Why do people walk on two legs? Just ask a chimp

By Merek Siu

Before stone tools and bigger brains, the first step toward making humans human was a step on two legs.

What prompted our ancestors to start striding upright is hotly debated.

"When you answer that question, you're really answering the question of how did we become human," said Michael Sockol, lead author on a recent study addressing the origins of bipedalism, or walking on two legs.

But by studying chimps, researchers found that energy used to walk upright or on all fours varied, enough to suggest it played a role in making us bipedal.

Variation in energy spent provided a lever for natural selection, and energy efficiency played a role in getting our ancestors to walk on two legs. The research initiated by Sockol, an anthropology graduate student at the University of California, Davis, was published last month in Proceedings of the National Academy of Sciences.

"Up to now, we had no evidence that energy was even involved. Now we do," said Sockol.

The paper and its hypothesis that energy played a role in the origin of walking upright stir up strong responses.

"The paper is a technical tour de force and provides valuable new data and insights on the energetic advantages of bipedalism," said William Jungers, professor of anatomical sciences at Stony Brook University in New York.

Full story at Sacramento Bee: