Laetoli Pliocene hominid footprints and bipedalism

Abstract

The ability to stand upright and walk on two legs is widely recognized as a crucial hominid adaptation that had profound effects on the course of human evolution. The relief of the upper limb from the task of supporting the trunk in locomotion would have permitted the efficient carriage of food, infants and later tools and weapons. Any or all of these activities could, it is believed, have improved the differential survival of early hominids. Precisely when upright stance and bipedal gait were first acquired within the hominid evolutionary line is not known, and so the discovery of apparently bipedal footprints of Pliocene age at site G, Laetoli, Tanzania is important in itself^1,2. A study of the footprints, reported here, has shown that when these hominids walked, they transmitted their body weight and the forces of propulsion to the ground in a manner very similar to that of modern man.