You are here
Problem Concepts in Evolution
Problem Concepts in Evolution: Cause, Purpose, Design, and Chance
by Eugenie C. Scott
ABSTRACTThe American student population is largely religious and a significant minority rejects evolution. Evolution and other scientific theories are restricted to explaining through natural cause (methodological materialism), but because evolution has existential connotations, many students confuse the ability to explain through natural cause with a conclusion that therefore God does not exist (philosophical materialism). To some, if God does not exist, life has no purpose or meaning, and acceptance of evolution brings on an existential crisis. Differing understandings of four concepts (cause, purpose, design, and chance) commonly used in the teaching of evolution may exacerbate antievolutionism if students conflate their own existential meanings of these terms with the definitions within science. Cause, purpose, and design to many students include the notion of supernatural cause, purpose, and design, whereas chance is often thought to mean "purposeless" or "random" (in the sense of unpredictable.) Professors should teach evolution in a religiously-neutral fashion, thus allowing religious students to accommodate their religious views to science.
ATTITUDES TOWARDS EVOLUTIONSince 1982 the Gallup organization has asked American adults three questions about creation and evolution. "God created mankind pretty much in his present form over the last 10,000 years." "Mankind has developed over millions of years from less advanced forms of life, but God guided this process, including mankind’s creation." "Mankind has developed over millions of years from less advanced forms of life. God had no part in the process." Gallup’s surveys of attitudes towards creation and evolution have provided very consistent answers over time, as shown in Table 1. A large percentage of Americans accept young earth creationism, but an equal number accept theistic evolution. If all evolutionists are counted together, one can conclude that a majority of Americans accept evolution, but the high percentage of individuals who answer "agree" to the first question is nonetheless disturbing.
Most researchers explain American’s rejection of evolution as being at least partly due to the high degree of religious affiliation in the United States (Morin, 1998). College students resemble the general population in being primarily Christian, and having a low percentage of nonbelievers. A survey of students in California, Connecticut and Texas reported 76% identified themselves as Christian and 11% as non believers (calculated from Feder, 1995). A higher percentage of college students accept evolution than the general public.
Solid data on what college students think about evolution are not easy to come by. I am unaware of survey of a randomized sample of college students, weighted for the usual demographic variables, and controlled for numbers of years of science classes. I report here on two published national studies of attitudes or knowledge of students towards evolution, that for various reasons, are not comparable (or generalizable to all students) but which seem to be pointing in the same direction.
Almquist and Cronin requested college teachers attending their "Chautauqua" courses on human evolution to survey their students (Almquist and Cronin, 1988). The 2,100 questionnaires were collected between 1974 and 1983. The sample consisted of 47% females and 53% males, 84% of whom were under 25, and 73% of whom were freshmen or sophomores. Sixty percent had completed one or more courses in biological science, and a third had had one or more courses in anthropology. The sample was fairly well spread over five geographic areas of the US: East, South, Midwest, Southwest, and West.
Table 1: Gallup Poll on Creation and Evolution, 1982-1997(Bishop, 1998)
The authors found that although students exhibited some knowledge of evolution, they also lacked understanding of many fundamental concepts such as radiometric dating. They also found rather high acceptance of such creationist beliefs as humans and dinosaurs having coexisted, and the literal truth of the Bible. Differences existed among regions, with the lowest frequency of creationist beliefs occurring in the East (Table 2).
Table 2: Data from Almquist and Cronin 1988
During the mid-1980s, Feder, Eve and Harrold surveyed 979 college students from regionally-distributed universities: in the East, (Central Connecticut State University); the south, (University of Texas-Arlington and Texas Christian University); and in the West (the University of Southern California and Occidental College). Feder described the sample as including "a wide range of college students representing differing regions and social classes, races, and religions. They are predominantly young, white, politically moderate, and somewhat religious. They tend to read little, and many are in preprofessional programs. In all likelihood, our group is a fairly representative sample of college students in the United States" (Feder, 1995:43). Southern students were again the most conservative (Harrold and Eve, 1995). (Table 3)
According to these data, at least one in five college students has serious doubts about evolution. The statement, "There is plenty of scientific evidence against evolution in favor of the Bible’s account of creation" was agreed to by almost a quarter of the California students, nearly a third of the Connecticut students, and over 40% of the Texas students.
Both of these studies are over a decade old, and in fact, some of the data from the Almquist and Cronin study were collected in the 1970's, so conclusions may not be fully relevant to students today. A 1999 Gallup survey of American teenagers suggests, however, that the current crop of students may not be very friendly to evolution. Ninety-two percent consider religion to be "important" to them. When asked whether they would accept a scientific or a religious explanation when these explanations disagree with one another, 64% declared they are "more likely to accept the religious answer", and only 27% said they were more likely to accept a scientific answer. About 9% had no opinion, or would accept both explanations (Gallup and Gallup, 1999).
What is the significance of these studies for college teaching? Given that a substantial portion of a professor’s class might be resistant to accepting the idea of evolution, what can be done to encourage not just the learning of evolution, but its acceptance?
Table 3: Harrold and Eve, 1995
Elsewhere I have presented suggestions for "dealing with antievolutionism" (Scott, 1996). Here I look at how the manner in which professors or teachers present four concepts can make a significant difference to students’ acceptance of evolution. These concepts are cause, purpose, design, and chance.
To members of the non-scientific public, these terms have existential meanings beyond their meanings within science. Students may assume that by ignoring these, a professor is making an antireligious statement. In truth, silence on these existential subjects reflects the fact that science is neutral to religion.
Anthropologists define religion as a set of beliefs and rules associated with a nonmaterial (or supernatural) world (rather than a "world view" or "personal philosophy). Science, however, is an attempt to explain the natural world using natural, not supernatural causes. This methodological materialism distinguishes science from religion, which is allowed by its internal rules to recognize supernatural causation. Science requires testing of alternate explanations. If to test something requires the ability to hold constant certain effects, this means that omnipotent powers cannot be used as part of scientific explanations. Logically, if there are omnipotent powers in the universe, it is impossible to hold their effects constant, to "control" them in the scientific sense. An omnipotent power could interfere, not interfere, or interfere but make it look like it isn’t interfering. It is therefore inappropriate in a science class to either promote or denigrate religious (supernatural) explanations for natural processes.
Individual scientists can and do hold strong beliefs about the existence or nonexistence of God, but when teaching science, one should be religiously-neutral — for practical as well as philosophical reasons. If students believe that they must choose between science/evolution and religion, we will decrease the level of science literacy even below its present dismal level. Of course, the view that one must choose one or the other, which is promoted by antievolutionists is a false one: theologically, Catholicism and most Protestant denominations accept theistic evolution (Matsumura, 1998). Given a chance, most religious students can accommodate their religious views to science, i.e., accommodation is possible if evolution is not taught as materialist philosophy.
Let us look, then, at scientific and public meanings of these problem concepts, and some suggestions for avoiding possible miscommunications.
CauseScientific Meaning of Cause Modern biologists recognize two classes of causes: proximate (or immediate) and ultimate or indirect causes (Mayr, 1991; Williams, 1992). Goldsmith describes proximate cause as "what one can see" and ultimate causes as invoking "the concept of adaptation of organs to their environment as well as evolutionary inferences..." (Goldsmith, 1991:6). The proximate cause of sexual dimorphism in a bird’s plumage is hormonal differences between males and females, but the ultimate cause is natural selection (Mayr, 1991).
Public Meaning of Cause As do scientists, members of the nonscientific public recognize more than one level of "cause". The proximate cause of the slayings of teenagers at Columbine High School in Colorado was two boys who opened fire on their schoolmates, and there has been wide speculation about the secondary causes: the availability of guns, the individual life histories of the two boys, the pervasive violent entertainments enjoyed by young people, and so on. The public tends to answer most questions about the natural world through proximate cause. A well-known educational videotape ("A Separate Universe") begins with a hilarious if depressing series of interviews of still-mortarboarded Harvard graduating seniors who are asked, "What causes the seasons?" Even though most of them couldn’t answer the question correctly, the answers they attempted were material in nature. No one invoked God’s hand, or claimed that seasons occur because of the innate nature of the sun, or other mystical causes. Students attempted to answer the question scientifically — regardless of their failure to do so.
However, had the investigators asked the question, "Why is there something rather than nothing?" the answers would likely have included both scientific and nonscientific (supernatural) causes. Existential questions are treated differently from more mundane questions such as "What is the cause of metamorphosis", and understanding how people think about and answer such questions is central to understanding the opposition to evolution (Pennock, 1996 C/E).
Divine cause is commonly invoked with respect to existential questions or questions with existential connotations. The nonscientific public does not feel the need to use God’s intervention as an explanation for El Nino, or the ups and downs of the stock market, but rather easily adds divine intentions to the list of causes/explanations for such questions as "Does life have meaning? Is there purpose to existence? Why are there people?" And the question that is addressed by evolution, "How did everything get here?"
Because of the principle of methodological materialism, science does not employ divine causation as an explanation, and students need to have this point explicitly made. Professors should teach that there are three levels of causation: Proximate or immediate causes, which are in large part observable. Hunger in a lab rat is caused by the secretion of certain gastric juices that cause the stomach to contract, which causes a chain of impulses to be sent to the brain resulting in the rat seeking food. A pair of songbirds will rear more chicks from a clutch if a third, nonparent bird helps to feed them. Secondary or remote cause, which are inferred, rather than being directly observed. The lab rat’s gastric juices biochemically are very similar to the gastric juices of mice because rats and mice shared a recent common ancestor. Natural selection explains the "helper at the nest" phenomenon because the helper (a daughter from an earlier clutch) under certain conditions will leave more copies of her genes by helping her parents raise another brood than by trying to raise her own. Ultimate or divine/supernatural causes, which also are inferred, and which explain by evoking forces outside of what science can study. Point out to students that because this is a science class, and because science deals only with material (matter and energy) cause, only the first two explanations will be discussed and analyzed. The third cause is a matter of faith, not science. (Note that I am using "ultimate" differently than do Mayr and Williams. Because the nonscientific public is more likely to think of "ultimate" as a superlative -- as in "ultimate truths" -- I believe it is more likely to think of supernatural causation in conjunction with this term. Using Ultimate, with a capital letter, helps to illustrate this.)
Because evolution has implications for existential questions, students can easily overlook the fact that it also deals with questions that are strictly material. In a science class, the focus must be upon the strictly naturalistic proximate and secondary explanations of science. When the different levels of causation and their role in scientific thought is clearly stated, students can recognize that the neutrality of science towards religion doesn’t require individuals to be neutral. The goal here is to honestly present science and evolution, and to do so in a way that spares religious students -- the majority in most colleges -- from having to make a choice between science and religion.
Design and PurposeScientific Meaning of Design Scientists use design in two ways. Sometimes they speak informally of a structure having a design that allows an organism to do something. The shape of an orchid encourages pollination by a particular species of insect. In this descriptive sense, all that is meant by design is that parts work together to get something done. This was the sense in which the 19th century cleric William Paley used design. The purpose of a structure was "what it was good for", and the design was how it achieved its purpose. If the purpose of the vertebrate eye is to allow an organism to visually perceive its environment, the design of the eye (lens, ocular muscles, retina, rods, cones, etc) was how the eye achieved its purpose.
Design is also linked with teleology, as the means by which a goal is achieved, often with the connotation of supernatural causation. Paley argued that just as a complex artifact like a watch is proof of the existence of a watchmaker, so is the intricacy of the natural world proof of the existence of a divine designer. Because of methodological materialism, scientists cannot use the explanation of divine design, which is untestable and therefore outside of science. Final cause cannot be used in scientific explanations. Historically, Paley’s Argument from Design was abandoned after Darwin devised natural selection, a purely natural explanation for the fit between the structure of organism and the activities or functions they performed. Religious scientists of the late 19th century managed to view natural selection as a cause of design in living things much as they viewed gravitation as the cause of the planets staying in their orbits (Numbers, 1998). Direct supernatural cause gave way to indirect supernatural cause for these religious scientists. God’s agency was preserved, while science could proceed in a methodologically-materialistic fashion.
Public Meaning of Design But just as the public thinks of both material cause and Ultimate cause, it thinks of "design" in terms of a design er, much as did Paley. A natural, agent-less cause like natural selection is difficult for most Americans to understand. Religious students are likely to interpret a teacher’s saying "there is no design in nature" to mean "God had nothing to do with it", which is a statement outside of science. Professors should regularly emphasize to students that science is limited to natural explanations, thus whether there is an Ultimate design is a matter for individual student choice or rejection, not scientific test. This leaves the door open for students to make their own choices.
Purpose: Scientist’s Meaning In addition to using purpose to informally describe that which a structure achieves, scientists sometimes use it as a synonym of orthogenesis. Orthogenesis, a type of goal-directed evolution, is the idea that a lineage has a tendency to evolve in a particular way, and it may or may not be associated with teleology (Numbers, 1998). Orthogenesis is nicely represented in Emerson’s poem Mayday , where "...striving to be men the worm/Mounts through all the spires of form".
Orthogenesis is thoroughly rejected by paleontologists and other evolutionary biologists. The appearance of single-toed, hypsodont equids in the Pleistocene was not the inevitable result of horse evolution: Miocene multi-toed grazers and browsers were not "on their way" to becoming Equus , but were successful species in their own rights. So paleontologists accurately say that "evolution shows no purpose" meaning that evolution is not orthogenetic. But is this the same as what the nonscientific public understands by "purpose"?
Purpose: Public Meaning It is my experience that, to the nonscientific public, "purpose" connotes not only the ideas of orthogenesis and the uses of a structure, but also existential meaningfulness. The public looks at purpose both as "what is the vertebrate eye used for?" and "what is the purpose (meaning) of life?" Because most Americans believe in God, a sense of meaningfulness and thus purpose, is tied to religion, and one can anticipate a strong reaction when evolution is described as "purposeless."
When members of the nonscientific public hear a sentence such as "Man is the result of a purposeless and natural process that did not have him in mind." (Simpson, 1967:344) or "The important claim of "evolution" is that life developed gradually from nonliving matter to its present state of diverse complexity through purposeless natural mechanisms that are known to science". (Johnson, 1990:33) the former by a distinguished evolutionary biologist and the latter by a modern antievolutionist, they misled into thinking that evolution is inherently antireligious. Such misunderstandings are a major barrier to the public’s acceptance of evolution. But statements of Ultimate cause are outside of science. It is justified for a paleontologist to state that the evidence of the fossil record does not indicate that species evolved in linear fashion towards specific, internally-directed goals, but a lack of evidence for orthogenesis does not require the abandonment of belief in God or even of some role for God in producing the current diversity of life. Theology is flexible: a minister once told me that his theology required that intelligent life aware of a God should evolve; that it took the form of a pentadactyl featherless biped was immaterial. To him, God’s purpose could be realized regardless of the physical form of humankind; we could still be "made in the image of God" whether we had four fingers, scales, or cryptic coloration. To say that the contingencies of evolution disprove the theological idea that God created with a purpose is to misunderstand theology — and probably evolution as well.
Similarly, it is not scientific to claim that the evidence of the fossil record shows that evolution is purposeless. If there is an omnipotent being, it could have had one-toed grazers in mind all along, and have intended for horses of the Pleistocene to evolve to their present form. Science can neither demonstrate nor refute this, the intents and actions of supernatural omnipotent forces being outside of its ability to control and therefore test.
I suggest that professors and teachers distinguish scientific usages of design and purpose from the more existential meanings of these terms that students will have in mind. Much as with the teaching of causation, it should be made clear to students that the nature of science says nothing about Ultimate purpose, design, and direction of evolution. All science can tell us is that the fossil record and the nature of human variation suggest that many contingencies affect the history of lineages through time, and that there is no evidence of orthogenesis. Ultimately, whether there is existential purpose and meaning or direction to the universe is a matter of individual philosophy, not scientific proof.
Chance/RandomChance: Scientific Meanings In science, we commonly speak of the chance of something happening, meaning that it will occur according to a known probability. The chance (probability) of getting a homozygous recessive in a heterozygous cross is one in four. The chance of getting a head in a fair coin toss is 1/2. We also commonly use chance to refer to equal probabilities, as in changes which may occur due to fluctuations of genes or traits in a nonselective environment. If body size is not being selected for or against in a species, by "chance" the species size may increase through time (Ridley, 1993). Genetic drift, the nonadaptive fluctuations of genes due to sampling error, is often referred to as "changes occurring by chance ."
Random is used in this fashion: the technical meaning of random is that occurrences are governed by equal probability. In a table of two-digit random numbers, the numbers 59 and 24 have equal probability of being drawn. We modify this definition slightly when we discuss random mating, referring to genotypes having a probability of mating proportional to their frequency in the gene pool. If the frequency of gene b in a two allele system is .07, by Hardy-Weinberg, the probability that two gametes carrying b will unite to form homozygous genotype bb will be .0049. This is not usually the way the nonscientific public uses the terms chance and random, however.
Chance: Public Meanings In newspapers, on television and in other popular media, we can occasionally find "chance" and "random" being used in the probabilistic sense, but there is not much evidence that this sense is very well grasped by the public. Genetic counselors have a difficult time getting members of the nonscientific public to understand basic probabilities such as "one chance in four". Mathematical illiteracy in the American public is well-known to every teacher of freshmen college students.
More commonly, chance and random are used nonprobabilistically, and have very different, existential connotations. We read in newspapers of random violence, and the writers do not mean that everyone has an equal chance of being sampled, but that such violence is meaningless and purposeless. It is the most frightening form of violence because it is unpredictable — you just don’t know what will happen, or why. Ironically, scientists use the concepts of random and chance to make predictions, which is the direct opposite of their connotation in ordinary usage.
Antievolutionists regularly contrast design (created) with evolution ("chance"). They are harking back to Paley’s fundamental argument, that complex structures could not have occurred "by chance" — the Boeing 707 could not have assembled itself from airplane parts when a tornado blew through the hangar. Although creationists discuss the "improbability" of an amino acid sequence assembling "by chance", they use chance primarily to mean "things falling into place with no planning or purpose". Nonscientists, encouraged by antievolutionists, oppose "natural" to "designed", not realizing that a natural process (natural selection) can produce design. Because antievolutionists regularly equate natural selection with chance, professors should explicitly show why this is false.
Most students do not understand that evolution and natural selection are separate concepts, the former referring to the inference of common ancestry of living things and the latter to the major mechanism affecting this descent with modification. All evolutionary change involves differential reproduction; some individuals (or genotypes) leave more or fewer offspring than others. Some differential reproduction is due to chance (drift) and some to the positive or negative value of genetically-determined traits in a particular environment. Natural selection is adaptive differential reproduction, which is the antithesis of public view of chance. Chance (probability) is relevant to natural selection only in relation to the genetic variation on which natural selection operates. Even so, it must be made clear to students that this use of chance is the scientists’ probabilistic term, not the public’s "unpredictable, senseless" use of chance. Genetic variation produced by recombination and other Mendelian mechanisms has probabilistic (chance) elements, and is thus predictable -- the opposite of what the public thinks of "chance". Mutations are a result of "chance" in this probabilistic sense: mutations occur at a predictable rate, as in the mutation of B to b occurs one in every 100,000 gametes. We don’t know which particular gamete is going to carry a mutation, but within the population, there is some predictability regarding the overall frequency to be expected in the next generation. This is not "chance" in the public’s sense of the term. A subtle scientific point about mutation is that the cause of mutations is random with respect to the "need" of the organism or population for that trait.
So if we are to expect students to understand scientific use of terms like chance and random, we will have to be specific about how we use these terms, and be especially careful not to leave students with the impression that natural selection, is a "chance" process.
CONCLUSIONI have suggested that four terms, cause, purpose, design, and chance are used differently in science than they are in the general public, and because of existential meanings the nonscientific public attributes to these terms, their proper explication is especially pertinent to the teaching of evolution. Professors and teachers should keep in mind the potential for miscommunication, and make explicit the differences between the students’ "street" use of these terms and the way they are used in science class. Because students and the American nonscientific population in general are highly religious, and have a low acceptance of evolution, I have also recommended that teachers and professors not force students to make an unnecessary choice between evolution and faith. Professors should be clear that the methodological materialism of science does not require philosophical materialism. What should be avoided is presenting scientific ideas in a fashion that slams the door in the face of a religious student.
Evolution is an important topic in the biology and geology curriculum, and should be taught and taught accurately at the appropriate K-12 level. Many teachers do not teach evolution, and many teach it inaccurately. A teacher who does not feel knowledgeable about a subject is less likely to teach it. A teacher who does not accept evolution is unlikely to teach it, or will mislead students by teaching it as "incorrect science". In most states, future teachers receive their understanding of evolution and science as a way of knowing from science faculty, not from the schools of education. There are indications that professors of science are dropping the ball here: although data are scanty, it appears that both the knowledge and acceptance of evolution by teachers is wanting.
A number of state surveys of teachers have been conducted over the years, and although the questions, samples, dates of distribution and many other factors are not comparable, the data all seem to point in the same direction: a surprising number of practicing teachers do not accept evolution, and do not understand key concepts. In Table 4, I present data culled from a number of studies (states and dates indicated) in which teachers were asked about giving "equal time" to creationism in their science classes. Roughly one third look favored this possibility. I think such results reflect teachers’ profound misunderstanding of the nature of science. More attention needs to be spent (especially in the introductory courses, where future teachers receive their understanding of science) on both evolution and as science as a way of knowing.
Table 4: Percentage of Teachers Advocating Equal Time for Creationism Professors have a big job ahead of them.
REFERENCES CITEDAguillard, D. 1999. Evolution Education in Louisiana Public Schools: A Decade Following Edwards v Aguillard. American Biology Teacher 61: 182-188.
Almquist, A. and J. E. Cronin. 1988. Fact, Fancy and Myth on Human Evolution. Current Anthropology 29: 520-523.
Bishop, G. 1998. The Religious Worldview and American Beliefs About Human Origins. The Public Perspective 39-44.
Elgin, P. G. 1983. Creationism vs. Evolution: A Study of the Opinions of Georgia Teachers, Creationism vs. Evolution: A Study of the Opinions of Georgia Teachers. George State University, Atlanta, GA.
Eve, R. A. and D. Dunn. 1990. Psychic Powers, Astrology and Creationism in the Classroom? Evidence of Pseudoscientific Beliefs Among High School Biology and Life Science Teachers. American Biology Teacher 52: 10-21.
Feder, K. L. 1995. Cult Archaeology and Creationism: A Coordinated Research Project. In F. B. Harrold and R. A. Eve (eds), Cult Archaeology and Creationism: University of Iowa Press, Iowa City, pp. 34-48.
Gallup, G. and A. Gallup. 1999. Teen-agers Favor Religious Explanations Over Science, Baton Rouge Advocate, March 27, 1999, Baton Rouge, LA, pp. 2E.
Goldsmith, T. H. 1991. The Biological Roots of Human Nature; Forging Links Between Evolution and Behavior. Oxford University Press, New York.
Harrold, F. B. and R. A. Eve. 1995. Patterns of Creationist Belief Among College Students. In R. A. Eve and F. B. Harrold (eds), Cult archaeology and Creationism. University of Iowa Press, Iowa City, pp. 68-90.
Johnson, P. E. 1963. A Reply To My Critics. In P. E. Johnson (ed) Evolution as Dogma. Foundation for Thought and Ethics, Dallas, TX, pp. 33-37.
Matsumura, M. 1998. What Do Christians Really Believe About Evolution? Reports of the National Center for Science Education 18: 8-9.
Mayr, E. 1991. One Long Argument: Charles Darwin and the Genesis of Modern Evolutionary Thought. Harvard University Press, Cambridge, MA.
Morin, R. 1998. Keeping the Faith: A Survey Shows the United States Has the Most Churchgoing People In the Developed World, The Washington Post National Weekly Edition, January 12, 1998, Washington, DC, pp. 37.
Nickels, M. K. and B. A. Drummond. 1985. Creation/Evolution: Results of a Survey Conducted at the 1983 ISTA Convention. ISTA Spectrum 11: 11-15.
Numbers, R. L. 1998. Darwinism Comes to America. Harvard University Press, Cambridge, MA. Osif, B. A. 1997. Evolution & Religious Beliefs: A Survey of Pennsylvania High School Teachers. American Biology Teacher 59: 552-556.
Pennock, R. T. 1996. Naturalism, Creationism and the Meaning of Life: The Case of Phillip Johnson Revisited. Creation/Evolution 16 (39): 10-30.
Ridley, M. 1993. Evolution. Blackwell Scientific Publications, Oxford.
Scott, E. C. 1996. Dealing With Antievolutionism. In J. Scotchmoor and F. K. McKinney (eds), Learning Through the Fossil Record. Paleontological Society Papers. The Paleontological Society, Pittsburgh, PA, pp. 15-28.
Simpson, G. G. 1967. The Meaning of Evolution. Yale University Press, New Haven, CT.
Tatina, R. 1989. South Dakota High School Biology Teachers and the Teaching of Evolution and Creationism. American Biology Teacher 51: 275-279.
Williams, G. C. 1992. Natural Selection: Domains, Levels, and Challenges. Oxford University Press, New York.
Zimmerman, M. 1987. The Evolution-Creation Controversy: Opinions of Ohio High School Biology Teachers. Ohio Journal of Science 7: 115-121.
Reprinted with permission from: Paleontological Society
Paleontological Society Papers, Vol. 5, October 1999, The Evolution-Creation Controversy II: Perspectives on Science, Religion, and Geological Education, Edited by Patricia H. Kelley, Jonathan R. Bryan, and Thor A. Hansen