New evidence ages modern Europeans.

New Evidence Ages Modern Europeans

Seven bits of charcoal, excavated from two caves in northern Spain and analyzed with a recently developed variation of radiocarbon dating, may herald a major shift in the debate over the origins of anatomically modern humans in Europe. A new study suggests that stone tools and other remains of the Aurignacian culture, generally attributed to the handiwork of the earlist European Homo sapiens sapiens, date to nearly 40,000 years ago in western Europe -- about 6,000 years earlier than previously thought.

The results challenge the widespread assumption that a gap of several thousand years existed between the end of western Europe's Mousterian culture, characterized by simple stone tools linked to the Neanderthals, and the Aurignacian entrance into the same region, says James L. Bischoff of the U.S. Geological Survey in Menlo Park, Calif. Bischoff and four Spanish colleagues report their findings in the December JOURNAL OF ARCHAEOLOGICAL SCIENCE.

Aurignacian technology apparently spread westward from eastern Europe, where it dates to about 43,000 years ago, much faster than usually thought, the researchers contend. Thus, modern humans may have abruptly replaced Neanderthals in southwestern Europe.

Disputes over the evolutionary relationship of Neanderthals to modern humans remain far from settled (SN: 2/27/88, p.138), but the new evidence "opens the debate to a wide variety of possibilities," says Lawrence G. Straus of the University of New Mexico in Albuquerque. For example, he writes in the Nov. 30 NATURE, if Aurignacian skills developed at roughly the same time throughout Europe, Neanderthals may have evolved directly into anatomically modern Cro-Magnons with little or no interbreeding with Asian and African populations of H. sapiens sapiens.

This contrasts with the currently popular view that Neanderthals were a dead-end branch of humanity replaced by modern humans, who originated in Africa and spread throughout the world.

"If the Spanish dates are accurate, they represent something revolutionary," says Randall White of New York University in New York City. What emerges is a "more mosaic, complicated picture" of the European transition from Neanderthals to modern humans, he notes.

But White says he will remain skeptical of Bischoff's findings until the same dating technique -- known as accelerator mass spectroscopy (AMS) radiocarbon dating -- is applied to other Aurignacian sites. Other researchers who recently used the AMS technique to study an early human site in France placed it at only about 34,000 years old, he points out.

AMS radiocarbon dating was developed about eight years ago, and its archaeological use began several years ago. It is considerably faster than the conventional method and handles much smaller samples, says physicist Douglas J. Donahue of the University of Arizona in Tucson, where Bischoff's charcoal was dated. The dating range of both methods is about 50,000 years, he adds.

Conventional radiocarbon dating measures the decay of carbon-14 atoms in chunks of organic material and calculates age from the ratio of carbon-14 to stable carbon atoms. For AMS dating, thumb-nail-sized samples are placed in a high-energy mass spectrometer, where carbon atoms of different mass are separated and counted.

AMS allows investigators to confirm dating estimates on several samples from the same sediment layer, a luxury usually unavailable with the conventional technique because of the large amounts of material required for dating.

Bischoff's team obtained three AMS dates for the earliest Aurignacian layer at one Spanish cave and four dates at the second cave, all of which date to nearly 40,000 years ago. Charcoal from the second cave indicates the Mousterian culture ended about 40,400 years ago.

The new evidence suggests Neanderthals may have borrowed tool-making styles from modern humans in southwestern Europe and developed the distinct implements of the Chatelperronian culture, which disappeared around 33,000 years ago, Bischoff says. But whether Neanderthals and modern humans interbred remains an open question, he asserts.