for National Geographic News
A massive new study of human genetic diversity reveals surprising insights into our species' evolution and migrations—including support for the theory that the first modern humans originated in Africa—scientists said today.
Researchers compared 650,000 genetic markers in nearly a thousand individuals from 51 populations around the globe—an unprecedented level of detail for a human genetic study.
"You get less and less variation the further you go from Africa," said Marcus Feldman, an evolutionary biologist at Stanford University in California and a study co-author.
Such a pattern fits the theory that the first modern humans settled the world in stepping-stone fashion after leaving Africa less than 100,000 years ago.
As each small group of people broke away to found a new region, it took only a sample of the parent population's genetic diversity.
"If you keep sampling like that, then mathematically you must lose variation," Feldman explained.
The research appears in tomorrow's issue of the journal Science.
Sharpest Detail Yet
The new study, as well as related research published yesterday in the journal Nature, offer the sharpest pictures to date for understanding variation in the human genome.
(Read "Europeans Less Genetically Diverse Than Africans" [February 20, 2008].)
Previous studies have looked only at a thousand or so genetic markers and compared them between three or four populations. The new studies examine hundreds of thousands of markers in dozens of populations.
"It's sort of like looking at Mars with the naked eye versus with a big, very powerful telescope," said Richard Myers, a geneticist and study co-author also from Stanford University.
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