15 January 2007
New signposts on the path of early human migration
An old South African skull and an ancient settlement along the Don River in Russia lend crucial support to the idea that modern humans spread from Africa across Eurasia only 50,000 years ago. The only evidence of modern humans outside of Africa is a couple of sites about 100,000 years old in Israel which appear to have been abandoned as the Ice Age grew more severe.
Genetic studies suggest that modern humans did not emerge from Africa until about 50,000 years ago, but that late date has been controversial. Now, two new studies support the genetic evidence, says Ted Goebel at the Center for the Study of the First Americans at Texas A&M University, USA. Originally found in a dry riverbed in 1952, the South African skull was unsuitable for radiocarbon dating. Using new technology, Richard Bailey and other researchers at the University of Oxford measured the amount of radiation that had been absorbed by sand grains that had filled the braincase since its burial. So, they dated the sediment encased inside the skull to 36,000 years ago (plus or minus 3,000 years), and says the skull resembles the first modern humans who lived in Europe at about the same time. Citing that resemblance, the team led by Frederick Grine of Stony Brook University in New York concludes that the South African fossil and its European contemporaries shared a recent common ancestor, and that modern humans had therefore arrived in Europe not long before.
The Paleolithic site in Russia is between 42,000 and 45,000 years old, predating early human finds in central and eastern Europe. The only human fossils are teeth that cannot be identified by species, but the artifacts – including possible art and shells imported from more than 500 kilometres away – look like they were made by early modern humans, argue Mikhail Anikovich of the Institute of the History of Material Culture in St. Petersburg, Russia, and colleagues. The location suggests that modern humans may have arrived from further east in Eurasia than in the classic depiction, in which Cro-Magnon man passed through Turkey into Europe, says Goebel.
The excavation took place at Kostenki, a group of more than 20 sites along the Don River that have been under study for many decades. Kostenki previously has yielded anatomically modern human bones and artifacts dating between 30,000 and 40,000 years old, including the oldest firmly dated bone and ivory needles with eyelets that indicate the early inhabitants were tailoring animal furs to help them survive the harsh climate.
The site also has yielded perforated shell ornaments and a carved piece of mammoth ivory that appears to be the head of a small human figurine, which may represent the earliest piece of figurative art in the world, he said. "The big surprise here is the very early presence of modern humans in one of the coldest, driest places in Europe," John Hoffecker, a fellow of CU-Boulder's Institute of Arctic and Alpine Research, said. "It is one of the last places we would have expected people from Africa to occupy first." Kostenki also contains evidence that modern humans were rapidly broadening their diet to include small mammals and freshwater aquatic foods, an indication they were "remaking themselves technologically," he said.
Much more remains to be learned about modern human migration, but Goebel says the crucial sites will probably be in "places like Iran or Afghanistan, where European and US archaeologists haven't been able to work for decades."
Sources: EurekAlert!, New Scientist (11 January 2007), BBC News, The New York Times (12 January 2007)