Walking Chimps Move in Surprisingly Similar Ways to Humans

When we humans strut our stuff, we do it by coordinating the movements of our hips and upper bodies. As the pelvis rotates forward, the trunk moves in the opposite direction, cancelling out angular momentum and reducing the amount of energy burned while walking. Finally, swinging arms counterbalance the sway of the hips, completing the characteristic human gait.
 Chimpanzees, on the other hand, can be trained to walk on two hind legs and will occasionally do it in the wild, but it is not their preferred means of getting around. When they do walk upright, their compact trunks and tall, wide hips cause them to stoop. As they make their way forward, the trunk appears rigid while the swing of the hips and arms seems overly pronounced and somewhat clumsy.
 Pairing that observation with studies of chimp bone structure, researchers had long assumed that our closest relatives lack the counter-rotations characteristic of human motion. Following this logic, scientists also concluded that human ancestors prior to Homo erectus—whose morphology shares commonalities with chimps—likely walked that way, too. Until now, however, no one ever verified that assumption.
And as it turns out, it is not correct.