Walking On Two Feet…

Did walking on two feet begin with a shuffle ?
Somewhere in the murky past, between four and seven million years ago, a hungry common ancestor of today’s primates, including humans, did something novel. While temporarily standing on its rear feet to reach a piece of fruit, this protohominid spotted another juicy morsel in a nearby shrub and began shuffling toward it instead of dropping on all fours, crawling to the shrub and standing again.


“Metabolic energy is produced by what an animal eats, enabling it to move. But it is a limited resource, particularly for young-bearing females which have to take care of and feed their offspring. Finding food is vitally important, and an animal needs to save energy and use it efficiently,” said Patricia Kramer, a UW research assistant professor of anthropology and co-author of a recent study.

She believes it was an empty belly, along with a need to conserve energy, that prompted that early ancestor to shuffle. “Hunger. It is always hunger,” said Kramer. “There is nothing that will get you to do something you don’t want to do other than food. That’s why we bribe animals with food to train them.”


Chimpanzees are humans’ closest relatives. They basically walk on all fours, partially resting their weight on the knuckles of their hands. “A chimp’s body plan is very much like that of a primitive ape, and our last common ancestor probably had a body like that of a chimp. Modern humans are different with long legs and a big head. So chimps are a good place to start,” Kramer said.




* The study was published in the American Journal of Physical Anthropology


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