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Walking on two legs easier than walking on four

WASHINGTON: Walking upright required considerably less effort from early man then “knuckle-walking”, according to research being released this week that explains why humans today, unlike most primates, walk on two legs.

The new study, ‘Chimpanzee Locomotor-Energetics and The Origin of Human Bipedalism’ hypothesises that walking on two legs, or bipedalism, evolved because it required less energy than scampering on all fours. It is to be made public this week in the Proceedings of the National Academy of Sciences.

“For decades now researchers have debated the role of energetics and the evolution of bipedalism,” said David Raichlen, an assistant professor of anthropology at The University of Arizona, who was one of the lead scientists on the study. The researchers wrote they used “biomechanical modelling” to simulate the primates’ gaits. Scientists studied the gaits of four adult humans walking on a treadmill, and also studied five chimpanzees that were trained to walk quadrupedally [on four legs] as well as bipedally [on two legs].

Raichlin and his colleagues found that humans walking on two legs used just one-fourth the energy that chimpanzees that knuckle-walked did. Raichlin and his colleagues said biomechanical modelling found that on average, chimpanzees use the same amount of energy on two legs as on four, but said there was variation from animal to animal. “We were able to tie the energetic cost in chimps to their anatomy,” said Raichlen. “We were able to show exactly why certain individuals were able to walk bipedally more cheaply than others,” he said. afp

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