12 January 2007

Human Diaspora May Have Occurred Later Than Previously Thought

by Kate Melville

Modern humans spread out of Africa up to 50,000 years later than previously thought, say anthropologists. Three new studies in the current issue of Science examine precisely when it was that modern humans evolved in Africa, left Africa and colonized different areas of the Old World.

Until now, theories held that modern humans spread from Africa 100,000 years ago. New data, however, suggest that their migration occurred only 50,000 to 60,000 years ago, explains anthropologist Ted Goebel, at Texas A&M. Additionally, he believes the spread of modern humans in eastern Europe and Russia occurred earlier than previously thought.

The new information, says Goebel, is based on paleontological evidence of human fossils including a modern human skull from Hofmeyer, South Africa, that was discovered in 1952, mitochondrial DNA used to research modern human dispersal from western Asia and archeological evidence from artifacts found at the Kostenki sites along the Don River in Russia.

Dating techniques revealed that the sediment in the Hofmeyer skull was deposited 36,000 years ago. According to the study, the Hofmeyer skull is more similar to modern humans of Upper Paleolithic Europe than recent South Africans or Europeans and has little in common with Neanderthals.

"The idea is that modern humans developed around 100,000 years ago or so in east Africa," says Goebel. "When they developed the physical and behavioral repertoire that we consider to be modern, they then successfully colonized new areas. This new evidence suggests that modern humans spread out of Africa very late in the Pleistocene era."

The DNA analyzed in another study suggests that two genetic lineages originated simultaneously in western Asia between 40,000 and 45,000 years ago and from there spread into northern Africa. And artifacts found at the Kostenki sites led researchers to believe that part of central Eurasia and Russia were colonized just as early as Europe by modern humans.

"What we have are three pieces of the puzzle and they help us test the new theory and all pretty much support this notion that modern humans evolved in Africa and then they spread from Africa," said Goebel.

Source: Texas A&M University