A wing and a prayer

August 8, 2003

Creationists should stick to discourse on religion and leave the peppered moth to get on with evolution, says Michael Majerus

We biologists in Britain have long felt superior to some of our US counterparts because we do not suffer from legislation forcing us to teach creationist creeds in biology. However, our self-satisfaction has now been exploded. As of last year, one local education authority mandated that creationism be taught in British schools as an alternative to evolution to explain the diversity of life. At the root of that decision was a moth.

The peppered moth is the most famous example of Darwinian evolution - the survival of the fittest. It is normally white with a dusting of black speckling. But in 1848, a black, or melanic, form was found in Manchester and spread rapidly in industrial areas. By 1895, 98 per cent of Mancunian moths were black. The following year, the great Victorian lepidopterist J.

W. Tutt theorised that birds found these black moths harder to spot than pale ones on trees denuded of their lichens by sulphur dioxide and darkened by soot. In unpolluted regions, the white form was still better camouflaged and remained predominant. Bernard Kettlewell verified this with his famous bird predation experiments in the 1950s.

For 40 years thereafter, the story of the melanic moth was the example par excellence of Darwinian evolution in action. But over the past five years, its reputation, and that of scientists who worked on it, has been unfairly tarnished.

In 1998, Oxford University Press published my book Melanism: Evolution in Action , which details the complex evolutionary ecology of industrial melanism. Jerry Coyne reviewed the book in the journal Nature . His article was in essence favourable. But Coyne's main message was that "for the time being we must discard the peppered moth as a well-understood example of natural selection in action". I did not recognise this as a review of my book and I had certainly not made such a claim.

Coyne's review, and a follow-up article in The Sunday Telegraph became grist for the creationists' mill. This culminated in last year's publication of Judith Hooper's Of Moths and Men: Intrigue, Tragedy and the Peppered Moth . This book purports to give the untold story of the humble creature's rise to fame. But it does not.

What it gives is an ill-informed, quasi-scientific, subjective potted history of the peppered moth story, undermined throughout by Hooper's relentless, unfounded suspicion of fraud, aimed at Kettlewell and his mentor, E. B. Ford.

The book contains many factual errors, and Hooper demonstrates that she understands little of evolution, and even less about the moth that is her subject. Yet she deems herself capable of providing a more cogent critical assessment of the case than a cohort of evolutionary geneticists and entomologists who have spent years researching the moth. Moreover, she smears the reputations of two dead scientists who cannot defend themselves.

Anti-evolutionists now argue that if the peppered moth story is dead, then Darwinism is too. Nonsense. Evolution is defined as the change in frequency of inherited traits over time. The black peppered moth, which inherited its colouring according to Mendel's laws of genetics, did increase in frequency, and now, following anti-pollution law, is declining.

This is proof of evolution. Furthermore, the speed and direction of the changes can be explained only by natural selection. Hence, proof of Darwinian evolution.

The only question that remains is whether Tutt's bird predation hypothesis is sound. All the experimental work to date suggests that it is.

Kettlewell's work, and eight other independent studies, all point to bird predation as the main factor in the rise and fall of the black peppered moth.

I have studied peppered moths for 40 years, have found more in the wild than any other person alive, and have read more than 200 scientific papers on the case. My conclusion is simple - this is still a perfect illustration of evolution by natural selection.

The earth faces huge problems of overpopulation, diminishing resources, loss of habitats and species extinctions. More than ever before, biologists with an understanding of the complexities of ecological systems are needed.

Darwinian evolution is fact and, as Theodius Dobzhansky famously said, "nothing in biology makes sense except in the light of evolution".

Hooper, and the anti-evolutionists who cite her, should stick to topics they know something about. Their creationist faiths belong in religious education classes, not biology lessons.

Michael Majerus is a reader in evolution at Cambridge University. He spoke on the peppered moth controversy at the Royal Entomological Society's international symposium on evolutionary entomology at Reading University last week.

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