July 17, 2007

Upright-Walking Humans More Efficient Than Chimps

Treadmill tests show that humans expend only a quarter of the energy walking that chimps do. Karen Hopkin reports.

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When it comes to locomotion, being bipedal is not a bad way to go. This week, a team of researchers report that humans spend only about a quarter of the energy walking on two legs that chimps spend knuckle-walking on all fours.

The scientists…led by Herman Pontzer of Washington University in St. Louis...measured the amount of oxygen consumed as their subjects walked on a treadmill. They found that chimps took in about the same amount of oxygen whether they were galloping on all fours or waddling upright. But human volunteers, pound for pound, were more efficient than the chimps. The results appear in the current issue of the Proceedings of the National Academy of Sciences.

One chimp…a 33-year-old female…was actually more efficient tooling along on two legs than she was knuckle-walking on four. This particular ape had a longer stride than the other chimps…and being able to get where you want to go using fewer steps translates into less energy expenditure. That kind of energy conservation could be what prompted our human ancestors to stand up and walk on their own two feet. That’s right—bipedalism was a *gait* way of evolution.

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