DNA testing and the shape of the femur found in the cave show that the bone belonged to a late adolescent or adult Neandertal. The thickness of the bone and other aspects of its shape and form suggest that a shift in weight-bearing patterns was taking place.
"The shafts of long bones respond to the kinds of mechanical stresses that they're subjected to," Trinkaus said. "What we're looking at here is greater reinforcement in the front-to-back direction."
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This reinforcement is associated with greater mobility, particularly for hunter-gatherers, he says.
"You see them [femurs] very much exaggerated in early modern humans around 25,000 years ago, at a time, certainly in Europe, when people were very mobile," he said. "And then by 15,000 years ago, when for a variety of reasons, people are becoming considerably less mobile and their territories are becoming smaller, we see a decrease in this front-to-back reinforcement, so its something that's plastic [changeable], it's not a genetic trait."
Biomechanical studies of how bones respond to stresses raise some questions about this interpretation.
"Using bone cross section shapes to infer that Neanderthals behaved more like modern humans is quite a leap," said Daniel Lieberman, a physical anthropologist at Harvard University in Massachusetts.
"These kinds of inferences are based on a biomechanical model that has been shown to have limitations. If you get a fossil bone, you try to get as much information out of it as you can. But a bone is just a bone, and trying to infer function from form is a very difficult thing in morphology," he said. Morphology is the study of the forms and structures of plants and animals.
The question of how modern humans and Neandertals used the landscape is hotly debated.
One school of thought holds that modern humans migrating into Europe around 40,000 years ago were highly mobile. They shifted campsites on a seasonal basis, moving as different resources became available in different places. In this scenario, once Neandertals found a prime site, they settled in, stayed for long periods of time and exploited the local resources as they became available.
But the new study, published in the new issue of the Proceedings of the National Academy of Sciences, suggests that Neandertals were far more mobile and capable of moving from strictly local resource utilization to a more regional perspective as they expanded their territories.
"What we have evidence for here, and it's certainly not the only evidence, is that late Neandertals were behaviorally evolving in the direction that we see more full blown with modern humans in the upper Paleolithic," said Trinkaus, one of the co-authors of the study. "And this was clearly starting well before there were any modern humans around Europe."
"People tend to look at it in terms of Neandertals and their biology versus modern humans and their biology. And what we're really looking at are changes in the cultural adaptations of these hunter-gatherers," Trinkaus said. "And the cultural advances are taking place semi-independently of who is involved or whether they're Neandertals or modern humans."
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