African ancestors evolved protection from UV radiation
Prehistoric Africans evolved increased protection from sunlight.
The discovery is one of several to emerge from the first in-depth study of ancient human DNA from sub-Saharan Africa.
An international research team led by Harvard Medical School in the US tested DNA from 15 ancient residents of the region - including three from the Western Cape - ranging in age from 500 to 8,500 years.
The team, which included geneticists and archaeologists from the universities of Cape Town and Pretoria, said their findings gave the first glimpses of population distribution before farmers and animal herders swept across the continent about 3,000 years ago.
They also identified a population that spanned an area from the southern tip of Africa to the equator about 1,400 years ago, and said the group shared ancestry with today's Khoi-San.
Delving into the deep ancestry of African groups has been impossible until recently because genetic material degrades too rapidly in warm, humid climates. But the team found DNA lasts longer in small, dense ear bones, and used those in their tests.
Researchers identified two regions of the genome that appeared to have undergone natural selection in Southern Africans.
One increased protection from ultraviolet radiation, which the researchers think could be related to life in the Kalahari desert. The other was on genes related to taste buds, which could help people to detect poisons in plants.