by Traci Watson on 12 December 2011

Science Now: Up to the Minute News from Science

Stand upright, cool off. That’s long been touted as one of the benefits of our ancestors becoming bipedal in a hot and sunny world. But now researchers have poured cold water on the idea. A team examined how our ancient relatives, who were most likely covered with a thick pelt of hair, would fare while walking briskly in a sizzling place like the African savanna. The body dimensions used in the model—30 kg for females, 55 kg for males—were based on a group of early human ancestors, or hominins, such as Australopithicus afarensis, the species that includes the famous Ethiopian fossil “Lucy.” The models showed that a 30-minute trek put hairy hominins at risk of heat stroke whether they were four-legged or erect , according paper published online today in the Proceedings of the National Academy of Sciences.

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