Paleonthropology

Human skeleton became lighter over time

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Science  02 Jan 2015:
Vol. 347, Issue 6217, pp. 39-40
DOI: 10.1126/science.347.6217.39-h

CT scans of hand bones from (clockwise from top left): chimp, Australopithecus, Neandertal, modern human.

PHOTO: © AMNH/J. STEFFEY AND BRIAN RICHMOND

Chimp bones are packed with microscopic structures known as spongy bone; modern human bones aren't, increasing risk of fractures and osteoporosis. Two studies propose an explanation for this change: Chirchir et al. found that skeletons from modern chimpanzees, Australopithecus africanus, Neandertals, and early Homo sapiens all had higher densities of spongy bone than modern humans, suggesting that our sedentary lifestyle is to blame. Ryan and Shaw also found lower spongy bone density in the hip joints of ancient farmers compared with hips from nonhuman primates and ancient hunter-gatherers, supporting the idea that a lack of rigorous exercise, not evolutionary pressure, is responsi ble for our weak bones.

Proc. Natl. Acad. Sci., 10.1073/pnas.1411696112(2014), 10.1073/pnas.1418646112(2014).

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