A University of Tennessee anthropologist has found new evidence that Neanderthals and emerging modern humans were not distinct species, but evolved together and probably interbred.
Dr. Andrew Kramer performed a comparative analysis of fossil skulls from the late Pleistocene Levant, the eastern Mediterranean area where Neanderthals and early modern humans probably first encountered one another.
Neanderthals appeared in Europe about 250,000 years before the present time, then disappeared 25,000 to 30,000 years ago. Paleoanthropologists have disagreed for a century about what happened to them.
The Out of Africa theory affirms that Neanderthals were one of multiple species replaced by modern humans migrating from Africa around 200,000 years ago.
The opposing theory, multiregionalism, proposes that there have been distinct populations of humans living around the world since a migration one to two million years ago -- and that modern humans are a result of the constant intermingling of these groups over time.
Kramer analyzed skulls found in the Levant and dated to 60,000 years before Neanderthals disappeared from Europe. His sample included both crania identified as Neanderthal and as modern human. Because the two groups apparently lived side-by-side during this period, a comparison of their cranial features presents a unique opportunity to test the Out of Africa theory.
Working with Drs. Milford Wolpoff (University of Michigan) and Tracy Crummett (San Jose State University), Kramer selected 12 cranial features present on most or all of the Levantine skulls.
Before applying the analysis, the researchers tested the features by using them to compare Neanderthal and early modern human crania from Europe. The same data that sorted these last samples into two distinct groups showed no distinctive differences among the skulls from the Levant.
The results, published in the January 2001 issue of Quaternary International, suggest that the two populations intermingled in the Levant as a result of one of many waves of migration out of and into Africa -- and that Neanderthals and early modern humans were members of one species.
"Demonstrating that there is no defining difference between the skulls from the Levant hardly lays the Out of Africa issue to rest," says Kramer, "but it does give strong support to a model of multiregional evolution where humans with modern characteristics appeared first in Africa -- and, as they spread and expanded their range -- mixed with the other human populations they encountered rather than replacing them."
[Contact: Dr. Andrew Kramer]