If Climate Didn't Doom Neanderthals, Did Humans?
By Brandon Keim, Wired Blog Network, December 29, 2008
Neanderthals could handle the weather, but they couldn't handle us. That's the conclusion of a new study published Monday.
Soon after modern humans arrived in Western Europe, plenty of temperate, food-rich habitat existed for our evolutionary near-brothers — but their settlements dwindled, and modern human settlements spread.
These patterns suggest that one of modern anthropological history's great mysteries had a harsh ending: a competition in which Neanderthals, for reasons still unknown, were doomed.
"Neanderthals didn't end up being the champion lineage that emerged from the end of the Pleistocene," said A. Townsend Peterson, a Kansas University evolutionary biologist and co-author of a new study. "Wouldn't it be fascinating to understand that weird point in human history, when there were two lineages of Homo, in the same region?"
One popular explanation holds that climate changes were inhospitable to Neanderthals unable to keep pace with fluctuations in food and weather.
Indeed, the overlapping twilight of the Neanderthals and dawn of modern humans in Western Europe, roughly spanning the period 45,000 to 35,000 years ago, was a time of intense climate disruption. Massive icebergs melting in the North Atlantic stalled major oceanic currents, producing rapid regional oscillations between balmy mildness and harsh cold.
Even so, when Peterson's team plugged existing data on late-Pleistocene weather patterns and topography into climate simulations that produced a locale-specific model of ecological conditions, they found that suitable habitat still existed for both Neanderthals and modern humans. But archaeological evidence of Neanderthal settlements shows their populations dwindled as their brethren became plentiful.
"You can't wave your hands and say it was climate change," said Peterson, who demurred at describing actual conflict between the groups. "We're not demonstrating that there was some sort of interaction. We're simply demonstrating that the alternative explanation doesn't cut it," he said.
But the team's paper, "Neanderthal Extinction by Competitive Exclusion," suggests competition, a hypothesis strengthened by the eventual diffusion of modern humans into the Neanderthals' last stronghold in what is now Spain. Neanderthals soon disappeared there as well.
Study co-author William E. Banks, a University of Bordeaux archaeologist, made no bones about it. "Our modeling indicates that Neanderthals could have exploited a niche expressed across most of Europe," he said. "The fact that their final contraction to southern Spain coincides with the geographic expansion of the anatomically modern human niche is not coincidence."
University of Utah anthropologist Henry Harpending, who reviewed the paper for its publication Monday in Public Library of Science ONE, called the findings "a real solid blow against the climate hypothesis," and lauded the researchers' careful analysis.
"There's a flood of papers out there about how selenium deficiency or cannibalism or one thing or another led to the Neanderthal extinction, and most are nonsense," he said. "This was real solid science."
But Harpending cautioned that other explanations, such as disease, are plausible, though no evidence for them exists, and perhaps never will.
"There's no way of knowing," he said.
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