IT WAS one of the features that was supposed to be unique to the human evolutionary branch. We walk upright, while chimps and gorillas “knuckle-walk” on all fours. Now it seems that we didn’t evolve bipedalism from knuckle-walking: apparently walking upright arose far earlier in our history, when our ancestors were still in the trees, and has died out in our closest relatives.
Several scenarios have been proposed to explain why we came to walk on two legs, from the idea that it helped our ancestors feed and carry infants more efficiently, to the theory that it reduced our exposure…
