Evolution Under Pressure a Look at the Controversy About Industrial Melanism in the Peppered Moth

book reviews Evolution under pressure A look at the controversy about industrial melanism in the peppered moth.

Of Moths and Men: Intrigue, conspiracy theory. Her evidence rests largely Tragedy and the Peppered Moth on the fact that Kettlewell’s first experiment by Judith Hooper began as a failure, for he recaptured too few Fourth Estate: 2002. 397 pp. £15.99 moths to show differential survival. His Jerry A. Coyne forlorn letter to Oxford provoked a soothing response from Ford: “It is disappointing A colleague described the physician and that the recoveries are not better… However, naturalist Bernard Kettlewell as “the best I do not doubt that the results will be very naturalist I have ever met, and almost the worth while.” worst professional scientist I have ever To a professional biologist this sounds known”. And yet Kettlewell became one of familiar; many of us have offered similar the best-known evolutionary biologists, for consolation to students having a hard time his work produced the canonical example in the field. But to Hooper, Ford’s note is a of evolution in action: industrial melanism coded message telling Kettlewell to get the in the peppered moth (Biston betularia). In right results at all costs. Sure enough, Kettle- Of Moths and Men, the science journalist well’s recapture rate shot up, perhaps Judith Hooper produces a lively history because he tripled the number of moths of this work, illustrated with fascinating released. Hooper, however, finds this cause but disturbing portraits of the principals. insufficient. Using meteorological records, These include the ambitious but insecure she rules out a change in the weather, and Kettlewell, ill at ease in the rarefied atmos- suggests that the increased recapture rate phere of Oxford University, and his mentor reflected chicanery by Kettlewell — perhaps E. B. Ford, a foppish, manipulative man he changed the experimental design in mid- who used and misused Kettlewell in his own stream, or even mis-scored the moths. But quest for fame. Hooper contends that the Bernard Kettlewell was an enthusiastic naturalist many factors other than the weather can Biston story is not only wrong, but probably who loved to surround himself with his work. change recapture rates, including experi- fraudulent. mental modifications, such as relocating The scientific facts are familiar to biolo- melanism offered Ford and Kettlewell an moth traps, that are completely innocuous. gists. The normal form of B. betularia unparalleled chance to document and under- Anyone with experience of fieldwork knows (known as typica) is white, speckled with stand natural selection in the wild. Ford how unpredictable such experiments can be. dark markings. In around 1850, a melanic, suggested, on the basis of breeding experi- It has been widely recognized that Kettle- all-black form produced by a dominant ments, that carbonaria was more resistant well’s experiments were indeed flawed. mutation (carbonaria) became more numer- than typica to pollution, and hence survived Hooper enumerates the familiar problems: ous in England, at the same time as a rise better. As a naturalist, Kettlewell believed Kettlewell used mixtures of wild-caught and in industrial pollution. By 1900, carbonaria that selection might be due to sharp-eyed lab-reared moths, released them at the reached a frequency of nearly 100% in birds that preyed on the moths that were wrong time of day onto unnatural resting manufacturing areas such as most conspicuous in their local habitat. places, and so on. As a result, Birmingham. There was a Kettlewell tested his hypothesis in 1953. the role of bird predation in parallel increase in indus- After releasing marked typica and carbonaria the evolution of melanism trial areas of the United in a wood where trees were darkened by pol- remains unclear. But slop- States, although somewhat lution, he recaptured a much higher percent- piness is not fraud. Eager later. These evolutionary age of dark than light moths, implying to push her theme of changes were reversed in selective predation on typica. Two years later, “ambitious scientists the middle of the century he obtained the opposite result in an unpol- who will ignore the when antipollution laws luted forest. Combined with observations of truth for the sake of BRISTOL CITY MUSEUM/NATUREPL BRISTOL took effect, and typica the hunting behaviour of birds, and of the fame and recogni- once again became distribution of the two forms in Britain, tion”, she unfair- predominant both in these experiments seemed to provide Dar- ly smears a Britain and in the win’s ‘missing evidence’: a complete story brilliant nat- United States. connecting ecological forces to evolutionary uralist. The rise of change. Kettlewell gained instant fame, and the Biston story was quickly installed in biol- ogy textbooks, where it remains to this day. Light Hooper suggests, however, that the work? release experiments were The two probably fudged to forms of the achieve the desired peppered moth outcome. Unfortu- make it ideal nately, in her desire for studies of to write a lepidopteran evolution. ‘whodunnit’, she advances a flimsy

Competition between women A Mind of Her Own: The Evolutionary Psychology of Women by Anne Campbell Oxford University Press: 2002. 402 pp. £21.99, $40 Elizabeth Cashdan This provocative book argues that competition among women has been an important, yet largely ignored, force in human sexual selection. Competition between males is usually thought to be more intense than female competition because greater male variance in reproductive success means that men are playing for higher stakes. But Campbell suggests that this is misleading: “The variance may not be as great as between males but that is irrelevant because females are not in competition with males, they are in competition with other females.” Mothers (not fathers) are critical to offspring survival, and differences among women in their success in this endeavour have shaped the way that women think, feel and behave. The book opens with a sharp and satis- Kept in captivity fying critique of postmodernist biophobia Lionesses Pacing in a Cage by Max Slovegt depicts Gardens in the West by Eric Baratay and and a skilful rebuttal to those who distrust the experience of wild animals put on public Elisabeth Hardouin-Fugier (Reaktion Books, evolutionary psychology’s scientific meth- display. From Zoo: A History of Zoological £28, $40), recently translated from French. ods and fear its political implications. It closes with an excellent in-depth account Many of the problems with Kettlewell’s for example), mar the book for biologists. of the evolutionary reasons for individual experiments and the ‘classic’ Biston story The biggest shortcoming, however, is variation. In between, Campbell shows us were first aired by the US biologist Ted Hooper’s failure to emphasize that, despite how and why women compete. Sargent. Curiously, when turning from arguments about the precise mechanism of Women are clearly less physically aggres- Kettlewell to Sargent, Hooper’s criticality selection, industrial melanism still repre- sive and less risk-prone than men, but why? evaporates. She claims that Sargent’s criti- sents a splendid example of evolution in Campbell rejects the belief that it is a “default cisms of the moth work ruined his career by action. The dramatic rise and fall of the option that results from lower incentives making him a pariah, rejected by a scientific frequency of melanism in Biston betularia, for competition” and attributes it instead to establishment enamoured with Biston. But occurring in parallel on two continents, is women’s greater parental investment: they this is hyperbole. Sargent’s career may have a compelling case of evolution by natural have more to lose from violent and risky languished because he often published in selection. No force other than selection behaviour. This behavioural difference, little-known journals or (as Hooper notes) could have caused such striking and direc- she argues, is mediated by a sex difference refused to apply for grants — the kiss of tional change. Hooper’s grudging admis- relating to fear of injury and a neuro- death for a US scientist. sion of this fact occupies but one sentence: chemistry that makes women better able to Hooper also champions Sargent’s view “It is reasonable to assume that natural inhibit aggressive impulses. that industrial melanism was a case not of selection operates in the evolution of the These arguments are extended in evolution but of “phenotypic induction” — peppered moth.” Campbell’s discussion of sex differences in a developmental change in the colour of This issue matters, at least in the United dominance and status-seeking. The rewards moths, presumably caused by the larval States, because creationists have promoted of high status “are just as great for females ingestion of pollutants. But she conveniently the problems with Biston as a refutation of as for males — arguably greater because glosses over the simple and unassailable evolution itself. Even my own brief critique resources fuel the survival of offspring in fact that the light and dark alleles of of the story (Nature 396, 35–36; 1998) which they have already invested while for Biston segregate as mendelian variants has become grist for the creationists’ mill. males it merely buys a ticket in the copulatory when tested under uniform experimental By peddling innuendo and failing to lottery of possible fatherhood”, she argues. conditions. Perhaps Hooper embraces the distinguish clearly the undeniable fact What differs, she continues, is not the induction theory because it makes for a bet- of selection from the contested agent of rewards, but the costs (the risk of injury). ter story, but surely good science journalism selection, Hooper has done the scientific This argument explains why women are less demands that drama takes a back seat to data. community a disservice. I prone to seek high status through aggressive Numerous scientific errors (the American Jerry A. Coyne is in the Department of Ecology competition. It is also used to good effect in a peppered moth is not B. cognataria but and Evolution, University of Chicago, 1101 East later chapter on women and crime, in which B. betularia, the same species as in Britain, 57th Street, Chicago, Illinois 60637, USA. Campbell explains why women commit