As stated in The American Biology Teacher by the eminent scientist Theodosius Dobzhansky (1973), "Nothing in biology makes sense except in the light of evolution." This often-quoted assertion accurately illuminates the central, unifying role of evolution in nature, and therefore in biology. Teaching biology in an effective and scientifically-honest manner requires classroom discussions and laboratory experiences on evolution.

Modern biologists constantly study, ponder and deliberate the patterns, mechanisms and pace of evolution, but they do not debate evolution's occurrence. The fossil record and the diversity of extant organisms, combined with modern techniques of molecular biology, taxonomy and geology, provide exhaustive examples and powerful evidence for genetic variation, natural selection, speciation, extinction and other well-established components of current evolutionary theory. Scientific deliberations and modifications of these components clearly demonstrate the vitality and scientific integrity of evolution and the theory that explains it.

This same examination, pondering and possible revision have firmly established evolution as an important natural process explained by valid scientific principles, and clearly differentiate and separate science from various kinds of nonscientific ways of knowing, including those with a supernatural basis such as creationism. Whether called "creation science," "scientific creationism," "intelligent-design theory," "young-earth theory" or some other synonym, creation beliefs have no place in the science classroom. Explanations employing nonnaturalistic or supernatural events, whether or not explicit reference is made to a supernatural being, are outside the realm of science and not part of a valid science curriculum. Evolutionary theory, indeed all of science, is necessarily silent on religion and neither refutes nor supports the existence of a deity or deities.

Accordingly, the National Association of Biology Teachers, an organization of science teachers, endorses the following tenets of science, evolution and biology education:

• The diversity of life on earth is the outcome of evolution: an unpredictable and natural process of temporal descent with genetic modification that is affected by natural selection, chance, historical contingencies and changing environments.
• Biological evolution refers to changes in populations, not individuals. Changes must be successfully passed on to the next generation. This means evolution results in heritable changes in a population spread over many generations. In fact, evolution can be defined as any change in the frequency of alleles within a gene pool from one generation to the next.
• Evolutionary theory is significant in biology, among other reasons, for its unifying properties and predictive features, the clear empirical testability of its integral models and the richness of new scientific research it fosters.
• The fossil record, which includes abundant transitional forms in diverse taxonomic groups, establishes extensive and comprehensive evidence for organic evolution.
• Natural selection, the primary mechanism for evolutionary changes, can be demonstrated with numerous, convincing examples, both extant and extinct.
• Natural selection—a differential, greater survival and reproduction of some genetic variants within a population under an existing environmental state—has no specific direction or goal, including survival of a species.
• Adaptations do not always provide an obvious selective advantage. Furthermore, there is no indication that adaptations—molecular to organismal—must be perfect: adaptations providing a selective advantage must simply be good enough for survival and increased reproductive fitness.
• The model of punctuated equilibrium provides another account of the tempo of speciation in the fossil record of many lineages: it does not refute or overturn evolutionary theory, but instead adds to its scientific richness.
• Evolution does not violate the second law of thermodynamics: producing order from disorder is possible with the addition of energy, such as from the sun.
• Although comprehending deep time is difficult, the earth is about 4.5 billion years old. Homo sapiens has occupied only a minuscule moment of that immense duration of time.
• When compared with earlier periods, the Cambrian explosion evident in the fossil record reflects at least three phenomena: the evolution of animals with readily-fossilized hard body parts; Cambrian environment (sedimentary rock) more conducive to preserving fossils; and the evolution from pre-Cambrian forms of an increased diversity of body patterns in animals.
• Radiometric and other dating techniques, when used properly, are highly accurate means of establishing dates in the history of the planet and in the history of life.
• Recent findings from the advancing field of molecular genetics, combined with the large body of evidence from other disciplines, collectively provide indisputable demonstration of the theory of evolution.
• In science, a theory is not a guess or an approximation but an extensive explanation developed from well-documented, reproducible sets of experimentally-derived data from repeated observations of natural processes.
• The models and the subsequent outcomes of a scientific theory are not decided in advance, but can be, and often are, modified and improved as new empirical evidence is uncovered. Thus, science is a constantly self-correcting endeavor to understand nature and natural phenomena.
• Science is not teleological: the accepted processes do not start with a conclusion, then refuse to change it, or acknowledge as valid only those data that support an unyielding conclusion. Science does not base theories on an untestable collection of dogmatic proposals. Instead, the processes of science are characterized by asking questions, proposing hypotheses, and designing empirical models and conceptual frameworks for research about natural events.
• Providing a rational, coherent and scientific account of the taxonomic history and diversity of organisms requires inclusion of the mechanisms and principles of evolution.
• Similarly, effective teaching of cellular and, molecular biology requires inclusion of evolution.
• Specific textbook chapters on evolution should be included in biology curricula, and evolution should be a recurrent theme throughout biology textbooks and courses.
• Students can maintain their religious beliefs and learn the scientific foundations of evolution.
• Teachers should respect diverse beliefs, but contrasting science with religion, such as belief in creationism, is not a role of science. Science teachers can, and often do, hold devout religious beliefs, accept evolution as a valid scientific theory, and teach the theory's mechanisms and principles.
• Science and religion differ in significant ways that make it inappropriate to teach any of the different religious beliefs in the science classroom.

Opposition to teaching evolution reflects confusion about the nature and processes of science. Teachers can, and should, stand firm and teach good science with the acknowledged support of the courts. In Epperson v. Arkansas (1968), the U.S. Supreme Court struck down a 1928 Arkansas law prohibiting the teaching of evolution in state schools. In McLean v. Arkansas (1982), the federal district court invalidated a state statute requiring equal classroom time for evolution and creationism.

Edwards v. Aguillard (1987) led to another Supreme Court ruling against so-called "balanced treatment" of creation science and evolution in public schools. In this landmark case, the Court called the Louisiana equal-time statute "facially invalid as violative of the Establishment Clause of the First Amendment, because it lacks a clear secular purpose." This decision—"the Edwards restriction"—is now the controlling legal position on attempts to mandate the teaching of creationism: the nation's highest court has said that such mandates are unconstitutional. Subsequent district court decisions in Illinois and California have applied "the Edwards restriction" to teachers who advocate creation science, and to the right of a district to prohibit an individual teacher from promoting creation science in the classroom.

Courts have thus restricted school districts from requiring creation science in the science curriculum and have restricted individual instructors from teaching it. All teachers and administrators should be mindful of these court cases, remembering that the law, science and NABT support them as they appropriately include the teaching of evolution in the science curriculum.

References and Suggested Reading

Aguillard, D. (1999). Evolution education in Louisiana public schools: a decade following Edwards v. Aguillard. The American Biology Teacher, 61, pp. 182-188.

Brack, A. (Ed.). (1999). The Molecular Origins of Life: Assembling Pieces of the Puzzle. Cambridge: Camnbridge University Press.

Futuyma, D. (1986). Evolutionary biology, 2nd ed. Sunderland, MA: Sinauer Associates, Inc.

Futuyma, D. (1995). Science on Trial. Sunderland, MA: Sinauer Associates, Inc.

Gillis, A. (1994). Keeping creationism out of the classroom. Bioscience, 44, pp. 650-656.

Gould, S. (1994, October). The evolution of life on earth. Scientific American, 271, pp. 85-91.

Gould, S. (1995). Dinosaur in a Haystack. Reflections in Natural History. New York: Harmony Books.

Kiklas, K. (1997). The Evolutionary Biology of Plants. Chicago: The University of Chicago Press.

Matsumura, M. (Ed.). (1995). Voices for Evolution. Berkeley, CA: The National Center for Science Education.

Mayr, E. (1991). One Long Argument: Charles Darwin and the Genesis of Modern Evolutionary Thought. Cambridge, MA: Harvard University Press.

Moore, J. (1993). Science as a Way of Knowing—The Foundations of Modern Biology. Cambridge, MA: Harvard University Press.

Moore, R. (1999). Creationism in the United States: VII. The Lingering Threat. The American Biology Teacher, 61, pp. 330-340. See also references therein to earlier articles in the series.

National Academy of Sciences. (1998). Teaching About Evolution and the Nature of Science. Washington, DC: National Academy Press.

National Academy of Sciences. (1999). Science and creationism—A View from the National Academy of Sciences. Washington, DC: National Academy Press.

National Center for Science Education. P.O. Box 9477, Berkeley, CA 94709. Numerous publications such as Bartelt, K. (1999), A Scientist Responds to Behe's Black Box.

National Research Council. (1996). National Science Education Standards. Washington, DC: National Academy Press.

Pennock, R.T. (1999). Tower of Babel: The Evidence Against the New Creationism. Cambridge, MA: MIT Press.

Weiner, J. (1994). The Beak of the Finch—A Story of Evolution in our Time. New York: Alfred A. Knopf.

Wilson, E. (1992). The Diversity of Life. New York: W.W. Norton & Co.