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.

Kettlewell was the only son of Kate Davis and of Henry Kettlewell, a merchant and member of the Corn Exchange. He was educated at Old College, Windermere, and then at the renowned English public school Charterhouse (1920–1924); studied briefly in Paris; read medicine (with zoology) at Gonville and Caius College, Cambridge, from 1926; and undertook his clinical training at St. Bartholomew’s Hospital, London, form 1929. In 1935, after graduating in medicine, he joined a general medical practice in Cranleigh, Surrey. The following year he married Hazel Margaret Wiltshire. They had a daughter who died young and a son.

During World War II Kettlewell worked for the Emergency Medical Service at the Working War Hospital. He was also for a time an anesthetist at a hospital in Guildford. With the inauguration of the National Health Service, Kettlewell left general medical practice, and in 1949 he moved to South Africa to carry out research at the International Locust Control Centre at Cape Town University, making several expeditions to the Kalahari, the Knysna Forest, the Belgian Congo, and Mozambique. In 1951 he was appointed to a senior research fellowship in the laboratory of Edmund Brisco Ford in the zoology department at Oxford, dividing his time between England and South Africa until 1954, when he was appointed senior research officer and finally settled in Oxford.

It was there that he carried out his best-known work, on the evolution of melanism in moths, over a period of two decades, leading his small research team, which sometimes included his wife and son, with great panache. Although he had the true comedian’s deep streak of sadness. Bernard Kettlewell was a big man, with a personality larger than life. Kind, charming, and irascible, he had a huge and infectious ebullience and energy, could be the life and soul of any party, and was much loved by his friends. In 1952 he returned to England by driving from Cape Town to Alexandria, surely with the same abandon with which he used to drive the English lanes. He retired in 1974 and died five years later, from an apparently accidental overdose of the medication he was using to relieve the pain of a back injury sustained during fieldwork.

Kettlewell belonged to that English tradition which sees no sharp boundary between amateur naturalist and professional biologist. As perhaps the last great exponent of that tradition, it was appropriate that he saw his work as confirming the work of its greatest exponent of all time, Charles Darwin, and that his first profession, medicine, was also Darwin’s. From his youth Kettlewell had shown an extraordinary facility for fieldwork with insects, in his teens finding species which had completely eluded experienced collectors, and later in life establishing in three days the life cycle of a rare species which had defeated a large team of enthusiasts. It was this ability which he exploited so superbly in the work he carried out at Oxford, where, at some financial loss, he converted his lifelong hobby of entomology into a profession. Theingenuity with which he could combine science and natural history was shown by his demonstration that a moth caught in his trap had migrated direct from North Africa—it was carrying a radioactive particle from a French nuclear test explosion.

Because of a long friendship with Edmund Ford, whom he had met in the Black Wood of Rannoch, a famous ecological site, in 1937, Kettlewell had agreed to join the team Ford was building up in Oxford for the “study of evolution by observation and experiment” to investigate the most spectacular and rapid evolutionary change ever witnessed; industrial melanism in moths. It was the ideal experimental situation, in which all variables but one have been manipulated into insignificance. Thenormal richness and complexity of the coadaptations of organisms with each other and with their physical environment had been almost obliterated by one overwhelming factor: the industrial and domestic soot which blanketed the more populous parts of Britain and Europe.

The extermination of the lichens that otherwise clothed the trunks of trees had left those moths which spent the day exposed there, relying only on stillness and invisibility, deprived of the camouflage they had enjoyed. Forced to rest on the soot-blackened bark, some eighty species of them had darkened during the nineteenth century. This was well enough known, and had been subjected to various neo-Lamarckian, mutationist, and (notably by J. B. S. Haldane) Darwinian interpretations, but it was Kettlewell who used it to provide spectacular evidence of the competence of natural selection to produce evolutionary change.

The two personal qualities that led to this success were Kettlewell’s great facility with insects in the field, and his status as an amateur entomologist. Although walking with the kings of population genetics, he had not lost the common touch; his knowledge of natural history and his enthusiasm for the natural history and his enthusiasm by the amateur lepidopterist, who found the work of the more rigorously trained of Kettlewell put this power to communicate with the amateur world to good effect in organizing a national survey (1952– 1970), conducted by 170 entomologists, of the distribution of the black and the lichen-patterned forms of one of the more prominent industrial melanics, the peppered moth (Biston betularia). This showed clearly that the highest frequencies of the black forms were found in the heavily polluted industrial heartlands of Britain, and that populations in the western and northern rural areas were still entirely of the lichen-camouflaged form.

By using a massive field experiment, replicated in polluted and unpolluted woodlands in 1953 and 1955, and with the help of Niko Tinbergen in observing and filming the insectivorous birds which attacked the moths during the day, Kettlewell showed that twice as many of the black form as of the pale form survived in polluted woodland, the situation being reversed in the unpolluted wood. This constituted what he described as-Darwin “missing evidence,” that evolutionary changes could be produced in natural populations through the force of natural selection acting on inheritable variation. It was a problem that could have been solved only in this way, by direct work in the field by a field naturalist. Kettlewell’s demonstration was of such elegance and simplicity as to make it one of the great classics of evolutionary biology.

During his amateur and his professional work, Kettlewell built up a large collection of Lepidoptera, rich in specimens demonstrating the genetics of melanism and other variations, which he combined with the collection of A. E. Cockayne, another medical amateur entomologist with a distinguished reputation in genetics. United with Lord Rothschild’s collection, this became the Rothschild-Cockayne-Kettlewell collection of the British Museum, a unique resource for the study of natural variation and its inheritance.

The fame his research brought him led to more popular scientific commissions: an expedition to Brazil in 1958 to commemorate the centennial of Darwin’s Origin of Species. which Kettlewell converted into a study (with a film) of insect camouflage, and a biography of Darwin (jointly with Julian Huxley), which was a pioneering example of the now standard genre of scientific biographies decorated with contemporary illustrations.

In the work that immediately followed his classic experiments, Kettlewell extended his interest to species which were melanic, and had perhaps been so for a long time, in rural rather than industrial environments: his most notable study was of Amathes (Paradiarsia) glareosa, which becomes darkened in the Shetland Isles as a result of flying in subarctic twilight against black, peaty soil. Melanism, according to his book The Evolution of Melanism, was therefore a’ recurring necessity, ’ arising in many and varied circumstances when moths were predated on a darkened background. industrial pollution providing but the latest of these. This view opened a way of comparing the coadaptation of the whole genome to genes which had been present for a long period with those that were newly arisen. This synthesis attracted relatively little attention, in part because it entailed Ronald A. Fisher’s theory of the evolution of dominance, always dear to members of Ford’s school of ecological genetics but deeply controversial among geneticists.

Although some of Kettlewell’s students extended his work to additional species, research on melanism showed signs of withering within five years of his death. Three of its best practitioners (Philip M. Sheppard, E. Robert Creed, James A. Bishop) had died young; Kettlewell’s personal style, on which the research greatly depended, was inimitable; and funding from the scientific establishment was sparse. The Royal Society declined to elect him to a fellowship, and it was significant that Kettlewell’s formal honors were all awarded in the Soviet bloc (Darwin Medal, Soviet Union, 1959; Mendel Medal, Czechoslovakia, 1965) and that in Darwin’s own country, Kettlewell had found the’ missing evidence’ not with state funds but with a grant from the privately administered Nuffield Foundation.

BIBLIOGRAPHY

1.Original Works. Kettlewell’s major book is The Evolution of Melanism: The Study of a Recurring Necessity (Oxford, 1973). The bibiography contains an extensive, but not exhaustive, compilation of his scientific papers; the preface and acknowledgments contain some autobiographical material. Kettlewell’s two more popular works are Your Book of Butterflies and Moths, which communicates clearly his enthusiasm for natural history (London, 1963), and Charles Darwin and His World (London and New York, 1965), with Julian Huxley. The chief papers describing his experiments on Biston betularia were published in Heredity: “Selection Experiments on Industrial Melanism in the Lepidoptera,” 9 (1955), 323– 342; “Further Selection Experiments on Industrial Melanism in the Lepidoptera,” 10 (1956), 287–301; and “A Survey of the Frequencies of Biston betularia L. (Lep.) and Its Melanic Forms in Britain,” 12 (1958), 51–72. For a wider audience he wrote“arwin”s Missing Evidence, ’ in Scientific American, 200 (March 1959), 48–53. His two films, later to look amateur beside the work of professional wildlife moviemakers, but pioneering classics in their day, were Evolution in Progress (cinematographer Niko Tinbergen, 1956) and Darwin and the Insects of Brazil (with the Shell Film Unit, 1958) (both distributed by British Universities Film and Video Council, London). The annotated Rothschid-Cockayne-Kettewell National Collection of British Lepidoptera is in the British Museum (Natural History), London.

II. Secondary Literature. Obituaries are Cyril A. Clarke, in Antenna, 3 no. 4 (1979), 125, and Entomologist’s Record and Journal of Variation, 91 no. 10 (1979), 253– 255; R. F. Demuth, ibid., 255–257; E. B. Ford, in Nature, 281 (1979), p. 166; and E. P. W. [Wiltshire], in Proceedings of the British Entomological and Natural History Society, 12 no. 3/4 (1979), 101–103. For a scientific review of Kettlewell’s work in context, see Edmund B. Ford, Ecological Genetics (London, 1964; 5th ed., 1975), ch. 14. A copy of the Granada TV film about about his Shetland work is held by the biology department of the University of York.

John R. G. Turner