Welcome Article on Natural Selection in Peppered Moths

David W. Rudge (2005), assistant professor of biological sciences at Western Michigan University, has published a very welcome addition to the literature regarding Bernard Kettlewell’s classic experiments on natural selection in peppered moths. Here are some of his comments regarding his concerns about creationists’ misuse of industrial melanism and of Judith Hooper’s charges of fraud against Kettlewell:

As one might imagine, advocates of creation and intelligent design have misinterpreted these long-recognized problems as undermining the continued use of the example in science textbooks (Wells 2000; but see also Rudge 2002). The motive in these attacks is transparent: if one can knock down the poster child of evolution, the entire theory will thereby become suspect. As noted above, the continued inclusion of the phenomenon of industrial melanism in textbooks should not be interpreted as an indication of its theoretical importance to evolutionary biology. Moreover, no one should be surprised that there are differences between the explanations given in popularizations and introductory textbooks, which are intended for children and the lay public, and what is actually known about the phenomenon as it is discussed in journal articles intended for scientists. The existence of ongoing questions about the phenomenon is indicative of an active area of research. That scientists continue to believe the explanation we associate with Kettlewell does not imply they are being dogmatic in the face of overwhelming contradictory evidence. Biologists don't abandon well-supported theories simply because they run into problems applying an idealized explanation to a particular example, particularly when no better alternative theory is available. Moreover, even if we threw out Kettlewell's experimental work on bird predation entirely, it wouldn't threaten in any way the enormous genetic evidence for natural selection in the evolution of melanism, nor the eight or so follow-up predation studies on the mechanism that qualitatively support Kettlewell's original conclusions (Cook 2000, 2003). 

Similar discrepancies surround our current understanding of Kettlewell’s work on the phenomenon. In the first book-length popularization of this episode, Judith Hooper (2002) portrays Kettlewell as a bumbling amateur and all but accuses him of committing fraud. The latter charge is entirely baseless (Grant 2002, Rudge 2005). No one would deny that, judged by contemporary standards, the design and conduct of Kettlewell’s experiments are problematic (Shapiro 2002). Nor would even Kettlewell deny that his work on the subject involved a number of false steps and errors of interpretation: his first scientific publication of the results of his study is remarkably candid about the numerous problems he encountered in the field (Kettlewell 1955). But do these considerations imply that Kettlewell’s experiments should no longer be used in science classrooms? The answer, I believe, is a decided no. Discrepancies between the textbook accounts of Kettlewell’s work and what scientists now know about it represent a beautiful opportunity for science instructors to help students appreciate a variety of issues associated with the nature of science, such as the tentative nature of scientific conclusions (Rudge 2000, 2004a, 2004b).

Professor Rudge promises an additional article, ‘Did Kettlewell Commit Fraud? Re-examining the Evidence’ (Rudge, 2005b).


Rudge, David, 2005a, ‘The Beauty of Kettlewell’s Classic Experimental Demonstration of Natural Selection,’ BioScience, 55(4), 369-375, http://www.rednova.com/news/display/?id=145150&source=r_science, accessed 1 May 2005.

Rudge, David, 2005b, ‘Did Kettlewell Commit Fraud? Re-examining the Evidence,’ Public Understanding of Science, forthcoming.

Additional bibliography.

Young, Matt, 2005, ‘Why the Peppered Moth Remains an Icon of Evolution,’ The Panda’s Thumb, http://www.pandasthumb.org/pt-archives/000886.html, accessed May 1, 2005.

Young, Matt, and Ian Musgrave, 2005, ‘Moonshine: Why the Peppered Moth Remains an Icon of Evolution,’ Skeptical Inquirer, March-April, pp. 23-28, http://www.csicop.org/si/? (not available on the Web as of this writing).

Further references may be found in (Rudge 2005a).