Modeling Provides Clues To Climate Change And Neanderthal Extinction

Computational modeling that examines evidence of how hominin groups evolved culturally and biologically in response to climate change during the last Ice Age also bears new insights into the extinction of Neanderthals.

“To better understand human ecology, and especially how human culture and biology co-evolved among hunter-gatherers in the Late Pleistocene of Western Eurasia (ca. 128,000-11,500 years ago) we designed theoretical and methodological frameworks that incorporated feedback across three evolutionary systems: biological, cultural and environmental,” said Michael Barton of Arizona State University and lead author of the study.

“One scientifically interesting result of this research, which studied culturally and environmentally driven changes in land-use behaviors, is that it shows how Neanderthals could have disappeared not because they were somehow less fit than all other hominins who existed during the last glaciation, but because they were as behaviorally sophisticated as modern humans,” Barton continued.

Details of the complex modeling experiments conducted at Arizona State University and the University of Colorado Denver will be published in the December issue of the Springer journal Human Ecology, available online 17 November 2011.

“It’s been long believed that Neanderthals were outcompeted by fitter modern humans and they could not adapt,” said co-author Julien Riel-Salvatore of the University of Colorado Denver. “We are changing the main narrative. Neanderthals were just as adaptable and in many ways, simply victims of their own success.”

The interdisciplinary team of researchers used archeological data to track behavioral changes in Western Eurasia over a period of 100,000 years and showed that human mobility increased over time, probably in response to environmental change. According to Barton, the last Ice Age saw hunter-gathers, including both Neanderthals and the ancestors of modern humans, range more widely across Eurasia searching for food during a major shift in the Earth’s climate.

The scientists utilized computer modeling to explore the evolutionary consequences of those changes, including how changes in the movements of Neanderthals and modern humans caused them to interact – and interbreed – more often.

According to Riel-Salvatore, the study offered further evidence that Neanderthals were more flexible and resourceful than previously assumed.

“Neanderthals had proven that they could roll with the punches and when they met the more numerous modern humans, they adapted again,” Riel-Salvatore said. “But modern humans probably saw the Neanderthals as possible mates. As a result, over time, the Neanderthals died out as a physically recognizable population.”

To reach their conclusion, the researchers ran a computer program for the equivalent of 1,500 generations showing that as Neanderthals and modern humans expanded their yearly ranges, the Neanderthals were slowly absorbed by more numerous modern humans.

“We tested the modeling results against the empirical archaeological record and found that there is evidence that Neanderthals, and moderns, did adapt their behaviors in the way in which we modeled,” explained Barton. “Moreover, the modeling predicts the kind of low-level genetic admixture of Neanderthal genes that are being found in the newest genetic studies just now being published.”

“In other words, successful behavioral adaptations to severe environmental conditions made Neanderthals, and other non-moderns about whom we know little, vulnerable to biological extinction, but at the same time, ensured they made a genetic contribution to modern populations,” Barton said.