Topic ID #34321 - posted 12/23/2014 1:46 AM

Fragile bones of modern humans result from physical activity



Jennifer Palmer

Webmaster
Fragile bones of modern humans result from reduced physical activity

The comparatively light bone structure of modern humans compared to early human species and other modern primates may be due to the modern abandonment of the constant physical activity that was inherent in the life of early hunter gathers, according to an international team of researchers. This knowledge may aid in prevention of osteoporosis and hip fracture in the elderly.

"We set out to test three potential explanations for modern human gracility and any one of them would have been interesting," said Timothy M. Ryan, associate professor of anthropology and information science and technology, Penn State. "What we found was the most interesting."

The most plausible explanation, he said, is that a lack of constant physical activity causes the bone in the head of the femur -- the long bone in the thigh -- to become thinner and lighter than that found in more mobile populations or modern primates such as chimpanzees, gorillas and orangutans. The other two possible explanations, that humans and nonhuman primates have different bone structure because of genetics, with humans evolving to a lighter, more gracile structure, or that the large joint surfaces required for upright, two-legged movement decrease the strain on bone and therefore the development of strong bones, do not appear to be true.

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