Early humans may have evolved black skin to protect against a very high risk of dying from ultraviolet light (UV)-induced skin cancer, a new analysis concludes.
Skin cancer has usually been rejected as the most likely selective pressure for the development of black skin because of a belief that it is only rarely fatal at ages young enough to affect reproduction.
But a new paper, published in Proceedings of the Royal Society B, cites evidence that black people with albinism from parts of Africa with the highest UV radiation exposure, and where humans first evolved, almost all die of skin cancer at a young age.
The paper, by Professor Mel Greaves at The Institute of Cancer Research, London, cites studies showing that 80 per cent or more of people with albinism from African equatorial countries such as Tanzania and Nigeria develop lethal skin cancers before the age of 30.
Albinism is also linked to skin cancer in indigenous populations of other tropical countries with high, year-round UV exposure such as Panama.
Professor Greaves argues that the fact that people with albinism, which is caused by genetic changes that prevent the production of melanin, develop cancer at reproductive ages is indirect but persuasive evidence that early, pale-skinned humans were under strong evolutionary pressure to develop melanin-rich skin in order to avoid lethal skin cancer.
Genetic evidence suggests that the evolution of skin rich in eumelanin, which is brown-black in colour, occurred in early humans between 1.2 and 1.8 million years ago in the East African Savannah. Early humans having lost most of their body hair (probably to facilitate heat loss) probably had pale skin containing pheomelanin - like our nearest surviving relatives, chimpanzees. Pheomelanin, characteristic of white skin, is red-yellow and packaged into smaller stores under the skin than eumelanin, characteristic of black skin. Eumelanin provides a much
|Contact: Henry French|
Institute of Cancer Research