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.