In the late 1990s, questions were raised about some of Kettlewell’s scientific techniques, such as his placing of moths on tree trunks, where they had not frequently been observed to settle naturally. This led some people to doubt whether the evolution of the moths happened as had been described.
The criticism began when Professor Majerus, at the University Of Cambridge Department Of Genetics published Melanism: Evolution in Action in 1998, to mark the 25th anniversary of the release of Kettlewell's books on melanism. A quarter of the book deals with the peppered moth and brings the story up to date while summarising the facts and methods of the study as well as the criticisms against it. Majerus discusses problems in Kettlewell’s original experiments such as ‘Bird table effects’: the release of moths in unnatural sites at unnatural frequencies at unnatural times of the day, and the use of lab reared and wild caught specimens. These factors would individually tarnish the conclusions drawn by Kettlewell and Majerus rightly pointed this out. Indeed, the case would not be as strong were it not for subsequent studies that avoided one or more of these sources of artificiality but drew the same conclusions.
One reviewer of the book was less convinced. In his review entitled ‘Not Black and White’, American geneticist Jerry Coyne wrote a comment that sparked a series of articles in the popular press. He concluded that ‘for the time being we must discardBiston as a well understood example of natural selection in action, although it is clearly a case of evolution’. Articles that followed included ‘scientists pick holes in Darwin moth theory’, ‘Darwinism in a flutter’, ‘the moth that failed’ and 'moth eaten statistics'. Despite other positive reviews, including one slating the accuracy of Coyne’s original paper, the fuss it made was picked up by the anti-evolution lobby. With the aim of trashing the peppered moth as an example of evolution in action, the lobby promoted the claim that evolution as a whole was unsupported and wrong; perhaps reading Coyne’s quote above as 'for the time being we must discard Biston as a example of natural selection'. Note the difference!
Adding fuel to the fire, Judith Hooper, a science-journalist wrote Of Moths and Men: Intrigue, Tragedy and the Peppered Moth, a story about “fraud, deceit and self-driven ambition” based on supposed coded messages between Kettlewell and his supervisor Ford. Hooper’s tale promotes the notion that the peppered moth story was based on ‘data fudging’ and suggests a serious flaw in the study by neglecting predation by bats. This of course went down a storm with the anti-evolutionists and the popular media. However her book, which on the cover claimed to be ‘a riotous story of ambition and deceit’, was widely criticised by the scientific community. This included Coyne who states that Hooper ‘unfairly smears a brilliant naturalist’ and ‘has done the scientific community a disservice’.
During the period that the peppered moth case was under attack, Majerus devised a series of experiments to verify Kettlewell’s original findings and address the criticisms made against the case. This work was to take him over seven years. His methods allowed experimentation in the wild using natural densities of Biston released in their natural resting position at dusk and at the time of year they are active, and he compared results obtained using lab reared and caught moths. He addressed all the major criticisms made and even carried out an experiment comparing rates of bat predation on the different forms to test Hooper’s claim that bats and not birds were the most important predators.
Majerus’ results showed that, unsurprisingly, bats (which use sound not sight in their hunting) do not show differential selection of either form. He identified the natural resting site of the moths and definitively showed that, in his unpolluted test-site, a significantly greater proportion of carbonaria were eaten by birds than typical, and that typical is increasing in numbers. Differential predation by birds was sufficient to drive changes in the frequencies of the two forms. Majerus’ data therefore confirms Kettlewell’s experiments and re-affirms the peppered moth as a text book case of evolution in action.
But why should we be interested in the peppered moth story? As a very widely known example of evolution, one which even those with little experience in the field will probably know of, it is an obvious choice for the anti-evolution lobby to attack. Majerus' motivation for undertaking such a mammoth project was to be able to say with authority whether the peppered moth should be taught in schools as an example of Darwinian evolution in action. The peppered moth story is so easy to understand and involves elements school students can related to. In Prof. Majerus’ words 'that is why the anti-evolution lobby attacks the peppered moth story. They are frightened that too many people will be able to understand'.