To the researchers' surprise, however, they uncovered more human remains beneath those of the Neandertals in both caves. These ancient bones dated to an era that stretched from 80,000 to 130,000 years ago. From the deepest layers of dirt beneath the cave floors, which accumulated more than 130,000 years ago, they again found Neandertal bones.
The finding indicated that Skhul and Kafzehand, presumably, much or all of the surrounding regionpassed from human hands back into Neandertal control between 65,000 and 80,000 years ago.
Humans were apparently unsuccessful in their first bid to take over the region.
A Reason for Return
What caused ownership of the caves to flip-flop? Where did the Neandertals retreat to when they first surrendered the region to the newcomers from Africa? And what made the Neandertals reclaim the caves later? Bar-Yosef and Shea set out to answer these questions.
Based on their analysis of the tools and hearths made by the early residents of Israel, the researchers concluded that modern humans didn't use superior technology or intelligence to take over the site. The two groups seem to have been evenly matched in those departments.
Neandertals "were not dumb," Bar-Yosef said. "They weren't making any bone tools or seashell ornaments," like humans were at the time, but "they were digging their hearths exactly like modern humans," he said.
The slight differences in the sophistication of stone tools each group produced could not explain any superiority the humans may have had, the scientists said. And when it came to brute strength, the muscular Neandertals had a clear advantage.
Perhaps Mother Nature had a key role in the power play over the region. Climate changes may have coaxed humans out of Africa and into the region, and encouraged Neandertals already living there to spread outward into other parts of Asia and southeastern Europe.
But a climatic reversal also could have turned the tables. "Neandertal populations [may have been] driven south by rapid climate change around 75,000 years ago," Bar-Yosef said at the meeting in Boston.
Europe and Northern Asia were experiencing a cool era at that time, and even hearty Neandertals probably would have found the warmer climates to the south enticing. They pushed back into the region, probably from the Caucasus region to the north, and drove the humans then living there into retreat, Bar-Yosef suggested.
Only a second advance by humans thousands of years laterone that was more permanently successfulultimately settled the question of which species would prevail.
In a separate presentation at the Boston meeting, archaeologist Mary Stiner of the University of Arizona in Tucson suggested that the later advance by humans might have been set in motion by growing population densities that forced some members of the species to push out of Africa.
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