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Dr. Jonathan Wells Responded to Answers to His Questions: This is the Peppered Moth Question

A year ago, I posted " Ten Questions To Ask Your Biology Teacher About Evolution ." On November 28, 2001, The National Center for Science Education (NCSE) posted its answers to my questions.

According to the NCSE, many of the claims in my questions "are incorrect or misleading," and they are "intended only to create unwarranted doubts in students' minds about the validity of evolution as good science." It is actually the NCSE's answers, however, that are incorrect or misleading. My original questions (in italics) are posted below; each question is followed by the NCSE's answer (in bold), a brief outline of my response, and then my detailed response. Numbers in parentheses refer to research notes at the end.

My Question: PEPPERED MOTHS. Why do textbooks use pictures of peppered moths camouflaged on tree trunks as evidence for natural selection--when biologists have known since the 1980s that the moths don't normally rest on tree trunks, and all the pictures have been staged?

NCSE's Answer: These pictures are illustrations used to demonstrate a point--the advantage of protective coloration to reduce the danger of predation. The pictures are not the scientific evidence used to prove the point in the first place. Compare this illustration to the well-known re-enactments of the Battle of Gettysburg. Does the fact that these re-enactments are staged prove that the battle never happened? The peppered moth photos are the same sort of illustration, not scientific evidence for natural selection.

My Response in Outline:

(a) The NCSE's first point is technically correct: The textbook pictures are illustrations, not actual evidence.

(b) The NCSE is using this technical point, however, to obscure the real issue: The textbook pictures misrepresent the natural resting-place of peppered moths and conceal serious flaws in the standard story.

(c) Staged peppered moth photos are not comparable to re-enactments of the Battle of Gettysburg, because the former misrepresent the truth.

(d) If using staged photos and re-telling a flawed story "demonstrate a point," as the NCSE claims, the point is that students cannot trust what they read in their biology textbooks.

My Response in Detail:

(a) True, the textbook pictures are illustrations, not actual evidence. It would have been more accurate for me to write "examples of" or "illustrations of" instead of "evidence for."

(b) The NCSE uses this technical point, however, to obscure the fact that textbook pictures misrepresent the evidence and conceal serious flaws in the peppered moth story. Two hundred years ago, almost all peppered moths in the U.K. were light-colored. During the industrial revolution, dark-colored moths became much more common--especially in the polluted woodlands around major cities. According to theory, the shift occurred because dark-colored moths were better camouflaged against pollution-darkened tree trunks, and thus less likely to be eaten by predatory birds. In the 1950s, Bernard Kettlewell released light and dark-colored moths onto nearby tree trunks in polluted and unpolluted woodlands, and watched as birds ate the more visible ones. The story, and Kettlewell's experiments, became the classic textbook example of natural selection. When pollution-control legislation resulted in cleaner air after the 1950s, light-colored moths became more common again, as the theory predicted. Contrary to the theory, however, this occurred BEFORE tree trunks reverted to their former light color. In the 1980s, biologists discovered that peppered moths don't normally rest on tree trunks, and many began to question the classic story about camouflage and bird predation. In 1998, Theodore Sargent, Craig Millar and David Lambert wrote in Evolutionary Biology: "There is little persuasive evidence...to support this explanation at the present time." And as University of Chicago evolutionary biologist Jerry Coyne wrote in Nature, the fact that peppered moths do not normally rest on tree trunks "alone invalidates Kettlewell's experiments, as moths were released by placing them directly onto tree trunks." (14)

(c) The NCSE's comparison of staged peppered moth photos with re-enactments of the Battle of Gettysburg is inappropriate, because the former misrepresent the facts. The appropriate comparison would be with FALSE re-enactments of the Battle of Gettysburg--such as re-enactments staged in Chancellorsville (where the other side won). Scientific illustrations, like historical re-enactments, should portray the truth.

(d) Instead of telling students the truth about peppered moths, most biology textbooks repeat the classic story and illustrate it with staged pictures--many of them made by pinning or gluing dead moths to tree trunks. For example, Johnson's Biology: Visualizing Life (1998), Guttman's Biology (1999), Schraer and Stoltze's Biology: The Study of Life (7th Edition, 1999), and Miller and Levine's Biology (5th Edition, 2000) all use staged photos and summaries of Kettlewell's experiments to convince students that peppered moths are a classic demonstration of natural selection in action. Mader's Biology (6th Edition, 1998) goes even further, using Kettlewell's experiments as the paramount example of how to do science: "The scientific method consists of forming a hypothesis, testing it, and coming to an conclusion...In order to examine the scientific method in more detail, we will consider research performed by British scientist H.B.D. Kettlewell." If these illustrations "demonstrate a point," as the NCSE claims, the point is that students cannot trust what they read in their biology textbooks. (15)

(14) Theodore D. Sargent, Craig D. Millar and David M. Lambert, "The "Classical" Explanation of Industrial Melanism: Assessing the Evidence," Evolutionary Biology 30 (1998), 299-322, pp. 318; Jerry A. Coyne, "Not black and white," a review of Michael Majerus's Melanism: Evolution in Action, Nature 396 (1998), 35-36. See also Jonathan Wells, "Second Thoughts about Peppered Moths," The Scientist (May 24, 1999), 13.

(15) The relevant page numbers in the cited textbooks are: Johnson's Biology: Visualizing Life (1998), p. 182; Guttman's Biology (1999), pp. 35-36; Schraer and Stoltze's Biology: The Study of Life (7th Edition, 1999), pp. 618-619; Miller and Levine's Biology (5th Edition, 2000), pp. 297-298; Mader's Biology (6th Edition, 1998), pp. 11-12, 306.

http://www.discovery.org/a/1106