SOS Bushmen

Locations for the Garden of Eden have been offered many times before, but seldom in the somewhat inhospitable borderland where Angola and Namibia meet. A new genetic survey of people in Africa, the largest of its kind, suggests, however, that the region in southwest Africa seems, on the present evidence, to be the origin of modern humans. The authors have also identified some 14 ancestral populations.

The new data goes far toward equalizing the genetic picture of the world, given that most genetic information has come from European and Asian populations. But because it comes from Africa, the continent on which the human lineage evolved, it also sheds light on the origins of human life.

"I think this is an enormously impressive piece of work," said Alison Brooks, a specialist on African anthropology at George Washington University.

The origin of a species is generally taken to be the place where its individuals show the greatest genetic diversity. For humans, when the new African data is combined with DNA information from the rest of the world, this spot lies on the coast of southwest Africa near the Kalahari Desert, the research team, led by Sarah Tishkoff of the University of Pennsylvania, said in last week's issue of Science.

Brooks said that it had some trees but that it also had deep sand and was not garden-like. The area is a homeland of the Bushmen or San people, whose language is distinguished by its many click sounds.

Language clues

But the San in the past might not have been restricted to where they are now, she said. The San are thought to have once occupied a much larger area, one that probably stretched from southern Africa up the east coast to as far as present-day Ethiopia.

Because the geneticists' calculations refer to people, not geography, the San - and therefore the site of greatest human diversity - might have been located elsewhere in the past.

Christopher Ehret, an expert on African languages at the University of California, Los Angeles, and a member of Tishkoff's team, has detected traces of words borrowed from click languages in East African languages. This suggests that proto-Khoisan, the inferred ancestral language of all click-speakers, may have originated in East Africa, Brooks said.

The language of the first modern humans may have undergone a very early branching, Ehret said, with the Khoisan click languages on one branch and the other three language groups of Africa - Nilo- Saharan, Niger-Kordofanian and Afroasiatic - on the other branch. Another finding of the Tishkoff-Ehret team is that African languages tend to be correlated with the genetics of their speakers, a finding that helps indicate cases of language replacement. The various Pygmy groups in Africa, the team has found, show genetic relationships to the San and other click-speakers, suggesting the pygmies, too, once spoke Khoisan languages but have now adopted those of their neighbors.