Genetic studies reveal that an African woman from less than

200,000 years ago was our common ancestor

By Rebecca L. Cann and Allan C. Wilson

POINT-COUNTERPOINT: For an opposing view of how humankind arose around the globe, see "The Multiregional Evolution of Humans," on page 46.

In the quest for the facts about human evolution, we molecular geneticists have engaged in two major debates with the paleontologists. Arguing from their fossils, most paleontologists had claimed the evolutionary split between humans and the great apes occurred as long as 25 million years ago. We maintained human and ape genes were too similar for the schism to be more than a few million years old. After 15 years of disagreement, we won that argument when the paleontologists admitted we had been right and they had been wrong.

Once again we are engaged in a debate, this time over the latest phase of human evolution. The paleontologists say modern humans evolved from their archaic forebears around the world over the past million years. Conversely, our genetic comparisons convince us that all humans today can be traced along maternal lines of descent to a woman who lived about 200,000 years ago, probably in Africa. Modern humans arose in one place and spread elsewhere.

Neither the genetic information of living subjects nor the fossilized remains of dead ones can explain in isolation how, when and where populations originated. But the former evidence has a crucial advantage in determining the structure of family trees: living genes must have

AFRICAN ORIGIN for all modern humans is indicated by the genetic evidence. A genealogy based on 182 current mitochondrial DNA types (outeredges) points to the existence of a common female ancestor from Africa. The arrows on the map (center) indicate the route and the minimum number of unrelated females (red circles) who colonized various areas, as inferred from the branching pattern.

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