According to Professor Steve Jones of University College, London: 

"Evolution's best evidence is from a revolution; the Industrial  Revolution that polluted much of England. The nation's moths turned black as birds ate those whose genes made them conspicuous against sooty trees. With smoke control, the story  worked in reverse, and now the black moths are down to a fraction of what they once were." Daily Telegraph, Feb 10, 1999, page 16.

However, the Peppered Moth story, one of the most important evidences used to support Darwinian evolution in popular textbooks, is widely recognised to be seriously flawed. Instead of the research providing a convincing study of natural selection in action, it is now regarded as a case of unnatural selection.

Every student of evolutionary theory is aware of Kettlewell's 1950's research work in England involving the Peppered Moth. This moth exhibits melanism: it has a dark form as well as its normal light form. Kettlewell's contribution was to provide reasons for changes within the population from light to dark in areas associated with industrial pollution in the early part of the Century

In brief, the research identified birds as the agents of natural selection, as they discovered moths resting on the trunks of trees. In areas with light coloured trunks, the light moths predominated (with dark moths being selectively eaten by birds) and in areas with dark trunks (affected by industrial pollution) the dark moths predominated (with light moths being the prime target for predation). The story is simple and people have found it compelling. It rapidly became the prime example of natural selection, and an essential case study illustrating a key concept in Darwinian evolution.

Biologists have numerous other examples of organisms evidencing variation, but the drivers of variation have not been at all easy to identify. The Peppered Moth story was welcomed because it identified the selection forces affecting a population of an organism. Kettlewell himself was proud of this achievement and he entitled a 1959 article in Scientific American as "Darwin's missing evidence"

This story is subjected to critical study in Melanism: evolution in action, by Michael Majerus, Oxford University Press (1998). Not much of Kettlewell's interpretation survives! When left to themselves, the moths do not normally settle on tree trunks and "a concerted effort to obtain a substantial data set showing where peppered moths normally rest in the wild is urgently needed" (p.125). Furthermore, it is not confirmed that bird predation is significant (although Majerus suspects it is): "although observations of peppered moths being taken from natural resting positions are still lacking and are urgently needed, it is highly probable that predation levels are significant"(p.125). There is no satisfactory evidence that moths choose matching backgrounds on which to settle (Kettlewell's findings have not been replicated by other scientists. Majerus writes: "the issue of whether and how the forms of peppered moth select appropriate resting positions is fraught with controversy and full of contradictory evidence" (p.140)). It has never been shown that the probability of a moth being eaten by birds is related to the extent to which the moth is well camouflaged. "Experiments to show formally that the degree of crypsis of the different peppered moth forms does affect the level of predation inflicted upon them by birds have never been carried out" (p.125). Increases and decreases in numbers of the melanic form have been observed in other areas. In the Netherlands, there is some correlation with industrial pollution and environmental recovery, but in the USA there have been large changes in the frequencies of the dark form without corresponding changes in tree colour (p.149). The Peppered Moth must therefore join the ranks of many (if not all!) other examples of natural variation in which the causes are either unknown or are very poorly understood.

Majerus says that "the case of the peppered moth is undoubtedly more complex and fascinating than most biology textbooks have space to relate" (p.155). However, he offers his personal view that "differential bird predation in more or less polluted regions, together with migration, are primarily responsible, almost to the exclusion of other factors" (p.155). This view was not shared by Professor Jerry Coyne, who reviewed Majerus' book for Nature, 396, 35 - 36 (1998). Coyne wrote: 

"From time to time, evolutionists re-examine a classic experimental study and  find, to their horror, that it is flawed or downright wrong. …Until now, however, the prize horse in our stable of examples has been the evolution of 'industrial melanism' in the peppered moth, Biston betularia, presented by most teachers and textbooks as the paradigm of natural selection and evolution occurring within a human lifetime. The re-examination of this tale is the centrepiece of Michael Majerus's book, Melanism:  Evolution in Action. Depressingly, Majerus shows that this classic example is in bad  shape, and, while not yet ready for the glue factory, needs serious attention…."


"Majerus concludes, reasonably, that all we can deduce from this story is that it is a case of rapid evolution, probably involving pollution and bird predation. I would, however, replace "probably" with "perhaps". B. betularia shows the footprint of natural selection, but we have not yet seen the feet. Majerus finds some solace in his analysis, claiming that the true story is likely to be more complex and  therefore more interesting, but one senses that he is making a virtue of necessity. 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."

In a report for the Sunday Telegraph (14 March 1999), Robert Matthews quotes Coyne as saying that Dr Kettlewell's widely-quoted experiments are essentially useless: "There is a lot of wishful thinking and design flaws in them, and they wouldn't get published today." Matthews adds his own assessment of the situation: 

"Experiments using the moth in the Fifties and long believed to prove the truth of natural selection are now thought to be worthless, having been designed to come up with the "right" answer. Scientists now admit that they do not know the real explanation for the fate of Biston betularia, whose story is recounted in almost every textbook on evolution."

The basic problems with Kettlewell's work have been recognised by specialists for at least 10 years, yet the popularisers of evolution have been reluctant to drop the Peppered Moth as their prime example of evolution in action. Specialists have known for years that Peppered Moths do not naturally settle on tree trunks, yet the popularisers have continued to promote a story based on Kettlewell's day-time releases of disoriented moths which were designed to get them to settle on tree trunks where (unnatural) predation could be observed. Specialists have failed to find evidence for the moths naturally choosing a matching background on which to settle - yet Kettlewell's positive results on this have continued to be regarded as valid.

Why has there been such a reluctance to take on board more recent research? The answer would appear to be that Darwinian evolutionists have an agenda much broader than "scientific" understanding. Their agenda is ideological: a conviction that origins must be explained in terms of natural causes. The tenets of Darwinism have their roots in philosophy rather than science. According to Darwinists, natural selection has to be a powerful force that winnows the variations that are thrown up by the process of reproduction, thereby giving the illusion of design in living things. However, is natural selection really so powerful? Actually, it is extremely difficult to identify selective forces and to trace adaptations emerging in a population of animals or plants. As a result, the "just-so" stories of Darwinism (purporting to explain how the eye developed, or flight, etc) should be viewed as the dreaming of ideologues rather than the conclusions of scientists.

It is worth pondering why the myth has been perpetuated. Darwinists generally present themselves as models of scientific integrity, yet here is a case where the self-correcting nature of science has not been working well. Darwinists badly need the Peppered Moth story: there is still the problem of "Darwin's missing evidence"! Christians, however, do not need to force the data so that it fits our pet theories. We are free to question the remarkable powers attributed to natural selection.

Judging by the popular press, the Peppered Moth legend is going to stay around for some time. In a recent article on lichens in the Independent on Sunday , ("The lichen are coming - thanks to Britain's cleaner air", May 2, 1999, page 9), Steve Connor, the Science Editor writes: 

"Rare species of lichen which have disappeared from much of Britain are making a dramatic comeback thanks to cleaner air. … The demise of lichen-covered trees in  Victorian Britain was responsible for a famous case of evolution in action - the demise of  the mottled form of the peppered moth in favour of its black, melanic mutant. Scientists  found that the mottled form was perfectly camouflaged against predators when resting on a  lichen-covered tree. When lichens disappeared, it was the relatively rare melanic form  that had a better chance of not being seen by birds."

Why is this version of the legend wrong? (a) The link between industrial melanism and the camouflage provided by lichen cover is not one that has been confirmed by scientific research. (b) Bird predation is inferred (but not confirmed) as the major cause of selection. (c) To describe this as an example of "evolution in action" is completely unwarranted. Evolutionary theories cannot be allowed to have a monopoly on permissible interpetations! We are seeing here an example of variation in nature - a characteristic that God has designed to bring robustness to ecosystems and which facilitates the survival of the organisms he has created. Natural selection is a key element of ecological thinking - but only dogma extrapolates its relevance to the realm of origins.

David J. Tyler (June 1999)

Related Links:
Second thoughts about Peppered Moths by Jonathan Wells. (The Scientist, 13(11), p.13. May 24 1999) Expanded version (February 9, 2001)
Second thoughts about Peppered Moths by Jonathan Wells. (The True-Origins Archive, April 1999)
Second Thoughts about Peppered Moths by Jonathan Wells ARN documents, Dated April 6, 1999

Return to top of page