September 2011, Daily News

Neanderthals Vanished Because of Their Own Success, Suggests Study

Thu, Nov 17, 2011

Using data obtained from the archaeological record, a team of researchers at Arizona State University and the University of Colorado, Denver, conducted experiments using complex computer modeling to analyze evidence of how human hunter-gatherers responded culturally and biologically to the dramatic changes that took place during the last Ice Age. The results showed, among other things, that the Neanderthals, thought by many scientists to have become extinct at least in part because of their inadaptability and inability to compete with the expanding presence of modern humans, may have actually been victims of their own success. 

The researchers used the archeological record to track human behavioral changes in Late Pleistocene (126,000 - 10,000 B.P.) Western Eurasia over a period of 100,000 years and across the equivalent of 1,500 generations of human hunter-gatherers. They applied computer modeling to determine the evolutionary consequences of cultural and biological changes, which included how changes in the movements of modern humans and Neanderthals caused them to interact and interbreed with each other. The results showed that human mobility during the environmental changes associated with the Ice Age increased over time, likely in response to those environmental changes. The modeling suggested that the last Ice Age caused the ancestors of modern humans -- and Neanderthals --  to widen their ranges across Western Eurasia in search of new resources as the climate shifted. 

According to study co-author Julien Riel-Salvatore of the University of Colorado, Denver, this provided new evidence that Neanderthals were more adaptable and resourceful than previously thought. Moreover, the study results suggested that the Neanderthals were gradually absorbed within the expanding modern human populations until they eventually disappeared as a distinctly separate human population and phenotype.

Says Riel-Salvatore, "It's been long believed that Neanderthals were outcompeted by fitter modern humans and they could not adapt. We are changing the main narrative. Neanderthals were just as adaptable and in many ways, simply victims of their own success. Neanderthals had proven that they could roll with the punches and when they met the more numerous modern humans, they adapted again. But modern humans probably saw the Neanderthals as possible mates. As a result, over time, the Neanderthals died out as a physically recognizable population."

Michael Barton, study co-author and expert on archaeological applications to computer modeling at Arizona State University, agrees. "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," said 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.

Continued Barton, "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."

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Computer agents (colored dots) simulating prehistoric hunter-gatherer groups are superimposed over a map of Late Pleistocene western Eurasia. Gray shows Pleistocene land area with lowered sea levels, black lines show modern coastlines, white areas show ice sheets. The blue dots represent groups of "modern" humans, red dots represent groups of Neanderthals, and yellow dots represent groups with biological mixtures of modern and Neanderthal genes. This is a snapshot of the simulation after hundreds of cycles in which the hunter-gather groups have higher mobility in response to changing glacial climate.   Credit: Michael Barton/Arizona State University

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The research was funded by the National Science Foundation, a Fulbright Senior Research Fellowship and a Fulbright Graduate Student Fellowship. The paper is published in the December issue of Human Ecology as Modeling Human Ecodynamics and Biocultural Interactions in the Late Pleistocene of Western Eurasia, available online on November 17, 2011. It is co-authored by Michael Barton, Arizona State University; Julien Riel-Salvatore, assistant professor of anthropology at the University of Colorado Denver; John Martin Anderies, associate professor of computational social science at ASU in the School of Human Evolution and Social Change and the School of Sustainability; and Gabriel Popescu, anthropology doctoral student at the School of Human Evolution and Social Change, Arizona State University.

Cover Photo, Top Left: Neanderthal skull cast, originally found in St. Michael's Cave. Nathan Harig, Wikimedia Commons