When Did the First People Go Out of Africa?

Scientists agree than modern human species appeared about 100,000 years ago in Africa, from where they colonized the whole Earth.

What still puzzles the scientists is the time when ancient people went out of Africa: geneticists and paleoanthropologists have different opinions, going from as early as 100,000 years ago to as recently as 50,000 years ago. Genetic studies have supported a late exodus, while fossil evidence points to an earlier one.

The problem is complicated by the fact that fossils from the crucial period from sub-Saharan Africa are almost missing now. Presently, data offered by an old skull discovered in 1952 offer fresh clues.

An international team led by paleoanthropologist Frederick Grine, of Stony Brook University in New York reanalyzed this ancient skull, found in a dry river bed near Hofmeyr, South Africa. Initial attempts to date it failed and archaeologists believed it was less than 10,000 years old. The team employed optically stimulated luminescence and uranium series to detect the skull's age to about 36,000 years.

The cementlike carbonate soil - deposited shortly after the fossil was buried, and which coated the inside of the skull vault - was dated through radiocarbon. Comparisons revealed that this skull looks more like fossils of Homo sapiens who lived in Europe and Asia about 36,000 years ago than like the fossils of Africans or Europeans from the past 10,000 years.

Thus, the Hofmeyr skull belongs rather to the strain of modern humans who first swept into Europe and Asia, and all these populations originated in a sole population in sub-Saharan Africa; but the skull also enhances the genetic evidence for an about 50,000 years of the first exodus. "If there was a very late migration out of Africa, you would expect Europeans at that time to look like Africans at that time," says Grine.

"I do not see how the skull could possibly be older than the age of the carbonate," says Ann Wintle, an expert in luminescence dating methods at the University of Wales in Aberystwyth, U.K.

This skull is going to be compared with a skull from the same period, which was found in Romania, to see if they are long-lost cousins.

Photo credit: Frederick Grine