KETTLEWELL, HENRY BERNARD DAVIS

(b. Howden, Yorkshire [now Humberside], England, 24 February 1907; d. Steeple Barton, near Oxford, England, 11 May 1979),

evolution, ecological genetics, entomology. For the original article on Kettlewell see DSB, vol. 17.

In the years since John Turner’s original DSB entry on him, Kettlewell and his pioneering work on industrial melanism have attracted historical interest that extends well beyond its scientific merits. This interest stems from the prominent role his investigations and the phenomenon of industrial melanism have played in the teaching of biology, and the centrality of industrial melanism as an example of natural selection in creationism/intelligent design versus evolution debates. This update summarizes contemporary scientific appraisals of Kettlewell’s classic work on industrial melanism. It then discusses how legitimate scientific questions surrounding Kettlewell and his research have led popular writers and others with a fairly obvious agenda astray. A concluding section summarizes work on Kettlewell by historians and philosophers and outlines outstanding questions for further research.

In textbooks and the popular press, Kettlewell’s field experiments in the 1950s are widely portrayed as providing the first definitive evidence that industrial melanism is indeed an example of natural selection. This is inaccurate for two reasons. First, the evidence that industrial melanism in the peppered moth is an example of natural selection came from the work of geneticists who had established that the color of the peppered moth has a genetic basis (Bowater, 1914), and the observations of literally hundreds of amateur and professional collectors who documented the spread of the dark form in the vicinity of manufacturing areas during the heyday of the industrial revolution and its predictable decline owing to the passage of Clean Air legislation (Doncaster, 1906; Kettlewell, 1958; Cook, 2003; Majerus, 2005). The directional rise and fall of the dark form, not only in the peppered moth but also in literally hundreds of other species where the phenomenon is known to have occurred, definitively establishes that this is an example of natural selection (Majerus, 1998; Grant, 1999). This is true even in the absence of knowing precisely why the dark form is at an advantage in polluted environments. Kettlewell’s field experiments are considered important because they provided the first experimental demonstration that bird predation was indeed the selective mechanism at work at a time when many lepidopterists publicly doubted that bird predation was a significant factor on moth populations (e.g., Allen, 1955).

Second, although they are often depicted in the popular press as definitive, scientists have long recognized several fundamental problems in the conduct of Kettlewell’s initial field experiments (e.g., Clarke & Sheppard, 1966; Majerus, 1998; Grant, 1999). Some of these problems center around the design of his experiment, such as whether the elevated densities of moths he used to ensure his results were statistically significant might have led endemic birds to eat moths when they ordinarily do not. Other problems have been associated with the central assumptions of his investigations, such as where the moth rests by day. While industrial melanism has proven to be a more complicated phenomenon than simplistic textbook accounts would have us believe, at least eight studies since using variously modified experimental designs to get around these problems have confirmed the basic conclusions of Kettlewell’s initial experiments, namely that birds prey upon peppered moths and further that they do so differentially, depending upon how well the moth matches its background (Majerus, 2005). This being said, it seems clear further research needs to be done on the role of other nonvisual components of selection, for example, prelarval survival differences (Cook, 2000, 2003).

Sympathizers with intelligent design have misinterpreted these valid concerns about how best to interpret Kettlewell’s investigations as somehow calling into doubt whether industrial melanism is indeed an example of natural selection at all. Several have drawn attention to discrepancies between introductory textbook accounts on industrial melanism written for children and journal articles by scientists who work on the phenomenon as evidence of a conspiracy to promote evolutionary theory (e.g., Wells, 2000, but see Rudge, 2002).

Following their lead, Judith Hooper, a popular science writer, in the first book-length biography of Kettlewell, all but explicitly charges Kettlewell with committing fraud and suggests Edmund Briscoe Ford and his colleagues engaged in an elaborate coverup to prevent the truth from being widely known (Hooper, 2002). While the book captures a sense of the colorful personalities associated with what has come to be known as the “Oxford School of Ecological Genetics” (c.f. Turner, 1985, 1988, but see Cain, 1988), Hooper’s interpretation of the historical events is fundamentally flawed and rests on shoddy historical research (Rudge, 2005). Scientists familiar with research on industrial melanism have unanimously condemned the book as revealing a woeful misunderstanding of fieldwork in biology (e.g., Coyne, 2002; Grant, 2002). Much of the book is devoted to portraying Kettlewell and his associates as the sort of people who would resort to committing fraud, primarily by drawing attention to the vested interest they had in being able to provide experimental evidence for natural selection in nature.

Her implied allegation that Kettlewell committed fraud centers around a reported increase in recapture rates during his original 1953 investigation, an increase she interprets as evidence Kettlewell “fudged” his data in order to appease his boss Ford. M. Young and I. Musgrave (2005) have shown that the discrepancy upon which Hooper’s specific allegation that Kettlewell fudged his data is made is entirely explicable in the context of field studies. Numerous other interpretive problems in Hooper’s account appear to stem from a lack of field experience (Grant, 2002), poor understanding of the process of natural selection (Majerus, 2005), and a fundamentally flawed understanding of issues associated with the nature of science (Rudge, 2005). It is also unclear that Ford was as intimately involved in Kettlewell’s work as Hooper suggests (Berry, 1990).

Owen (1997) suggests Kettlewell’s published work on industrial melanism inadequately acknowledges his debt to James W. Tutt, who is generally acknowledged as the first to publish the opinion that the reason why the dark form was becoming more common near industrial sites was because of the cryptic advantage of dark coloration in soot-darkened environments (Tutt, 1890). Joel B. Hagen (1999) and David Rudge (1999) have debated whether Kettlewell’s experiment in the unpolluted wood should be interpreted as a control for the earlier experiment in a polluted setting. These papers also raise questions about how this episode has and should be depicted in science textbooks. Rudge (2003) emphasizes the role of visual imagery in accounting for why the example and Kettlewell’s

work on it has become so ubiquitous. Rudge (2000) and Douglas Allchin (2001) have also drawn attention to how this episode can and should be used to teach issues associated with the nature of science.

Several outstanding questions surround Kettlewell’s life and work that will make him the object of continued interest by historians of science. As hinted at in Turner’s original entry, Kettlewell is a fascinating individual in his own right as someone struggling to negotiate between two worlds: the world of the amateur entomologist and the world of the professional scientist. Additional work should be done to clarify the connections between his research on industrial melanism and previous research by amateur and professional scientists in Britain and other countries (briefly mentioned in Kettlewell, 1973, pp. 53–54, and Majerus, 1998). There are also outstanding questions to consider regarding whether and how his research on industrial melanism relates to his other research interests, such as his pioneering use of radioactive isotopes to track insect populations (Rudge, 2005, pp. 257–258). Further historical research on Kettlewell is also of instrumental value in making sense of the complex relationships amongst individuals associated with the Oxford School of Ecological Genetics. (The latter is a particularly important consideration given the relatively complete set of correspondence Kettlewell and Philip Sheppard left behind [archived at the Bodleian Library at Oxford University and the American Philosophical Society Library in Philadelphia respectively] compared to other individuals associated with this group, including Ford and Arthur J. Cain).

SUPPLEMENTARY BIBLIOGRAPHY

WORKS BY KETTLEWELL

“A Survey of the Frequencies of Biston betularia (L.) (Lep.) and Its Melanic Forms in Great Britain.” Heredity 12 (1958): 51–72.

The Evolution of Melanism: The Study of a Recurring Necessity. Oxford: Clarendon Press, 1973.

OTHER SOURCES

Allchin, Douglas. “Kettlewell’s Missing Evidence, a Study in Black and White.” Journal of College Science Teaching 31 (2001): 240–245.

———. “Scientific Myth-Conceptions.” Science Education 87 (2003): 329–351.

Allen, P. M. Review of E. B. Ford’s Moths. Entomologist’s Record and Journal of Variation 67 (1955): 103–104.

Berry, R. J. “Industrial Melanism and Peppered Moths (Biston betularia (L)).” Biological Journal of the Linnean Society 39 (1990): 301–322.

Bowater, W. “Heredity of Melanism in the Lepidoptera.” Journal of Genetics 3 (1914): 299–315.

Cain, Arthur J. “A Criticism of J. R. G. Turner’s Article ‘Fisher’s Evolutionary Faith and the Challenge of Mimicry.’” In Oxford Surveys in Evolutionary Biology, vol. 5, edited by P. H. Harvey and L. Partridge. Oxford: Oxford University Press, 1988.

Clarke, C. A., and P. M. Sheppard. “A Local Survey of the Distribution of Industrial Melanic Forms in the Moth Biston betularia and Estimates of the Selective Values of These in an Industrial Environment.” Proceedings of the Royal Society of London B, Biological Science 165 (1966): 424–439.

Cook, Laurence M. “Changing Views on Melanic Moths.” Biological Journal of the Linnean Society 69 (2000): 431–441.

———. “The Rise and Fall of the Carbonaria Form of the Peppered Moth.” Quarterly Review of Biology 78 (2003): 399–417.

Coyne, J. A. “Evolution under Pressure: A Look at the Controversy about Industrial Melanism in the Peppered Moth.” Nature 418 (2002): 19–20.

Doncaster, L. “Collective Inquiry as to Progressive Melanism in Lepidoptera: Summary of Evidence.” Entomologist’s Record and Journal of Variation 18 (1906): 165–170, 206–208, 222–226, 248–264.

Grant, Bruce S. “Fine Tuning the Peppered Moth Paradigm.” Evolution 5 (1999): 980–984.

———. “Sour Grapes of Wrath.” Science 297 (2002): 940–941.

Hagen, Joel B. “Retelling Experiments: H. B. D. Kettlewell’s Studies of Industrial Melanism in Peppered Moths.” Biology and Philosophy 14 (1999): 39–54.

Hooper, Judith. Of Moths and Men: An Evolutionary Tale. New York: W.W. Norton, 2002.

Majerus, Michael E. N. Melanism: Evolution in Action. Oxford: Oxford University Press, 1998.

———. “The Peppered Moth: Decline of a Darwinian Disciple.” In Insect Evolutionary Ecology: Proceedings of the Royal Society’s 22^nd Symposium, edited by M. D. E. Fellowes, G. J. Holloway, and J. Rolff. Cambridge, MA: CABI Publishing, 2005.

Owen, Denis F. “Natural Selection and Evolution in Moths: Homage to J. W. Tutt.” Oikos 78 (1997): 177–181.

Rudge, David. “Taking the Peppered Moth with a Grain of Salt.” Biology and Philosophy 14 (1999): 9–37.

———. “Does Being Wrong Make Kettlewell Wrong for Science Teaching?” Journal of Biological Education 35, no. 1 (2000): 5–11.

———. “Cryptic Designs on the Peppered Moth.” International Journal of Tropical Biology and Conservation (Revista de Biología Tropical) 50, no. 1 (2002): 1–7.

———. “The Role of Photographs and Films in Kettlewell’s opularizations of the Phenomenon of Industrial Melanism.” Science & Education 12 (2003): 261–287

. ———. “Did Kettlewell Commit Fraud? Re-examining the Evidence.” Public Understanding of Science 14, no. 3 (2005): 249–268.

Turner, J. R. G. “Fisher’s Evolutionary Faith and the Challenge of Mimicry.” In Oxford Surveys in Evolutionary Biology, vol. 2, edited by R. Dawkins and M. Ridley. Oxford: Oxford University Press, 1985.

———. “Reply: Men of Fisher’s?” In Oxford Surveys in Evolutionary Biology, vol. 5, edited by P. H. Harvey and L. Partridge. Oxford: Oxford University Press, 1988.

Tutt, James W. “Melanism and Melanochroism in British Lepidoptera.” Entomologist’s Record and Journal of Variation 1 (1890): 5–7, 49–56, 84–90, 121–125, 169–172, 228–234, 293–300, 317–325.

Wells, Jonathan. Icons of Evolution: Science or Myth? Why Much of What We Teach about Evolution Is Wrong. Washington, DC: Regnery Publishing, 2000.

Young, M., and I. Musgrave. “Moonshine: Why the Peppered Moth Remains an Icon of Evolution.” Skeptical Inquirer 29, no. 2 (2005): 23–28.

David Rudge