Kettlewell, Henry Bernard David (1907-1979)

Industrial melanism in the peppered moth, first noticed by English geneticist Henry Kettlewell. He observed that whereas in rural areas peppered moths were light in colour to camouflage them against the lichens, in industrial areas where the tree trunks were dirtied with soot, peppered moths were darker. Natural selection favoured the darker mutation in industrial areas because it offered better camouflage there, so it had become widespread, whereas in rural areas the darker mutant was highly visible against the lighter tree trunks and so was easy prey to insect feeders.

English geneticist and lepidopterist who carried out important research into the influence of industrial melanism on natural selection in moths, showing why moths are darker in polluted areas.

Kettlewell was born in Howden, Yorkshire, and studied medicine at Cambridge and at St Bartholomew's Hospital, London. He was based at Cape Town University, South Africa, 1949-52, investigating methods of locust control and going on expeditions. Returning to the UK, he spent the rest of his career at Oxford as a genetics researcher.

Kettlewell's research into industrial melanism focused on the peppered moth Biston betularia. 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.