Too Bad David Coppedge Isn't a Peppered Moth
If he were, instead of being an intelligent-design advocate, Coppedge would have been reinstated in his job at NASA's Jet Propulsion Lab long ago. Such is the determination on the part of the moth's supporters that no matter how many times you knock it down from its status as an icon of evolution, they keep nailing it right back up there on the fabled tree trunk.
The Scientist seems to still feel a need to do penance for having published an article by Jonathan Wells back in 1999 dismantling the moth story. Nothing about the facts has really changed since then but a new article in the magazine insists on waving the ragged lepidopteran as a newly restored banner of evolution ("Mighty Moth Man").
You know the story, or if you don't then go back and read some of our recent coverage by Dr. Wells. In brief, the original experiments by physician Bernard Kettlewell seemed to show how the predominating color of some British moths changed in response to environmental factors (pollution turning tree trunks darker, predacious birds). It was an illustration, even if a trivial one, of natural selection at work. Evolutionary biologist Michael Majerus demonstrated the faults in Kettlewell's methods, which some have taken to be fraudulent. The main point, though, is that textbook publishers for decades mislead students with photos of the moth resting on tree trunks though most of these photos were phony, having been staged. Wells covers this ground in a chapter in Icons of Evolution.
Even arch-evolutionist Jerry Coyne backed away from the moth. Meanwhile, Majerus did his own experiment, which he felt proved, despite Kettlewell's flawed work, that the point of it was still valid: "It provides after all: The Proof of Evolution." Majerus's proof appeared posthumously, thanks to four colleagues, in Biology Letters back in February ("Selective bird predation on the peppered moth: the last experiment of Michael Majerus").
Somewhat tardily, The Scientist now hails the publication as "restor[ing] the peppered moth to its iconic status as a textbook example of evolution." Jerry Coyne gets a quote where he affirms having re-embraced the insect.
Upon seeing Majerus's results in a peer-reviewed journal, Coyne resumed teaching the peppered moth story after a 14-year hiatus. "He did everything he needed to do to take care of the problems in Kettlewell's experiment," he says.There's something hallucinatory about this fixation on a single pitiable and tattered animal. They cling to it as if the fate of their idea really did depend on those 48 moths -- count them! -- that Majerus observed resting on trunks rather than branches over the length of his seven-year experiment. Jonathan Wells said it here definitively.
Darwinian evolution requires much more than the selection of beneficial traits, and much more than a shift in the proportions of light- and dark-colored moths. It requires the descent with modification of all living things from one or a few common ancestors. Darwin did not write a book titled How the Proportions of Two Pre-existing Moth Varieties Can Change Through Natural Selection; he wrote a book titled The Origin of Species by Means of Natural Selection.If Darwin advocates had something better than the peppered moth, at least something more camera-ready and kid-friendly, wouldn't they just let this one go?
Majerus went on to say that "there are a tremendous number of examples of Darwinian selection in action." And indeed there are: beak changes in Galápagos finches, for one. Natural selection happens; I've never met anyone who doubts it. The question is whether natural selection can produce new species, organs and body plans. This question is not answered by shifts in the proportions of pre-existing varieties of the same species. Even if the camouflage-predation explanation for industrial melanism were undisputed, it would not get us any closer to "proving" Darwinian evolution.