Unearthing The Roots of The Human Family Tree

April 28, 2008 02:13 PM
by findingDulcinea Staff
New research suggests that two early human populations lived in isolation of one another for up to 100,000 years, perhaps nearly evolving into two species.

30-Second Summary

The study, published in the American Journal of Human Genetics, shows that shortly after Homo sapiens emerged about 200,000 years ago a drought caused the species to separate into two distinct populations located in eastern and southern Africa.

The split occurred about 150,000 years ago and lasted between 50,000 and 100,000 years. If the study is correct, this “would be the longest period for which modern human populations have been isolated from one another,” reports the BBC.

Because humanity started in Africa, the continent’s genetic diversity “probably exceeds that of the rest of the world put together,” according to The Economist. But just how that diversity evolved is unclear. That’s why the report analyzed the mitochondrial DNA of 600 living Africans.

Mitochondrial DNA passes from mother to child, making mutations easy to trace. As a result, the study shows that the Khoi San hunter-gatherer populations of southern Africa share the mitochondrial lineage of one of the two communities, while the populations in east and west Africa, and the rest of the world, share the lineage of the other community.

The results, which come from the Genographic Project, also reinforce the findings of a Stanford University study showing that the same drought that split Homo sapiens may have also brought it close to extinction. At one point, the human population may have fallen to as low as 2,000 people.

But some scientists, such as Dr. Sarah Tishkoff of the University of Pennsylvania, say it is still to early to paint an accurate picture of humanity’s early history in Africa.

Headline Links: Study uncovers genetic split in ancient humans

Background: Humans nearly Extinct

Related Topics: Oldest human fossils found and tracing human evolution in America

Reference: The Genographic Project and mitochondrial DNA


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