Bernard Kettlewell

Henry Bernard Davis Kettlewell (24 February 1907 - 1979) was a British geneticist, lepidopterist and medical doctor, who carried out important research into the influence of industrial melanism on natural selection in moths, showing why moths are darker in polluted areas.

Early life
Kettlewell was born in Howden, Yorkshire, was educated at Charterhouse School, and from 1926 studied medicine with zoology at Gonville and Caius College, Cambridge. In 1929 he began clinical training at St Bartholomew's Hospital, London, then in 1935 joined a general medical practice in Cranleigh, Surrey. He also worked as an anesthetist at St. Luke's Hospital, Guildford. During World War II, from 1939 to 1945, he worked for the Emergency Medical Service at Woking War Hospital.

He emigrated to South Africa in 1949, and from then until 1954 was a researcher at the International Locust Control Centre at Cape Town University, investigating methods of locust control and going on expeditions to the Kalahari, the Knysna Forest, the Belgian Congo and Mozambique.

In 1952 he was appointed to a Nuffield Research Fellowship in the Department of Genetics of the Department of Zoology at Oxford University. Until 1954 he divided his time between South Africa and Oxford, then he gained the position of Senior Research Officer in the Department of Genetics and spent the rest of his career in Oxford as a genetics researcher. His supervisor was E. B. Ford.

Peppered moth investigation and experiments
His grant was to study industrial melanism in general, and in particular the peppered moth Biston betularia which had been studied by William Bateson in the 1890s. Kettlewell's research from three surveys between 1952 and 1972 appeared to show a static pattern with a high frequency of the dark-coloured carbonaria phenotype in industrial regions, and the light coloured typica moths becoming the most common in more rural areas. In the first of Kettlewell's experiments moths were released into an aviary to observe how insectivorous birds reacted. He showed that the birds ate the moths, and found that where the camouflage of the moths made them difficult for him to see against a matching background, the birds too had difficulty in finding the moths. Most famously he then carried out experiments involving releasing then recapturing marked moths in polluted woodlands in Birmingham, and in unpolluted rural woods at Deanend Wood, Dorset, England. He demonstrated experimentally the efficiency of natural selection as an evolutionary force: light-coloured moths are more conspicuous than dark-coloured ones in industrial areas, where the vegetation is darkened by pollution, and are therefore easier prey for birds, but are less conspicuous in unpolluted rural areas, where the vegetation is lighter in colour, and therefore survive predation better. His experiment led to better understanding of industrial melanism and its effects on the evolution of species.

In 1979 Kettlewell died from an accidental drug overdose.