DNA Comparison of Africa's Ethnic Groups Quantifies Genetic Diversity: Differences Could Reveal Details of Modern Human Origins
Barazesh, Solmaz, Science News
The largest genetic study of African populations reveals a greater diversity among the continent's cultural groups than previously known, scientists say. The study also offers insight into the origins of modern humans and the ancestry of African-Americans, researchers said in an April 29 teleconference and in a paper posted online April 30 in Science.
Until now, most genetic surveys of this type have used data from just a few African groups assumed to reflect Africa's genetic diversity. But the new research shows that "no single African population is representative of the diversity of the continent," says study coauthor Sarah Tishkoff of the University of Pennsylvania in Philadelphia.
Tishkoff and her colleagues analyzed particular DNA sequences--series of the chemical letters that encode genetic information--from more than 3,000 people from 121 different populations scattered throughout Africa. Researchers divided the participants based on self-identified ethnic groups.
To reach remote groups, such as the Pygmies of Cameroon and the hunter-gatherers of Tanzania, researchers drove off-road and set up makeshift labs with equipment powered by their car battery.
"This is by far the most in-depth analysis in terms of the number of populations analyzed," comments evolutionary geneticist Mark Stoneking of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
The researchers found that the genetic sequences were highly diverse from one population to the next. "We knew that African populations were diverse in culture, art, religious ideas," says Roy King of Stanford University School of Medicine. "Now we see that genetic diversity goes along these same lines."
Because modern humans originated in Africa, there has been more time for changes to accumulate in the African DNA sequences than there has been in sequences from people in other parts of the world, Tishkoff says.
It turns out that the San bushmen of southern Africa have the most distinct, and therefore oldest, genetic sequences, the team reports. …