Peppered Moth Again

The peppered moth—widely hailed as “a compelling example of evolution in action”—is back in the news thanks to the posthumous publication of “the last experiment of Michael Majerus.”2 Majerus, an evolutionary biologist, in 1998 wrote Melanism: Evolution in Action, a book in which he suggested “the peppered moth case is fatally flawed as an example of Darwinian evolution.” Majerus was critical of naturalist Bernard Kettlewell’s methodology. Kettlewell’s experiments in the 1950s had given the peppered moth iconic status in evolutionary texts.

A subsequent book review in Nature in which evolutionist Jerry Coyne wrote, “My own reaction resembles the dismay attending my discovery, at the age of six, that it was my father and not Santa who brought the presents on Christmas Eve,”3 really caught media attention. Coyne, summing up his critique, wrote, “Depressingly, Majerus shows that this classic example is in bad shape, and, while not yet ready for the glue factory, needs serious attention.”4

The color of the moth Biston betularia is a fine illustration of Mendelian genetics.

The color of the moth Biston betularia is a fine illustration of Mendelian genetics. The black color of the carbonaria variety is conveyed by a single dominant gene, but the peppered typica form predominated in mid-18th century England. When the Industrial Revolution resulted in soot-covered trees and acid rain destruction of tree lichen, the lighter peppered moth lost its camouflage, contended Kettlewell, and became vulnerable to bird predation. The moth population soon became predominantly black. Once clean air controls were instituted, the population shifted in favor of the peppered variety.

Much of the legitimate criticism of Kettlewell’s classic experiments devolved on the question of whether moths really rest on tree trunks during the day and whether the population shift was related to bird predation. Majerus set out to solve the moth mystery, correcting weaknesses in Kettlewell’s work. Majerus observed 4864 moths during his six-year study. He died before results could be published. Analysis of his data by colleagues published online February 8 in Biology Letters confirms “camouflage and bird predation as the overriding explanation for the rise and fall of melanism in moths.”5

Public distrust of “the prize horse in our stable,”6 as Coyne described the moth tale, unfortunately skyrocketed due to scathing allegations of fraud in Judith Hooper’s book Of Moths and Men: An Evolutionary Tale. (Hooper is not a creationist.) Majerus and others have refuted her allegations. Nevertheless, visually compelling accounts of moths glued to tree-trunks transformed the “textbook example of evolutionary forces in action” into a laughingstock.

From the point of view of biblical creationists, the moth debacle was also unfortunate, though for different reasons.

From the point of view of evolutionists, the moth debacle was unfortunate because it eroded public confidence in the oft-taught assertion that this dramatic example of natural selection supported the notion of molecules-to-man evolution. As evolutionists generally contend, “Macroevolution is simply microevolution writ large: add up enough small changes and we get a large change.”7

From the point of view of biblical creationists, the moth debacle was also unfortunate, though for different reasons. By latching onto the scandalous assertions, some people failed to address the fallacious textbook use of this illustration to support Darwinian evolution. A simple reshuffling of existing genetic information within a created kind (so-called microevolution) is not logically connected to the evolution of new kinds of organisms from lower forms (so-called macroevolution, a process that would require the never-observed acquisition of new genetic information).

Furthermore, creationists pointing to the suspect experiment drew criticism for supposedly denying natural selection occurs. Historically, creationist Edward Blyth published articles describing natural selection in the Magazine of Natural History 22 years before Darwin published his assertions, some of which were lifted almost verbatim from Blyth’s work. We at Answers in Genesis, like most biblical creationists, fully affirm the observable reality and the importance of natural selection (though we submit the term “natural selection” is a poor choice of words to describe the phenomenon; nature does not have a mind and can’t be a “selector”). But natural selection acts only on existing information; it cannot create new genetic information to produce new kinds of organisms. Nevertheless, creationists who question the classic moth model are often falsely accused of denying natural selection.

If the moth population truly shifts in response to change in environmental conditions—which Majerus’s work and another of study8 of similar moths in the polluted northeastern United States suggest—then the peppered moth story is “fine example of natural selection in action.” And with Majerus’s observations now confirming moths really do rest on trunks before sunrise and get gobbled up by birds early in the day, we even know the agent of natural selection, at least in England. But the peppered moth is not and never has been proof of “Darwinian evolution” in the molecules-to-man sense.