State legislatures are considering, and some have passed, bills that would require the introduction of biblical creationism in science classes. Local school boards have passed ordinances to restrict the teaching of evolution or to require what is called a "balanced treatment" of creationism and evolution. Publishers of science textbooks are under pressure to deemphasize evolution while adding course material on "creation science."
The teaching of creationism as advocated by the leading proponents of "creation science" includes the following judgments: (1) the earth and universe are relatively young, perhaps only 6,000 to 10,000 years old; (2) the present form of the earth can be explained by "catastrophism," including a worldwide flood; and (3) all living things (including humans) were created miraculously, essentially in the forms we now find them. These teachings may be recognized as having been derived from the accounts of origins in the first two chapters of Genesis.
Generations of able and often devout scientists before us have sought evidence for these teachings without success. Others have given us hypotheses about the origin and history of the earth and the universe itself. These hypotheses have been tested and validated by many different lines of inquiry. With modifications to include new findings, they have become the central organizing theories that make the universe as a whole intelligible, lend coherence to all of science, and provide fruitful direction to modern research. The hypothesis of special creation has, over nearly two centuries, been repeatedly and sympathetically considered and rejected on evidential grounds by qualified observers and experimentalists. In the forms given in the first two chapters of Genesis, it is now an invalidated hypothesis. To reintroduce it into the public schools at this time as an element of science teaching would be akin to requiring the teaching of Ptolemaic astronomy or pre-Columbian geography.
Confronted by this challenge to the integrity and effectiveness of our national educational system and to the hardwon evidencebased foundations of science, the National Academy of Sciences cannot remain silent. To do so would be a dereliction of our responsibility to academic and intellectual freedom and to the fundamental principles of scientific thought. As a historic representative of the scientific profession and designated advisor to the Federal Government in matters of science, the Academy states unequivocally that the tenets of "creation science" are not supported by scientific evidence, that creationism has no place in a science curriculum at any level, that its proposed teaching would be impossible in any constructive sense for wellinformed and conscientious science teachers, and that its teaching would be contrary to the nation's need for a scientifically literate citizenry and for a large, well-informed pool of scientific and technical personnel.
The Central Scientific Issues
Five central scientific issues are critical to consideration of the treatment in school curricula of the origin and evolution of the universe and of life on earth . . . .
The Nature Of Science
It is important to clarify the nature of science and to explain why creationism cannot be regarded as a scientific pursuit. The claim that equity demands balanced treatment of the two in the same classroom reflects misunderstanding of what science is and how it is conducted. Scientific investigators seek to understand natural phenomena by direct observation and experimentation. Scientific interpretations of facts are always provisional and must be testable. Statements made by any authority, revelation, or appeal to the supernatural are not germane to this process in the absence of supporting evidence. In creationism, however, both authority and revelation take precedence over evidence. The conclusions of creationism do not change, nor can they be validated when subjected to test by the methods of science. Thus, there are profound differences between the religious belief in special creation and the scientific explanations embodied in evolutionary theory. Neither benefits from the confusion that results when the two are presented as equivalent approaches in the same classroom. . . .
Special creation is neither a successful theory nor a testable hypothesis for the origin of the universe, the earth, or of life thereon. Creationism reverses the scientific process. It accepts as authoritative a conclusion seen as unalterable and then seeks to support that conclusion by whatever means possible.
In contrast, science accommodates, indeed welcomes, new discoveries: its theories change and its activities broaden as new facts come to light or new potentials are recognized. Examples of events changing scientific thought are legion. Prior acceptance of the fixed ad hoc hypothesis of creationism — ideas that are certified as untestable by their most ardent advocates — would have blocked important advances that have led to the great scientific achievements of recent years. Truly scientific understanding cannot be attained or even pursued effectively when explanations not derived from or tested by the scientific method are accepted.
Scientific Evidence On The Origin Of The Universe And The Earth
The processes by which new galaxies, stars, and our own planetary system are formed are sometimes referred to as the "evolution" of the universe, the stars, and the solar system. The word evolution in this context has a very different meaning than it does when applied to the evolution of organisms.
Evidence that the evolution of the universe has taken place over at least several billion years is overwhelming. Among the most striking indications of this process are the receding velocities of distant galaxies. This general expansion of the universe was first noted in the late 1920s and early 1930s. Astronomers today estimate that the expansion probably began some 10 to 20 billion years ago.
The invariant spontaneous decay of the radioactive isotopes of some elements provides further evidence that the universe is billions of years old. Analyses of the relative abundances of radioactive isotopes and their inert decay products in the earth, meteorites, and moon rocks all lead to the conclusion that these bodies are about 4.5 billion years old.
A major assertion for the creationists' opposition to the geological record and evolution is their belief that earth is relatively young, perhaps only a few thousand years old. In rejecting evidence for the great age of the universe, creationists are in conflict with data from astronomy, astrophysics, nuclear physics, geology, geochemistry, and geophysics. The creationists' conclusion that the earth is only a few thousand years old was originally reached from the timing of events in the Old Testament. . . .
The Scientific Standing Of Biological Evolution
Although it was Darwin, above all others, who first marshaled the convincing critical evidence for biological evolution, earlier alert scholars recognized that the succession of living forms on the earth had changed systematically within the passage of geological time.
As applied to biology, a distinction is to be drawn between the questions (1) whether and (2) how biological evolution happened. The first refers to the finding, now supported by an overwhelming body of evidence, that descent with modification occurred during more than 2.7 billion years of earth's history. The second refers to the theory explaining how those changes developed along the observed lineages. The mechanisms are still undergoing investigation; the currently favored theory is an extensively modified version of Darwinian natural selection.
With that proviso we will now consider three aspects of biological evolution in more detail. . . .
Relation by Common Descent: Evidence for relation by common descent has been provided by paleontology, comparative anatomy, biogeography, embryology, biochemistry, molecular genetics, and other biological disciplines. The idea first emerged from observations of systematic changes in the succession of fossil remains found in a sequence of layered rocks. . . .
In Darwin's time, however, paleontology was still a rudimentary science, and large parts of the geological succession of stratified rocks were unknown or inadequately studied. Darwin, therefore, worried about the rarity of truly intermediate forms. Creationists have then and now seized on this as a weakness in evolutionary theory. Indeed, although gaps in the paleontological record remain even now, many have been filled with the researches of paleontologists since Darwin's time. Hundreds of thousands of fossil organisms found in welldated rock sequences represent a succession of forms through time and manifest many evolutionary transitions. . . There have been so many discoveries of intermediate forms between fish and amphibians, between amphibians and reptiles, between reptiles and mammals, and even along the primate line of descent that it is often difficult to identify categorically the line to which a particular genus or species belongs.
Although creationists claim that the entire geological record, with its orderly succession of fossils, is the product of a single universal flood that lasted a little longer than a year and covered the highest mountains to a depth of some 7 meters a few thousand years ago, there is clear evidence in the form of intertidal and terrestrial deposits that at no recorded time in the past has the entire planet been under water. The belief that all this sediment with its fossils was deposited in an orderly sequence in a year's time defies all geological observations and physical principles concerning sedimentation rates and possible quantities of suspended solid matter. We do not doubt that there were periods of unusually high rainfall or that extensive flooding of inhabited areas has occurred, but there is no scientific support for the hypothesis of a universal, mountaintopping flood.
Inferences about common descent derived from paleontology have been reinforced by comparative anatomy. The skeletons of humans, dogs, whales, and bats are strikingly similar, despite the different ways of life led by these animals and the diversity of environments in which they have flourished. The correspondence, bone by bone, can be observed in every part of the body, including the limbs. Yet a person writes, a dog runs, a whale swims, and a bat flies — with structures built of the same bones. Scientists call such structures homologous and have concurred that they are best explained by common descent.
Biogeography also has contributed evidence for common descent. . . . Creationists contend that the curious facts of biogeography result from the occurrence of a special creationary event. A scientific hypothesis proposes that biological diversity results from an evolutionary process whereby the descendants of local or migrant predecessors became adapted to their diverse environments. A testable corollary of that hypothesis is that present forms and local fossils should show homologous attributes indicating how one is derived from the other. Also, there should be evidence that forms without an established local ancestry had migrated into the locality. Whenever such tests have been carried out, these conditions have been confirmed.
Embryology, the study of biological development from the time of conception, is another source of independent evidence for common descent. Barnacles, for instance, are sedentary crustaceans with little apparent similarity to such other crustaceans as lobsters, shrimps, or copepods. Yet barnacles pass through a freeswimming larval stage, in which they look unmistakably like other crustacean larvae. The similarity of larval stages supports the conclusion that all crustaceans have homologous parts and a common ancestry.
Molecular Biology and the Degree of Relationship: Very recent studies in molecular biology have independently confirmed the judgments of paleontologists and classical biologists about relationships among lineages and the order in which species appeared within lineages. They have also provided detailed information about the mechanisms of biological evolution.
DNA, the hereditary material within all cells, and the proteins encoded by the genes in the DNA both offer extensive information about the ancestry of organisms. Analysis of such information has made it possible to reconstruct evolutionary events that were previously unknown, and to confirm and date events already surmised but not precisely dated.
In unveiling the universality of the chemical basis of heredity, molecular biology has profoundly affirmed common ancestry. In all organisms — bacteria, plants, and animals, including humans — the hereditary information is encoded in DNA, which is in all instances made up of the same four subunits called nucleotides. The genetic code by which the information contained in the nuclear DNA is used to form proteins is essentially the same in all organisms. Proteins in all organisms are invariably composed of the same 20 amino acids, all having a "lefthanded" configuration, although there are amino acids in nature with both "right" and "lefthanded" configurations. The metabolic pathways through which the most diversified organisms produce energy and manufacture cell components are also essentially the same. This unity reveals the genetic continuity of living organisms, thereby giving independent confirmation of descent from a common ancestry. There is no other way consistent with the laws of nature and probability to account for such uniformity. . . .
Studies in evolutionary biology have led to the conclusion that mankind arose from ancestral primates. This association was hotly debated among scientists in Darwin's day, before molecular biology and the discovery of the now abundant connecting links. Today, however, there is no significant scientific doubt about the close evolutionary relationships among all primates or between apes and humans. The "missing links" that troubled Darwin and his followers are no longer missing. Today, not one but many such connecting links, intermediate between various branches of the primate family tree, have been found as fossils. These linking fossils are intermediate in form and occur in geological deposits of intermediate age. They thus document the time and rate at which primate and human evolution occurred.
The Origin Of Life
Scientific research on the origin of life is in an exploratory phase, and all its conclusions are tentative. We know that the organisms that lived on earth 2 billion or more years ago were simply microbial forms. . . . Experiments conducted under plausible primitiveearth conditions have resulted in the production of amino acids, large protein-like molecules made from long chains of amino acids, the nucleotide components of DNA, and DNA-like chains of these nucleotides. Many biologically interesting molecules have also been detected by astronomers using radiotelescopes. We can, therefore, explain how the early oxygen-free earth provided a hospitable site for the accumulation of molecules suitable for the construction of living systems.
For those who are studying aspects of the origin of life, the question no longer seems to be whether life could have originated by chemical processes involving nonbiological components but, rather,what pathway might have been followed. The data accumulated thus far imply selective processes. Prebiological chemical evolution is seen as a trial-and-error process leading to the success of one or more systems built from the many possible chemical components. The system that evolved with the capability of self-replication and mutation led to what we now define as a living system.
Scientists, like many others, are touched with awe at the order and complexity of nature. Religion provides one way for human beings to be comfortable with these marvels. However, the goal of science is to seek naturalistic explanations for phenomena — and the origins of life, the earth, and the universe are, to scientists, such phenomena — within the framework of natural laws and principles and the operational rule of testability.
It is, therefore, our unequivocal conclusion that creationism, with its account of the origin of life by supernatural means, is not science. It subordinates evidence to statements based on authority and revelation. Its documentation is almost entirely limited to the special publications of its advocates. And its central hypothesis is not subject to change in light of new data or demonstration of error. Moreover, when the evidence for creationism has been subjected to the tests of the scientific method, it has been found invalid.
No body of beliefs that has its origin in doctrinal material rather than scientific observation should be admissible as science in any science course. Incorporating the teaching of such doctrines into a science curriculum stifles the development of critical thinking patterns in the developing mind and seriously compromises the best interests of public education. This could eventually hamper the advancement of science and technology as students take their places as leaders of future generations.