Have you ever wondered why humans walk on two legs, while pretty much all other animals prefer four?  Most human evolution researchers think we started to walk upright through a process beginning with "knuckle walking" on land - the way that chimps and gorillas (and maybe some of the Naked Scientists team!) walk today.Sumatran orangutan

This change was thought to have happened when our ancestors left the forests of East Africa and moved onto the grasslands. But researchers from the University of Liverpool have come up with some evidence to suggest that we actually learned to walk upright by foraging in treetops for food, in a paper published in the journal Science.

Their studies of Sumatran orang-utans have led them to the conclusion that knuckle walking is quite a recent development for chimps, and that the ancient great apes actually spent more time on two legs in trees, holding onto branches for support.  So us humans may never have gone through a knuckle dragging stage at all, and skipped straight from tree living to two feet on the ground.

One of the researchers, Professor Robin Crompton explains that "Walking upright on two legs, gripping branches with the feet and balancing themselves by holding or touching higher branches with their hands is actually a very effective way of moving on smaller branches. It helps to explain how early human ancestors learnt to walk upright whilst living in the trees and how they would have used this way of movement when they left the trees for a life on the ground."


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