OF MOTHS AND MEN

Knowledgeable freelance journalist Hooper (Would the Buddha Wear a Walkman?, 1990) shoots down an icon of evolution in action—in a well-written account of the life and times of the peppered moth and the eccentric lepidopterists who chased it.

De rigueur in biology textbooks for a generation is the story of Biston betularia, a moth that appeared in a typical peppery gray form and in a black version. The alternate form paralleled the rise in England of the industrial revolution, during which pollutants spread to woodlands near factory towns. The surmise by latter-day Darwinists was that a gene for blackness had appeared or been turned on, allowing black moths to be camouflaged on soot-coated tree trunks and avoid predation by birds, while in nonpolluted areas the peppery form remained predominant, concealed against lichen-coated barks. This theory became an idée fixe in the minds of Oxford polymath moth-man E.B. Ford and his field researcher, rugged physician H.B.D. Kettlewell, who laid out marked numbers of moths in both forms on tree trunks, set traps to recapture the moths, and counted which ones survived. Invariably, the blacks did well in polluted areas and vice versa elsewhere. There was no question that Kettlewell was a superb field naturalist, but did the “proofs” he and Ford published have any basis in reality? Statistically, the data was almost too good, and in due course the pair’s tactics were questioned. Far too many moths were laid out, stated critics; birds might not be the moths’ chief predators (but knew a good food thing when they saw it); moths actually preferred to hang on the underside of branches, and so on. Eventually, Kettlewell, suffering from back pain, humiliation, personal slights, and depression, committed suicide. Ford outlived him and remained a diehard adaptationist to the end. The mystery of why black forms appeared when they did remains unsolved.

By no means anti-evolutionary fodder for creationists, but rather a cautionary tale of how science gets done—and undone.