based on a 1963 quote of Ernst Mayr, was effectively dead. Surely Gould would not have said that about a later version (Mayr, 1967) which included, as a central tenet, Mayr's peripatric speciation (which later became Gould's punctuated Equilibrium!) Also, Gould is a champion of Darwin, of natural selection, "the pearl of great price" at the center of Darwinism, and the creativity of natural selection (Gould, 1976).
Teaching about alternative explanations and controversies in science certainly has pedagogical value. Unfortunately Pandas advocates a nonscientific alternative which it supports by distortions, errors and untruths about the evidence and about the theory of evolution.
This section is organized after Thomson (1982) who indicated that there were three meanings for the word evolution.
The first meaning is "change over time" and is based on the fact that there are sequences of fossils in the geologic strata. Hence the kinds of organisms present on earth have changed over time in a general progression where, as time passes, the forms become more like those existing today. This is based on the assumption that the various geologic strata were laid down in a time sequence extending far back into the history of the earth. Almost everyone accepts this: evolutionists (Darwinian, non-Darwinian and theistic), and all progressive creationists, including Pandas. The only people who reject it are the 6 day (young earth) creationists, who claim that all the geologic strata were laid down during the one year of Noah's Flood.
The second meaning that "all organisms are related by descent through common ancestry" is based on the law that "all life comes from life" a principle based on our knowledge of the present. Hence organisms that formed fossils in younger strata must be descendants of organisms that formed fossils in the older strata. This is accepted as a fact by all evolutionists and most progressive creationists. Ambrose (1982), who realizes that the supernatural provides no understanding, tries to minimize it in his hypothesis of progressive creation. Thus he envisions a continuity of descent, new forms arising though speciation by punctuated evolution but with the designer modifying the DNA (Ambrose, 1982, pp. 143, 161, 164.) Pandas apparently believe that the designer made each successive form anew although it might have made use of the blueprints of previous organisms (Pandas, p. 42.) Thus Pandas is rejecting the law that "all life comes from life." Clearly this is all sheer speculation about the supernatural which we shall never be able to investigate, test, or understand.
The third meaning refers to the "explanatory mechanism" of evolution. The Darwinian mechanism (mutation, genetic recombination, reproduction, and natural selection) can be studied in nature and in the laboratory at the present time in a fashion typical of an inductive or theoretical science. Does our evidence of the nature of past life correspond to what we would expect on the basis of Darwinism? Whenever that evidence has been sufficiently detailed, the answer is: yes! The explanation is still strictly theoretical because we cannot actually observe this mechanism operating in the past. This theory is accepted by Darwinian evolutionists and some theistic evolutionists. It also is accepted by most non-Darwinians evolutionists and progressive creationists for microevolution. Non-Darwinian evolutionists postulate other mechanisms for macroevolution, but so far none have been proposed that have any scientific validity.
On the other hand, Pandas claims that "a growing minority of scientists" see intelligent design "as a plausible alternative..." to Darwinism. This comes from Thaxton, Bradley and Olsen (1984, pp. 203-212). But since we know nothing about the nature of these designers, have never had any experience with such supernatural entities and can never hope to have any, how can we know that this idea is plausible? What do we have to compare it with? Plausibility has no meaning in regard to the supernatural!
Pandas still doesn't realize that the intelligent design explanations of science involve natural designers. Humans are natural entities whose functioning obeys natural laws. Thus anthropologists may study and try to reinvent the techniques of stone tool making as practiced by ancient hominids (Howell et al, 1965, pp. 110-113).
All scientific explanations of specific phenomena involve the application of laws and theories to specific conditions (see the supplement on Science.) Such instance usually involve discovering and testing the specific conditions that predict the observations. In this sense the theoretical and historical sciences (to use Popper's terms (Popper, 1957) are the same. They differ only in that the historical sciences are concerned almost exclusively with explaining specific instances while the theoretical sciences also test general laws and theories. The testing of general laws and theories also must be done with respect to specific instances, but usually takes the specific conditions as given.
The historical sciences seek to understand how things came to be by applying the laws and theories (natural mechanisms) of the present world, as discovered by the inductive (theoretical) sciences, to the past. The Darwinian mechanism (the interplay of mutation, genetic recombination, reproduction and natural selection) can be studied in the present day by the theoretical sciences and applied to the past, to explain the arrays of fossils and various features of anatomy, physiology, development, etc. of present day organisms. The process is completely analogous to a forensic scientist trying to reconstruct a murder (the specific conditions) which, in conjunction with known scientific laws and theories, will explain the evidence gathered from the corpse and the crime scene. Postulating a supernatural demon that struck down the victim through some sort of "spell" would be laughed out of court. Postulating supernatural intelligent intervention is completely inappropriate in any science, inductive or historical!
All scientific theories entail mechanisms that feature unobservable entities: atoms, electrons, all the elementary particles of physics, electromagnetic fields, etc. But all these entities are assigned specific properties which allow the scientist to make predictions that can be tested. The invisible and supernatural intelligent designer exists only as a simple, amorphous idea from which no logical predictions can be deduced.
Intelligent design assumes an intelligent designer (i.e. creator) or designers (creators) who are beyond scientific study. We cannot study any present day activities of such designers to learn anything about their properties. In fact there are no present day observations that require the designers to be at work at the present time. Not knowing anything about the intelligent designers, the intelligent design advocate cannot produce any specific observable consequences (predictions) of their hypothesis which would allow it to be tested. All such "predictions" of intelligent design advocates (or creationists) are simply ad hoc statements which might falsify evolution if true. Take for example, the assertion (p. 160) that: "the concept of intelligent design predicts that complex information, such as that encoded in a functioning genome, never arises from purely chemical or physical antecedents."
From what basic postulates of the intelligent design hypothesis and by what deductive steps is this statement derived? The answer is not to be found in Pandas. And exactly what does "arises from purely chemical or physical antecedents" mean? Does the Darwinian mechanism fall under this rubric? Clearly the Darwinian mechanism is a purely natural (as opposed to supernatural) process. Certainly new genes are duplications of old genes (arising by well-understood genetic processes) that have become different through the Darwinian mechanism. This certainly happens in microevolution, which Pandas accepts! It would falsify the prediction. Yet it obviously it doesn't conflict with the idea of intelligent designers as far as Pandas is concerned. Pandas simply denies that microevolutionary changes can be extrapolated into macroevolutionary changes.
As another example of an ad hoc prediction, Pandas would claim that the intelligent design hypothesis predicts that transition forms did not exist and will not be found, but Ambrose' version would predict that such forms did exist.
The people who adamantly insist on teaching "intelligent design" in science classes are the young earth creationists, who will identify it with fundamentalist religion! As I have shown, the supernatural design hypothesis makes no contribution to science. In scientific terms it is equivalent to "we don't know." Because it makes no logically justifiable predictions, its only possible empirical support is negative. If our scientific theories fail, one can always give up and say "we don't know." At present Darwinism is the only scientific theory of biological origins (Denton, 1985, p. 355.)
The intelligent design hypothesis actually denies the principle of uniformity (Pandas, pp. 56, 64) and the law that "life comes from life" (Pandas, pp. 42-43)! In the past supernatural creators made living things. They are no longer doing so. Today all living things come from previously living things. True, scientists claim that at one time in the remote past, the earliest life developed from nonliving sources, but this came about through natural physical and chemical processes that can be investigated in the present day.
Ambrose, E. J. 1982. The Nature and Origin of the Biological World. Halsted Press. New York.
Denton, M. 1986. Evolution: A Theory in Crisis. Adler and Adler. Bethesda, Maryland.
Gould, S. J. 1976. Darwin's Untimely Burial. Natural History LXXXV(8): 24-30. (October).
Gould, S. J. 1980. Is a new and general theory of evolution emerging? Paleobiology 6(1): 119-130.
Howell, F. C. and the Editors of LIFE. 1965. Early Man. Time Inc. New York.
Mayr, E. 1967. Evolutionary Challenges to the Mathematical Interpretation of Evolution. In: P. Moorehead and M. M. Kaplan (editors). Mathematical Challenges to the Neo-Darwinian Interpretation of Evolution. Philadelphia: Wistar Institute Press, pp. 47-58.
Popper, K. R. 1957. The Poverty of Historicism. Boston. The Beacon Press.
Thaxton, C. B., W. L. Bradley and R. L. Olsen. 1984. The Mystery of Life's Origin: Reassessing Current Theories. Philosophical Library Publishers. New York.
Thomson, K. S. 1982. Marginalia: The meanings of evolution. American Scientist 70(5): 529-531 (September-October).
(from Frank Sonleitner's critique of Of Pandas and People)
The purpose of the brief descriptions given below are to give a summary of the authors' position in the Creation/Evolution controversy and are not intended to be exhaustive reviews of the various works.
Thaxton, C. B., W. L. Bradley and R. L. Olsen. 1984. The Mystery of Life's Origin: Reassessing Current Theories. Philosophical Library Publishers. New York.
The three authors are a chemist, materials scientist and a geochemist respectively. Thaxton was involved in the production of Pandas and wrote the section "A Word to the Teacher" found in the 1st Edition. One of the authors of Pandas, Dean Kenyon, wrote the foreword to this book. The authors accept the validity of an old earth (pp. 70-73) and presumably the sequence of life forms documented in the fossil record.
This book forms the basis for much of Excursion chapter 1 and the corresponding part of the overview chapter and Pandas' justification for including supernatural intelligence in science. It contains a detailed and critical review of prebiotic or chemical evolution in a manner somewhat similar to Shapiro (see below). Only two points will be considered here. The first is that, in their discussion of thermodynamics, the authors do distinguish two entropies, the thermal entropy and the configurational entropy (p. 132). They apparently confuse complexity with order and thus, in contrast to Yockey (see below), they claim that the configurational entropy decreases as organisms get more complex.
The second point concerns the nature of the primitive atmosphere. The authors admit that there is wide agreement that the primitive atmosphere was neutral consisting of CO2, N2, and maybe H2. Two of the three lines of evidence the authors claim indicate O2 in the primitive atmosphere involve sediments younger than the origin of life and hence irrelevant. The third is the photodissociation of water in the upper atmosphere. The most they say about this is that it is "suggestive" (pp. 93-94).
In the Epilogue the authors introduce their distinction between operations science and origins science. Origins science deals with singular events and its theories cannot be falsified. Instead origins theories are to be tested as to whether they are plausible or not. This different criterion makes miracles and the supernatural valid explanations! Thus the authors contend that it is scientific to evaluate the plausibility of Special Creation. They do not elaborate further upon the concept of Special Creation.
Here it should also be pointed out the Popper said that hypotheses in both the theoretical and historical sciences are testable and falsifiable (Popper 1957, p. 143 fol.) Paradoxically, creationists have always claimed that they have disproved (falsified) evolution. As for the criterion of plausibility, we can evaluate the plausibility of a naturalistic origin-of-life scenario by comparing it with our empirically derived knowledge of physics, chemistry and geology (and, in fact, if it contradicts the laws of those fields, it is falsified!) but we have no corresponding knowledge (empirical or otherwise) of the creative abilities of supernatural intelligences so how, in the latter case, can we tell what is plausible and what is not?
Popper, K. R. 1957. The Poverty of Historicism. Boston. The Beacon Press.
Shapiro, R. 1986. Origins: A Skeptic's Guide to the Creation of Life on Earth. Summit Books, New York. (and W. Heinemann Ltd., London)
This book is similar to Thaxton et al in that it presents a skeptical treatment of the various scenarios of prebiotic research but it is written more for the general public. It includes background material on the nature of science, biochemistry, geological evidence for an old earth and the earliest living things. Although Shapiro, a biochemist, feels that, although so far prebiotic research has not been very successful, "the scientific options are far from exhausted" and "we may yet penetrate the mystery." (p. 298). Shapiro himself speculates that proteins may have come first followed later by RNA and DNA and that we may find clues to the answer in more elaborate and accurate prebiotic simulation experiments and investigation of other places in the solar system such as the moons Titan and Europa where prebiotic syntheses may still be occurring. He has a chapter on the modern creationist movement which he rejects as not being scientific.
Yockey, H. P. 1992. Information Theory and Molecular Biology. Cambridge University Press, Cambridge.
On p. 76 of the 1st Edition of Pandas, the authors gave a reference to: The Mathematical Foundations of Molecular Biology, by Hubert P. Yockey. New York: Cambridge University Press, 1989 which turned out to be a nonexistent book that had not yet been published. In the 2nd Edition, they give a reference to the same book but with a publication date of 1992. This book does now exist, but never being content with getting things right, Pandas neglect to inform the reader that the title has been changed to "Information Theory and Molecular Biology"!
Yockey is an evolutionist and although he, like Shapiro (see above), is very skeptical about modern day scenarios about the origin of life and thus would qualify to be listed at the end of Excursion Chapter 1, nothing he says in his book supports what Pandas says about information theory and evolution in Excursion Chapter 2! It would appear that Kenyon and Davis have never read this book.
Yockey's book is very useful for the evolutionist. He discusses neutral mutations in cytochrome c, the origin of new genes by duplication of old ones, molecular clocks, and proves quite conclusively that evolution has nothing to do with the second law of thermodynamics.
With regard to that last point, Yockey's chapter 12 should be required reading for every creationist. The Maxwell-Boltzmann-Gibbs entropy is a measure of the ‘orderliness' of energy in a system which is addressed by the second law of thermodynamics. The amount of information in a DNA molecule, on the other hand, is measured by the Shannon or Kolmogorov-Chaitin algorithmic entropy, and as evolution proceeds and organisms become more complex, not more orderly, the Shannon entropy increases. In addition the Shannon entropy and Maxwell-Boltzman-Gibbs entropy are based on probability spaces that are not isomorphic to each other. Hence they have nothing to do with each other and "thermodynamics has nothing to do with Darwin's theory of evolution." (p. 313).
Ambrose, E. J. 1982. The Nature and Origin of the Biological World. Halsted Press. New York.
Ambrose accepts the Big Bang (p. 168), that the earth is very old (pp. 19-20, 101), in the gradual development of life in the early Precambrian possibly on montmorilite clays (p. 133), in conventional historical geology and fossil sequences (pp. 100-103), and the origin of humans from apes (pp. 156-157). He appears to accept the theory of punctuated equilibrium (pp. 118-119, 143) with this modification: during a speciation event, a creative intelligence manipulates the organism's DNA, adding new genetic information (pp. 131, 137, 143), thus creating new organisms from old ones (p. 164). He is more of a ‘progressive creationist' than a ‘theistic evolutionist.' He realizes that appealing to a supernatural creator is basically meaningless as an explanation (p. 161) and suggests that the creator's mind acts by affecting the quantum indeterminacy at the subatomic level (p. 164, 168). Thus he accepts the picture of the origin and nature of the universe as developed by science with the exception that he envisions evolution by a creator's ‘genetic engineering.' Although he is a Christian, he states that "the first chapters of the book of Genesis do not present a biological or anthropological account of the creation of the biological world and the making of mankind,..."
Johnson, P. E. 1991. Darwin on Trial. Regency Gateway, Washington, D. C.
This book is very similar to one written by another Harvard graduate, Norman Macbeth, who wrote "Darwin Retried: An appeal to reason" (Gambit Inc. Boston 1971.) Both authors accept evolution, the change in organic forms over geologic time, but attack a particular proposed mechanism, Darwinism, i.e. mutation and natural selection. To this extent, the book is also similar to Ambrose, Lovtrup, Augros and Stanciu and, to a lesser extent, to Denton (which Johnson has read—see p. 36). Thus in chapters 2 and 3 he attacks two facets of the Darwinian mechanism: natural selection and mutation. Yet in subsequent chapters (exp. 4, 5, 11, 12) he tends to conflate the phenomenon of evolution and the Darwinian mechanism and begins to sound much more like Denton (see below). He even questions evolution itself on p. 62. And on pp. 12-13, he questions whether the "fact of evolution" can be separated from its mechanism and whether this "fact" has any content without a mechanism.
He discusses the creation/evolution controversy in chapters 1, 11, and 12 and gives his own views on the subject on pp. 3-4, 14 and 113. Thus he says:
"The concept of creation in itself does not imply opposition to evolution, if evolution means only a gradual process by which one kind of living creature changes into something different. A Creator might well have employed such a gradual process as a means of creation. "Evolution" contradicts "creation" only when it is explicitly or tacitly defined as fully naturalistic evolution—meaning evolution that is not directed by any purposeful intelligence."
"Similarly "creation" contradicts evolution only when it means sudden creation, rather than creation by progressive development."
On p. 14 he says:
"I am a philosophical theist and a Christian. I believe that a God exists who could create out of nothing if He wanted to do so, but who might have chosen to work through a natural evolutionary process instead. I am not a defender of creation-science..."
But it can't be a totally natural evolutionary process (p. 4, 113), because, in his opinion, that would be "naturalism" (pp. 114 fol.) a philosophy that banishes God from any influence in the universe! (And he strongly criticizes evolutionists for teaching this atheistic philosophy in the schools—see chapters 11, 12). He also appears to be aware that the alternative to "natural" is "supernatural" the latter term meaning inaccessible to human understanding (p. 28) and inaccessible to scientific investigation (p. 33). If science is to have a successful theory, i.e. one that explains a set of phenomena, it must be naturalistic. Thus Johnson is faulting Darwinism for claiming that it can explain evolution! He apparently would prefer that scientists say that they can't explain evolution. But if they can't, then maybe it doesn't exist! (pp. 12-13, 62). Perhaps he would be content if they claim to only explain 95% of evolution, leaving the other 5% unexplained and open to supernatural speculation. His position rests on the metaphysical assumption that anything God does must be supernatural! But even if this be so, Darwinism doesn't completely banish God from the evolutionary process. Mutations are said to occur at random, which means we can't pinpoint the exact factors that produce them in any given instance, and that leaves room for a theistic evolutionist to postulate that God is responsible for at least some of them.
An annoying tendency of the author that becomes clear in reading this book is that with regard to any question, he wants to be on both sides at once! Thus Johnson will attack a scientific theory if he thinks it is not successful in explaining the phenomena, but if it is successful he will still attack it because now it banishes God from that aspect of the universe. Science can't win. This law professor is just too clever!
Lovtrup, S. 1987. Darwinism: The Refutation of a Myth. Methuen, New York. (also Croom Helm, London)
This book is mainly an historical review of the development of evolutionary thought. Lovtrup is an evolutionist. He states that the occurrence of evolution over geological time is "one of the best substantiated theories in biology" but he makes a number of theoretical and empirical biological mistakes which lead him to evolution by macromutations, ala Goldschmidt and Schindewolf. Lovtrup mentions Denton's book (p. 367) favorably but, of course, does not agree with that author's "refutation" of macromutation theory!
Augros, R. and G. Stanciu. 1987. Shambhala, Boston.
These authors accept the picture of origins developed by science: the Big Bang (p. 222), the old age of the earth and the succession of forms in the fossil record (p. 220) and the fact(!) of evolution (p. 186 fol.) They, however, reject the Darwinian mechanism totally, arguing that natural selection doesn't work and that Darwin's basic premises are incorrect (p. 160). Thus they argue against exponential growth (p. 125), and the struggle for existence (chapters 4 and 5); predation and parasitism are totally benign phenomena (p. 101-104). The authors' ‘New Synthesis' states that evolution results from an internal genetic process reorganizing superfluous DNA and changing regulatory genes to produce a new species; an idea similar to the Lamarckian innate tendency of organisms to climb the ladder of complexity. These events occur during a round of punctuated equilibrium (pp. 181-183). It was the mind of God that originally shaped matter into organic forms (p. 191). The Creation/Evolution controversy arises because both evolutionists and creationists conflate evolution with Darwinism (p. 228). Evolution is true but the Darwinian mechanism is not.
Denton, M. 1986. Evolution: A Theory in Crisis. Adler and Adler, Bethesda, Maryland.
Denton appears to accept the old age of the earth and the successive appearances of fossils. He accepts microevolution and speciation by Darwinian evolution without reservation (Chapter 4, p. 344). In this regard he is in conflict with Pandas' chapter 3. He believes that macroevolution doesn't occur, although, amazingly enough, he accepts the evolution of horses from Eohippus (p. 93) which, even more amazingly, he claims is an exception that proves the rule! (p. 185)
Denton claims to have held both placental dog and marsupial thylacine skulls and claims that they are so much alike that only a skilled zoologist could distinguish them (p. 178), a "fact" that Pandas makes much of in their chapter 5. In actuality the differences are so clear cut and obvious that a small child would have no difficulty in distinguishing them causing one to wonder about Denton's powers of observation.
There are two main points that Denton makes. One is his claim that life is a fundamentally discontinuous phenomenon (Chapters 5, 6, p. 353). Denton wishes to return to the typological biology of the 19th century as exemplified by the hierarchic classification. He is unaware that many fossils blur the clear-cut distinctions found in living forms. Even Richard Owen thought the fossil Archegosaurus was a link between fish and reptiles, erasing the boundaries between those two classes and accepted the idea of fossil continuity. Owen also thought that the mammal-like reptiles filled the gap between reptiles and mammals. He envisioned a process of "continuous creation" which amounted to evolution with a supernatural mechanism. (Desmond, 1982, pp. 68, 71, 72, 82, 198).
Denton also seems to be unaware of the fact that the typological hierarchic classification rested extensively on the concept of homology. Denton sees homology as a purely evolutionary concept and doesn't realize, that in rejecting it (Chapter 7) he is rejecting the basis of his typological biology! (Denton's chapter 7 is the basis for Pandas' chapter 5. His discussion of cytochrome c in Chapter 12 is the basis of Pandas' Chapter 6, especially in the 1st edition of Pandas.)
His second point is that Darwinism is evolution by pure chance and that such a process could not possibly have resulted in complex organisms. This seems to stem from his inability to comprehend the concept of natural selection. Although on occasion he mentions Darwinian evolution as being guided or directed by natural selection (pp. 85, 154, 260, 271, 341), he more often describes evolution as being "an entirely blind random process" (p. 43, 53, 66, 134, 345), "a gigantic random search" (61, 348), "undirected process of change" (p. 136) "pure chance" (p. 311, 317, 323, 324, 326, 327, 331, 351, 352, 357), "unguided trial and error" (p. 314). He even seems to equate natural selection with blind chance (p. 60, 317). He rejects the idea that a complex adaptation might evolve slowly, being guided by natural selection at each step (pp. 317-319) but instead envisions an adaptation coming into full blossom purely by chance and only then being subsequently preserved by natural selection (pp. 61, 327) but he is not even sure of that (p. 135)! Even in his discussion of how mutational changes may spread (p. 60) he describes how the rate of change depends on factors such as mutation rate, generation time and total population number but natural selection (differential survival and reproduction) is omitted!
In spite of all this, Denton claims that Darwinism is the "only truly scientific theory of evolution" while creationist theories "invoke frankly supernatural causes" (p. 355). Because he rejects Darwinism, and since there is no alternate scientific theory (p. 357), and supernatural causes are apparently not satisfactory, he concludes that we do not know how new forms arise (p. 358).
Desmond, A. 1982. Archetypes and Ancestors: Palaeontology in Victorian London 1850-1875. University of Chicago Press. Chicago.
(from Frank Sonleitner's critique of Of Pandas and People)
Mutations in homeotic genes cause the replacement of one body structure by another normally located elsewhere (homoeosis: Bateson, 1894, pp. 84-85). Such body structures are usually serially homologous. Serial homology is a feature of metameric (segmented animals) where structures such as legs, nerve ganglia, spiracles, blood vessels, etc. occur in each segment. Thus the legs of a centipede are serial homologous to each other and to the mouthparts (mandibles, first and second maxillae) which have evolved from legs. Homeotic genes were first discovered in Drosophila—the Antennapedia complex and the Bithorax complex (ANT-C and BX-C) which control the anterior-posterior differentiation of the front half (head to second thoracic segment) and rear half (third thoracic segment to end of abdomen) of the body respectively (Lewis, 1963; Lewis, 1978; Kaufman, Lewis and Wakimoto, 1980) As examples of homeotic changes, a mutant of Antennapedia converts the Drosophila antenna to a thoracic leg; bithorax mutations convert the fly's halteres into a second pair of wings. Other examples are given by Raff and Kaufman (1983, chapter 8.)
These complexes of homeotic genes have two interesting features. One is that the physical order of the genes in a complex is identical to the order in which the genes are expressed along the anteroposterior axis of the embryo during development. The domains of expression along this axis correspond to the segments that are affected by mutations in these genes. Thus there is a colinear sequence between the genes on the chromosome and the structures along the anterior-posterior axis of the body that they affect (Graham, Papalopulu and Krumlauf, 1989.)
Secondly, it has recently been discovered that each gene in these complexes contains a highly conserved subsequence of 183 base pairs encoding for a DNA-binding domain of 61 amino acids called a homeobox (McGinnis, Levine, Hafen, Kuroiwa and Gehring, 1984; Riddihough, 1992a.) This finding proved to be a ‘rosetta stone' for finding pattern formation genes (Gehring, 1985; Maddox, 1984; Struhl, 1984; Slack, 1984.) Modern molecular genetics techniques could readily find genes containing the homeobox sequence and complexes of homeobox genes nearly identical to those found in Drosophila were subsequently found in a wide variety of animals including the mouse and the human! (McGinnis, Hart, Gehring and Ruddle, 1984; Levine Rubin and Tjian, 1984; Kessel and Gruss, 1990.)
Vertebrates are metameric animals to a certain extent, their metameres including vertebrae, ribs, nerve cord ganglia, somatic muscle bundles, etc. The homeotic genes in the mouse, called Hox genes, perform the same function as those in Drosophila, i.e. controlling the anterior-posterior differentiation of the animal. The overlapping regions of expression of the various Hox genes along the anterior-posterior axis may form a code (Figure 1) that determines which target genes are to be activated (Gould, 1991; Riddihough, 1992b) The first metameric structures found to be controlled by these genes were the rhombomeres of the hind brain and associated branchial structures (Hunt et al, 1991; Simeone et al, 1992.)
The fact that body plans as diverse as a fruit fly and a mouse should be determined by an almost identical underlying system of regulatory genes was an entirely unexpected discovery! Some vertebrate homeobox genes are structurally so similar to those in Drosophila that they can function in the fruitfly (Akam, 1989, 1991.) The mouse Hox-2.2 gene, virtually identical in its DNA sequence to the Drosophila Antennapedia (Antp) gene, induces transformations nearly identical to those of Antp, i.e. thoracic denticle belts in place of head structures and thoracic legs in place of antennae when introduced into Drosophila (Malicki, Schughart and McGinnis, 1990.) Similarly the human HOX-4.2 gene, structurally similar to the Drosophila Deformed (Dfd) gene can mimic the function of the latter in Drosophila (McGinnis, Kuziora and McGinnis, 1990; Malicki et al, 1992.) And the Deformed gene has the same effect in mice as the homologous mouse Hox gene (Awgulewitsch and Jacobs, 1992.)
Comparative analysis indicates the subdivision of the Antennapedia-type homeobox genes into three classes early in metazoan evolution. Subsequent duplication generated a cluster of at least five genes in the common ancestor of insects and vertebrates eventually resulting in eleven of these genes in Drosophila (Schubert, Nieselt-Struwe and Gruss, 1993; Hoey, et al, 1986). Although the homeotic genes form two complexes in Drosophila, this is probably a peculiarity of dipterans. They exist in a single sequence (HOM-C) in other insects, such as the red flour beetle, Tribolium (Beeman, 1987; Stuart et al, 1991; Beeman et al, 1993.)
In vertebrates, tandem duplication, resulting in up to 13 linked genes, followed by duplication of these clusters occurred; each cluster later acquiring different secondary expression domains (Condie and Capecchi, 1994) allowing for the evolution of the more complex vertebrate body (Kappen, Schugart and Ruddle, 1989; Gaunt, 1991; Krumlauf, 1992; Holland, 1993; Pendleton, et al, 1993). Thus vertebrates, such as the mouse and human, have four Hox complexes. The corresponding genes in the complexes, identified by nucleotide sequence and their position in the Hox sequence, are paralogous and form a family. For example, Hox A3, B3 and D3 genes form a family (Figure 2.) There are 13 such families. Not all have members in all four complexes. The members of some families have identical function, while in other families the members have divergent functions.
The cephalochordate Amphioxus has only one complex. Amphioxus has only a small anterior swelling of the nerve cord, the cerebral vesicle, which passes for a brain (Garcia-Fernandez and Holland, 1994). Comparison of the anterior expression boundaries of mouse and amphioxus Hox genes suggests that the vertebrate brain is homologous to an extensive region of the amphioxus nerve cord containing the cerebral vesicle and extending posteriorly to somite four (Holland et al, 1992.)
Initially the four vertebrate Hox clusters were designated 1-4 and the genes within each were assigned numbers in the order in which the genes were discovered. This system was unsatisfactory because it obscured the homologies between genes in the different clusters and between genes in different animals. In 1992 the nomenclature was revised. The four clusters were redesignated A-D and the genes within each cluster numbered according to their anterior-posterior sequence (Scott, 1992.) The new and old names for the genes are shown in Figure 2.
In the past ten years, a great deal of research has elucidated the functioning of many of the 38 homeotic genes found in the mouse. Some of these results are summarized below:
The Hox A, C and D clusters are expressed in the limb buds. Those of the C cluster expressed in each limb (fore and hind) are different and are those expressed in the adjacent body mesoderm. Those of the A and D clusters are the same in each limb and are those expressed in the posterior body mesoderm (Figure 3.) In fishes and in the earliest tetrapods the pectoral and pelvic limbs are different in form. It has been suggested that early in the evolution of the tetrapods, the Hox A and D genes that controlled hind limb formation were co-opted for use in specifying pectoral fin pattern, resulting in the great similarity of the front and hind limbs in all later tetrapods (Tabin and Laufer, 1993; Coates et al, 1993.)
The Hox A and D genes appear to control the differentiation of the limbs along the anterior-posterior axis and partly along the proximal-distal axis (Dolle et al, 1989; Izpisua-Belmonte et al, 1991; Duboule, 1992; Morgan et al, 1992; Dolle et al, 1993.) There being only five distinct Hox-encoded domains across the limb bud, only five different types of digits can be formed, resulting in the basic pentadactyl limb. Although polydactyly, resulting in more than 5 digits is common, the extra digits are always duplicates of an adjacent digit (Tabin, 1992.)
Homeobox genes are implicated in feather development in birds. Microgradients in Hox proteins occur within a single feather; macrogradients occur across feather tracts. Doses of retinoic acid, a suspected morphogen, cause transformations between feather and scale (Chuong, 1993). Retinoic Acid interferes with the normal establishment of Hox codes (Boncinelli et al, 1991; Kessel and Gruss, 1991; Marshall et al, 1994.)
Slight modifications of the homeotic genes in Drosophila can cause changes in the body organization mimicking the fruit fly's ancient ancestors. The absence of the bithorax gene produces the more primitive four-winged condition. The absence of the Antennapedia gene produces a thorax with three similar nonwing-bearing segments, mimicking the apterygote condition. If the entire BX-C sequence is missing, the posterior end of the embryo develops as a series of similar trunk segments reminiscent of trignathous myriapods. If both the ANT-C and BX-C complexes are missing, an embryo with three head segments and a series of trunk segments is produced resembling the onychophoran condition (Raff and Kaufman, 1983, p. 259.) Of course, only the pattern of segment identity has changed. The target genes controlled by the homeotic genes still produce Drosophila-like structures and, in fact, such mutant changes as described above are eventually lethal to the developing embryo.
The wing-bearing segments have two types of appendages: wings and legs. In the developing larva, the wing imaginal discs originate from the dorsal region of the leg discs. The primitive appendage of the arthropods was branched, the dorsal part forming a gill and the ventral part, the leg proper. This, along with paleontological evidence, suggests that wings evolved from the gills of primitive aquatic insects (Williams and Carroll, 1993.)
Geneticists have searched everywhere for homeobox genes. They were found by McGinnis (1985) in Annelida (earthworm, leech), Arthropoda (shrimp, beetle, fly), Echinodermata (sea urchin), Urochordata (tunicate), Cephalochordata (Amphioxus), and Vertebrata (frog, chicken, mouse, human); by Holland and Hogan (1986) in Platyhelminthes (tapeworm), Brachiopoda, Nemertea, Mollusca (snail, sea hare), Echinodermata (starfish, sea urchin), and Chordate (mouse) and by Murtha, Leckman and Ruddle (1991) in mouse, fruit fly, swordtail fish, lamprey, ascidian, sea urchin, gastropod, hydrozoan, and hydroid. A homeobox gene has been found in the leech (Wysocka-Diller et al, 1989), in the nematode Caenorhabditis elegans (Kenyon and Wang, 1991; Cowing and Kenyon, 1992; Burglin et al, 1989) and the clawed frog, Xenopus (Carrasco et al, 1984.) The Knotted gene in maize was found to be a homeobox gene (Rennie, 1991) and homeo domains have been found in the alpha 1 and 2 mating type genes in yeast (Shepherd et al, 1984.)
Because of the ubiquity of homeotic clusters in animals, it has been suggested that the Hox system be adopted as the defining character of the kingdom Animalia and called the Zootype (Slack, Holland and Graham, 1993.) (The homeobox genes of plants, fungi and slime moulds do not fall in the homologous families of the genes comprising the zootype.) The extensive gene homologies in vertebrates and arthropods have prompted some authorities to revive the idea that a vertebrate is an upside-down version of an arthropod (Arendt and Nubler-Jung, 1994.)
The homeotic genes we have been discussing are homeotic selector genes. In Drosophila there are other groups of pattern forming genes: the homeotic regulatory genes, which insure the correct spatial expression of the homeotic selector genes, and segmentation genes, which control the number and polarity of body segments in the fly (McGinnis, Garber, Wirz, Kuroiwa and Gehring, 1984.) In the mouse, apart from the Hox clusters, there are at least five other homeobox genes, corresponding to specific Drosophila genes; others containing not only a homeobox sequence but a second motif, the paired box (Pax) and still other homeobox genes contain a POU-specific domain (Kessel and Gruss, 1990.)
Certain of the Pax genes, which are also found in Drosophila and the squid Loligo, are involved in the development of the eyes of all these species. It is possible that eyes found in all animals may be partly homologous! (Quiring et al, 1994; Gould, 1994.)
Changes in the Hox complex may be responsible for a variety of phenomena including: (1) the slight variations in rib numbers in fossil horses used as an argument against evolution by some creationists, (2) the shift in limb bud position in various vertebrates mentioned by de Beer, and (3) the partial homology of front and hind limbs. In the mouse, a Hox A11 mutant produces an enlarged sesamoid bone in both the fore and hind limbs (Small and Potter, 1993.) Is this the genetic basis for the panda's thumb?
The discovery of these all-pervading developmental genetic homologies underlying the diverse body plans of the animal phyla was an entirely unexpected phenomenon. Differences in body plans are partly due to differences in homeobox gene expression patterns and to the differences in the target genes regulated by them. The references cited below are only a fraction of the enormous literature on homeotic genes that has grown since 1984. See Gould (1991, 1994) and Ruddihough (1992b) for popular summaries of the homeobox genes.
Akam, M. 1989. Hox and HOM: Homologous Gene Clusters in Insects and Vertebrates. Cell 57(3): 347-349 (May 5.)
Akam, M. 1991. Wonderous transformation. Nature 349: 282 (24 January.)
Arendt, D. and K. Nubler-Jung. 1994. Inversion of dorsoventral axis? Nature 371: 26 (1 September.)
Awgulewitsch, A. and D. Jacobs. 1992. Deformed autoregulatory element from Drosophila functions in a conserved manner in transgenic mice. Nature 358: 341-344 (23 July.)
Balling, R., G. Mutter, P. Gruss and M. Kessel. 1989. Craniofacial Abnormalities Induced by Ectopic Expression of the Homeobox Gene Hox-1.1 in Transgenic Mice. Cell 58(2): 337-347 (July 28.)
Bateson, W. 1894. Materials for the study of variation treated with especial regard to discontinuity in the origin of species. Macmillan and Co., London and New York.
Beeman, R. W. 1987. A homeotic gene cluster in the red flour beetle. Nature 327: 247-249 (21 May).
Beeman, R. W., J. J. Stuart, S. J. Brown and R. E. Denell. 1993. Structure and Function of the Homeotic Gene Complex (HOM-C) in the Beetle, Tribolium castaneum. BioEssays 15(7): 439-444.
Boncinelli, E., A. Simeone, D. Acampora and F. Mavilio. 1991. HOX gene activation by retinoic acid. Trends in Genetics 7(10): 329-334 (October.)
Burglin, T. R., M. Finney, A. Coulson and G. Ruvkun. 1989. Caenorhabditis elegans has scores of homeobox-containing genes. Nature 341: 239-243 (21 September.)
Carpenter, E. M., J. M. Goddard, O. Chisaka, N. R. Manley and M. R. Capecchi. 1993. Loss of Hox-A1 (Hox-1.6) function results in the reorganization of the murine hindbrain. Development 118(4): 1603-1075 (August.)
Carrasco, A. E., W. McGinnis, W. J. Gehring and E. M. De Robertis. 1984. Cloning of an X. laevis Gene Expressed during Early Embryogenesis Coding for a Peptide Region Homologous to Drosophila Homeotic Genes. Cell 37(2): 409-414 (June.)
Chisaka, O. and M. R. Capecchi. 1991. Regionally restricted developmental defects resulting from targeted disruption of the mouse homeobox gene hox-1.5. Nature 350: 473-479 (11 April.)
Chisaka, O., T. S. Musci and M. R. Capecchi. 1992. Developmental defects of the ear, cranial nerves and hindbrain resulting from targeted disruption of the mouse homeobox gene Hox-1.6. Nature 335: 516-520 (6 February.)
Chuong, C-M. 1993. The Making of a Feather: Homeoproteins, Retinoids and Adhesion Molecules. BioEssays 15(8): 513-521.
Condie, B. G. and M. R. Capecchi. 1993. Mice homozygous for a targeted disruption of Hoxd-3 (Hox-4.1) exhibit anterior transformation of the first and second cervical vertebrae, the atlas and the axis. Development 119(3): 579-595 (November.).
Condie, B. G. and M. R. Capecchi. 1994. Mice with targeted disruptions in the paralogous genes hoxa-3 and hoxd-3 reveal synergistic interactions. Nature 370: 304-307 (28 July.)
Cowing, D. W. and C. Kenyon. 1992. Expression of the homeotic gene mab-5 during Caenorhabditis elegans embryogenesis. Development 116(2): 481-490 (October.)
Dolle, P., A. Dierich, M. LeMeur, T. Schimmang, B. Schuhbaur, P. Chambon and D. Duboule. 1993. Disruption of the Hoxd-13 Gene Induces Localized Heterochrony Leading to Mice with Neotenic Limbs. Cell 75(3): 431-441 (November 5.)
Dolle, P., J-C. Izpisua-Belmonte, H. Falkenstein, A. Renucci and D. Duboule. 1989. Coordinate expression of the murine Hox-5 complex homoeobox-containing genes during limb pattern formation. Nature 342: 767-772 (14 December.)
Dolle, P., T. Lufkin, R. Krumlauf, M. Mark, D. Duboule and P. Chambon. 1993. Local alterations of Krox-20 and Hox gene expression in the hindbrain suggest lack of rhombomeres 4 and 5 in homozygote null Hoxa-1 (Hox-1.6) mutant embryos. Proceedings of the National Academy of Sciences 90(16): 7666-7670 (August.)
Duboule, D. 1992. The Vertebrate Limb: A Model System to Study the Hox/HOM Gene Network during Development and Evolution. BioEssays 14(6): 375-384 (June.)
Garcia-Fernandez, J. and P. W. H. Holland. 1994. Archetypal organization of the amphioxus Hox gene cluster. Nature 370: 563-566. (18 August.) See also: Gee, H. 1994. Return of the amphioxus. Nature 370: 504-505 (18 August.)
Gaunt, S. J. 1991. Expression Patterns of Mouse Hox Genes: Clues to an Understanding of Developmental and Evolutionary Strategies. BioEssays 13(10): 505-513.
Gehring, W. J. 1985. Homeotic Genes, the Homeo Box, and the Genetic Control of Development. Cold Spring Harbor Symposia on Quantitative Biology 50: 243-251.
Gendron-Maquire, M., M. Mallo, M. Zhang and T. Gridley. 1993. Hoxa-2 Mutant Mice Exhibit Homeotic Transformation of Skeletal Elements Derived from Cranial Neural Crest. Cell 75(7): 1317-1331 (December 31.)
Gould, S. J. 1991. Of Mice and Mosquitoes. Natural History 100(7): 12-20 (July.).
Gould, S. J. 1994. Common Pathways of Illumination. Natural History 103(12): 10-20 (December.)
Graham, A., N. Papalopulu and R. Krumlauf. 1989. The Murine and Drosophila Homeobox Gene Complexes have Common Features of Organization and Expression. Cell 57(3): 367-378 (May 5.)
Hoey, T., H. J. Doyle, K. Harding, C. Wedeen and M. Levine. 1986. Homeo box gene expression in anterior and posterior regions of the Drosophila embryo. Proceedings of the National Academy of Sciences 83(13): 4809-4813 (July.)
Holland, P. 1992. Homeobox Genes in Vertebrate Evolution. BioEssays 14(4): 267-273.
Holland, P. W. H. and B. L. M. Hogan. 1986. Phylogenetic distribution of Antennapedia-like homoeo boxes. Nature 321: 251-253 (15 May.0
Holland, P. W. H., L. Z. Holland, N. A. WIlliams and N. D. Holland. 1992. An amphioxus homeobox gene: sequence conservation, spatial expression during development and insights into vertebrate evolution. Development 116(3): 653-661 (November.)
Hunt, P., M. Gulisano, M. Cook, M-H. Sham, A. Faiella, D. Wilkinson, E. Boncinelli and R. Krumlauf. 1991. A distinct Hox code for the branchial region of the vertebrate head. Nature 353: 861-864 (31 October.)
Izpisua-Belmonte, J-C., C. Tickle, P. Dolle, L. Wolpert and D. Duboule. 1991. Expression of the homeobox Hox-4 genes and the specification of position in chick wing development. Nature 350: 585-589 (18 April.)
Jeannotte, L., M. Lemieux, J. Charron, F. Poirier and E. J. Robertson. 1993. Specification of axial identity in the mouse: role of the Hoxa-5 (Hox1.3) gene. Genes and Development 7(11): 2085-2096.
Jegalian, B. G. and E. M. De Robertis. 1992. Homeotic Transformations in the Mouse Induced by Overexpression of a Human Hox3.3 Transgene. Cell 71(6): 901-910 (December 11.)
Kappen, C., K. Schughart and F. H. Ruddle. 1989. Two steps in the evolution of Antennapedia-class vertebrate homeobox genes. Proceedings of the National Academy of Sciences 86(14): 5459-5463 (July.)
Kaufman, T. C., R. Lewis and B. Wakimoto. 1980. Cytogenetic analysis of chromosome 3 in Drosophila melanogaster: the homoeotic gene complex in polytene chromosome interval 84A-B. Genetics 94: 115-133.
Kenyon, C. and B. Wang. 1991. A Cluster of Antennapedia-Class Homeobox Genes in a Nonsegmented Animal. Science 253: 516-517 (2 August.)
Kessel, M., R. Balling and P. Gruss. 1990. Variations of Cervical Vertebrae after Expression of a Hox-1.1 Transgene in Mice. Cell 61(2): 301-308 (April 20.)
Kessel, M. and P. Gruss. 1990. Murine Developmental Control Genes. Science 249: 374-379 (27 July.)
Kessel, M. and P. Gruss. 1991. Homeotic Transformations of Murine Vertebrae and Comcomitant Alteration of Hox Codes Induced by Retinoic Acid. Cell 67(1): 89-104 (October.)
Krumlauf, R. 1992. Evolution of the Vertebrate Hox Homeobox Genes. BioEssays 14(4): 245-252 (April.)
Le Mouellic, H., Y. Lallemand and P. Brulet. 1992. Homeosis in the Mouse Induced by a Null Mutation in the Hox-3.1 Gene. Cell 69(2): 251-254 (April 17.)
Levine, M., G. M. Rubin and R. Tjian. 1984. Human DNA Sequences Homologous to a Protein Coding Region Conserved between Homeotic Genes of Drosophila. Cell 38(3): 667-673 (October.)
Lewis, E. B. 1963. Genes and developmental pathways. American Zoologist 3: 33-56.
Lewis, E. B. 1978. A gene complex controlling segmentation in Drosophila. Nature 276: 565-570 (7 December.)
Lufkin, T., A. Dierich, M. LeMeur, M. Mark and P. Chambon. 1991. Disruption of the Hox-1.6 Homeobox Gene Results in Defects in a Region Corresponding to Its Rostral Domain of Expression. Cell 66(6): 1105-1119 (September 20.)
McGinnis, W. 1985. Homeo Box Sequences of the Antennapedia Class Are Conserved Only in Higher Animal Genomes. Cold Spring Harbor Symposia on Quantitative Biology 50: 263-270.
McGinnis, W., R. L. Garber, J. Wirz, A. Kuroiwa and W. J. Gehring. 1984. A Homologous Protein-Coding Sequence in Drosophila Homeotic Genes and Its Conservation in Other Metazoans. Cell 37(2): 403-408 (June.)
McGinnis, W., C. P. Hart, W. J. Gehring and F. H. Ruddle. 1984. Molecular Cloning and Chromosome Mapping of a Mouse DNA Sequence Homologous to Homeotic Genes of Drosophila. Call 38(3): 675-680 (October.)
McGinnis, N., M. A. Kuziora and W. McGinnis. 1990. Human Hox-4.2 and Drosophila Deformed Encode Similar Regulatory Specificities in Drosophila Embryos and Larvae. Cell 63(5): 969-976 (November 30.)
McGinnis, W., M. S. Levine, E. Hafen, A. Kuroiwa and W. J. Gehring. 1984. A conserved DNA sequence in homoeotic genes of the Drosophila Antennapedia and bithorax complexes. Nature 308: 428-433 (29 March.)
Maddox, J. 1984. Patterns of developing embryos. Nature 310: 9 (5 July.)
Malicki, J., L. C. Cianetti, C. Peschle and W. McGinnis 1992. A human HOX4B regulatory element provides head-specific expression in Drosophila embryos. Nature 358: 345-347 (23 July.)
Malicki, J., K. Schughart and W. McGinnis. 1990. Mouse Hox-2.2 Specifies Thoracic Segmental Identity in Drosophila Embryos and Larvae. Cell 63(5): 961-967 (November 30.)
Mark, M., T. Lufkin, J-L. Vonesch, E. Ruberte, J-C. Olivo, P. Dolle, P. Gorry, A. Lumsden and P. Chambon. 1993. Two rhombomeres are altered in Hoxa-1 mutant mice. Development 119(2): 319-338 (October.)
Marshall, H., M. Studer, H. Popperl, S. Aparicio, A. Kuroiwa, S. Brenner and R. Krumlauf. 1994. A conserved retinoic acid response element required for early expression of the homeobox gene Hoxb-1. Nature 370: 567-571 (18 August.)
Morgan, B. A., J-C. Izpisua-Belmonte, D. Duboule and C. J. Tabin. 1992. Targeted misexpression of Hox-4.6 in the avian limb bud causes apparent homeotic transformations. Nature 358: 236-239 (16 July.)
Murtha, M. T., J. F. Leckman and F. H. Ruddle. 1991. Detection of homeobox genes in development and evolution. Proceedings of the National Academy of Sciences 88(23): 10711-10715 (December.)
Pendleton, J. W., B. K. Nagai, M. T. Murtha and F. H. Ruddle. 1993. Expansion of the Hox gene family and the evolution of chordates. Proceedings of the National Academy of Sciences 90(13): 6300-6304 (July.)
Quiring, R., U. Walldorf, U. Kloter and W. J. Gehring. 1994. Homology of the eyeless Gene of Drosophila to the Small eye Gene in Mice and Aniridia in Humans. Science 265: 785-789 (5 August.) See also: Zuker, C. S. 1994. On the Evolution of Eyes: Would You Like It Simple or Compound? Science 265: 742-743 (5 August.)
Raff, R. A. and T. C. Kaufman. 1983. Embryos, Genes, and Evolution: The Developmental-Genetic Basis of Evolutionary Change. Macmillan Publishing Co. New York.
Ramirez-Solis, R., H. Zheng, J. Whiting, R. Krumlauf and A. Bradley. 1993. Hoxb-4 (Hox-2.6) Mutant Mice Show Homeotic Transformation of a Cervical Vertebra and Defects in the Closure of the Sternal Rudiments. Cell 73(2): 279-294 (April 23.)
Rennie, J. 1991. Homeobox Harvest. Scientific American 264(6): 24 (June.)
Riddihough, G. 1992a. Homing in on the homeobox. Nature 357: 643-644 (25 June.)
Riddihough, G. 1992b. A tale of two heads. New Scientist 135(1839): 38-42 (19 September.)
Rijli, F. M., M. Mark, S. Lakkaraju, A. Dierich, P. Dolle and P. Chambon. 1993. A Homeotic Transformation Is Generated in the Rostral Branchial Region of the Head by Disruption of Hoxa-2, Which Acts a Selector Gene. Cell 75(7): 1333-1349 (December 31.)
Schubert, F. R., K. Nieselt-Struwe, and P. Gruss. 1993. The Antennapedia-type homeobox genes have evolved from three precursors separated early in metazoan evolution. Proceedings of the National Academy of Sciences 90(1): 143-147 (January.)
Scott, M. F. 1992. Vertebrate Homeobox Gene Nomenclature. Cell 71(4): 551-553 (November 13.)
Shepherd, J. C. W., W. McGinnis, A. E. Carrasco, E. M. De Robertis and W. J. Gehring. 1984. Fly and frog homoeo domains show homologies with yeast mating type regulatory proteins. Nature 310: 70-71 (5 July.)
Simeone, A., D. Acampora, M. Gulisano, A. Stornaiuolo and E. Boncinelli. 1992. Nested expression domains of four homeobox genes in developing rostral brain. Nature 358: 687-690 (20 August.)
Slack, J. 1984. A Rosetta stone for pattern formation in animals? Nature 310: 364-365 (2 August.)
Slack, J. M. W., P. W. H. Holland and C. F. Graham. 1993. The zootype and the phylotypic stage. Nature 361: 490-492 (11 February.) See also Miller, D. J. and A. Miles. 1993. Homeobox genes and the zootype. Nature 365: 215-216 (16 September.)
Small, K. M. and S. S. Potter. 1993. Homeotic transformations and limb defects in Hox A11 mutant mice. Genes and Development 7(12a): 2318-2328 (December.)
Struhl, G. 1984. A universal genetic key to body plan? Nature 310:10-11 (5 July.)
Stuart, J. J., S. J. Brown, R. W. Beeman and R. E. Denell. 1991. A deficiency of the homeotic complex of the beetle Tribolium. Nature 350: 72-74 (7 March).
Tabin, C. J. 1992. Why we have (only) five fingers per hand: Hox genes and the evolution of paired limbs. Development 116(2): 289-296 (October.)
Tabin, C. and E. Laufer. 1993. Hox genes and serial homology. Nature 361: 692-693 (25 February.) See also: Coates, M., P. Thorogood, P. Ferretti, M. Kessel. 1993. Hox genes, fin folds and symmetry. Nature 364: 195-197 (15 July.)
Williams, J. A. and S. B. Carroll. 1993. The Origin, Patterning and Evolution of Insect Appendages. BioEssays 15(9): 567-577.
Wolgemuth, D. J., R. R. Behringer, M. P. Mosteller, R. L. Brinster and R. D. Palmiter. 1989. Transgenic mice overexpressing the mouse homoeobox-containing gene Hox-1.4 exhibit abnormal gut development. Nature 337: 464-467 (2 February.)
Wysocka-Diller, J. W., G. O. Aisemberg, M. Baumgarten, M. Levine and E. R. Macagno. 1989. Characterization of a homologue of bithorax-complex genes in the leech Hirudo medicinalis Nature 341: 760-763 (26 October.)
(from Frank Sonleitner's critique of Of Pandas and People)