WASHINGTON — Africans are more diverse genetically than the inhabitants of the rest of the world combined, according to a sweeping study that carried researchers into remote valleys and mountaintops to sample the bloodlines of more than 100 distinct populations.
The report, published Thursday in 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, 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 human beings originated in Africa about 200,000 years ago, and all human beings today are their direct descendants. The study points to an area along the Namibian-South African border, the homeland of the San people, as the starting point for a southwest-to-northeast migratory route through Africa and exiting the continent at about the midpoint of the Red Sea.
By offering a richer database than had previously been available for African genetic diversity, the new findings will help doctors and medical researchers tailor drug treatments for different groups of Africans rather than treating them as a homogenous population.
“I think 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.”
“There’s been so much genetic analysis that’s been so Eurocentric,” she said.
The research makes all the more vivid the differences among the continent’s many ethnic groups, which include the Hadzu, the San, the Dinka, the Mbuti, the Nuer, the Fulani, the Beja, the Tuareg, and hundreds of other populations. The Tishkoff team looked at a total of 121 African population groups from about 2,000 such groups on the continent.
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