Study Genetics in South African

Africans are more genetically diverse than the inhabitants of the rest of the world combined, according to a sweeping study that carried researchers into remote regions to sample the bloodlines of more than 100 distinct populations.

The report, published yesterday in the journal Science Express, suggests that, because of historical migrations and genetic mixing across the continent, it will be hard for African Americans to trace their ancestry in fine detail. African American genealogies are increasingly popular and commercialized, but the authors of the new study cast doubt on how precise such searches can be, given the complexity of the genetic makeup of Africans.

"It may be very challenging to trace back ancestry to particular tribes or ethnic groups, " said Sarah Tishkoff, a University of Pennsylvania geneticist who led the international research team.

The first anatomically modern humans originated in Africa about 200, 000 years ago, and all humans today are their direct descendants. The study points to an area along the Namibia-South Africa border, the homeland of the San people, as the starting point for a southwest-to-northeast migratory route that carried people through Africa and across the Red Sea into Eurasia.

Tishkoff said the new findings will help medical researchers tailor drug treatments for different groups of Africans rather than treating them as homogenous.

"This is an absolute landmark. It's incredible, " said Alison Brooks, a professor of anthropology and international affairs at George Washington University. "It's the most comprehensive document ever published describing the very complex issue of African genetic variation." She added, "There's been so much genetic analysis that's been so Eurocentric."

Tishkoff, who until last year was a professor at the University of Maryland, did much of her fieldwork in remote areas reachable only with four-wheel-drive vehicles. She had to haul centrifuges, for processing blood samples, into villages without electricity, often running her devices by connecting them to her car battery.

"Some people had never seen a fair-skinned person before, " Tishkoff said. "Many of these groups have been studied by linguists and anthropologists, and we've known nothing about their genetic history. Until now."

One of her collaborators, Muntaser Ibrahim of the University of Khartoum, said indigenous people were eager to help the research. "They would like to know about their past as much as everybody else, " he said. "The notion that people in remote areas are not interested in genetics is not true."