Recently in Peppered Moths Category

wikipedia_peppered_moths.jpgToday a paper came out that should get special attention from evolutionary biologists, evolution educators, and creationism fighters. It is:

Cook, L. M.; Grant, B. S.; Saccheri, I. J.; Mallet, J. (2012). “Selective bird predation on the peppered moth: the last experiment of Michael Majerus.” Biology Letters, Published online before print February 8, 2012. doi: Abstract at Journal, Supplementary Online Material.


Colour variation in the peppered moth Biston betularia was long accepted to be under strong natural selection. Melanics were believed to be fitter than pale morphs because of lower predation at daytime resting sites on dark, sooty bark. Melanics became common during the industrial revolution, but since 1970 there has been a rapid reversal, assumed to have been caused by predators selecting against melanics resting on today’s less sooty bark. Recently, these classical explanations of melanism were attacked, and there has been general scepticism about birds as selective agents. Experiments and observations were accordingly carried out by Michael Majerus to address perceived weaknesses of earlier work. Unfortunately, he did not live to publish the results, which are analysed and presented here by the authors. Majerus released 4864 moths in his six-year experiment, the largest ever attempted for any similar study. There was strong differential bird predation against melanic peppered moths. Daily selection against melanics (s ≃ 0.1) was sufficient in magnitude and direction to explain the recent rapid decline of melanism in post-industrial Britain. These data provide the most direct evidence yet to implicate camouflage and bird predation as the overriding explanation for the rise and fall of melanism in moths.

As long-time readers of Panda’s Thumb know, I’ve had an axe to grind about the peppered moth case since the beginning of my serious involvement with creationism-fighting. Back in 2002 I wrote a long review of Jonathan Wells’s creationism/ID book Icons of Evolution for Wells’s strategy was very clever; rather than attacking the science of evolution head-on, he attacked high school biology textbooks. He engaged in a delicate dance of selective citation and quote-mining so as to make it appear that the criticisms of standard textbook examples used to introduce various evolutionary concepts were coming from scientists.

Peppered Moths: We Told You So


The ID movement hasn’t had many successes, but one area where they did pretty much succeed in causing considerable havoc was the classic textbook example of natural selection in action: the change in color of peppered moths (Biston betularia) from peppered white, to black, and back to peppered white again. Through a series of accidents that is still difficult to understand, the idea got started in the late 1990s that leading peppered moth researcher Michael Majerus had debunked Bernard Kettlewell’s famous study confirming the old hypothesis that the change in peppered moth color was due to selective predation of conspicious moths by birds.

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