Climate change has become the default scapegoat for nearly every extinction on Earth lately. But a new study lets climate off the hook for at least one dramatic event: the disappearance of the Neanderthals from Europe about 35,000 years ago.
Scientists have long debated what caused the demise of this human-like species. One camp argues that the Neanderthals fell victim to a dramatic cooling of the environment. The other view holds that prehistoric humans squeezed the Neanderthals out.
"There have been dozens and dozens of articles on one side or the other," said William Banks, an archaeologist at the French Centre National de la Recherche Scientifique in Bordeaux.
Banks led the new study, which suggests that Cro-Magnon populations simply outcompeted Neanderthals during a period of rapid climate change.
The study borrowed a tool from biodiversity research. Called "ecological niche modeling," the technique begins with a look at where a particular species lives. From each region, scientists compile details about geography, climate, and other environmental conditions.
Then, a computer model predicts where else that same suite of conditions exists. The results indicate the species' geographical range and also suggest how that range might expand or contract with environmental changes.
Banks and colleagues applied a version of this technique to ancient human species. They used a database to gather information from about 1,300 archaeological sites around Europe, dating back to three time periods: before, during, and after a massive cooling event about 40,000 years ago.
During that period, called Heinrich Event 4, Europe succumbed to cold, dry weather. Icebergs descended from the Arctic all the way down to Spain. Soon after, nearly all evidence of Neanderthals disappeared from the archaeological record.
Because the Neanderthals petered out around the same time that climate changed, some researchers have concluded that harsh weather was responsible for their demise. However, the species had survived through a number of earlier cold snaps, Banks pointed out, suggesting that cold wasn't what killed them after all.
"It is clear from this paper that the ecology that supported a big population of Neanderthals 40,000 years ago would have supported a big population of Neanderthals 30,000 years ago," said John Hawkes, a paleoanthropologist at the University of Wisconsin in Madison. "This is not an issue of climate."
Instead, the new data show that when weather grew wetter and milder again after Heinrich Event 4, Cro-Magnon populations were able to expand into many areas that Neanderthals previously had all to themselves.
And, it appears, the Cro-Magnon people were better at exploiting the region's resources than Neanderthals were, probably because these anatomically modern humans had more refined technologies and social networks, Banks speculated.
Debate is sure to continue, said anthropologist Henry Harpending of the University of Utah in Salt Lake City, because that's what scientists do. But in his mind, the new study paints a clearer-than-ever picture of what happened in Europe tens of thousands of years ago.
"I don't foresee it being a lively issue for very long," he told Discovery News. "In my mind, this puts it to rest."