By contrast, when a chimpanzee tries to walk upright, its feet stay wide apart, its center of gravity shifts side-to-side, and it awkwardly teeters for only a short time. Lucy and other members of ...

so they stand and walk with their feet wide apart. Their gluteal abductors are also much weaker than ours, so they have to rock their whole body from side to side during each step, in order to ...