In this video, Don Johanson describes finding the knee joint in Hadar, Ethiopia, that first indicated a bipedal hominid had lived 3 million years ago. His subsequent expedition led to the discovery of Lucy, a 40 percent complete skeleton of a new species of hominid, now known as Australopithecus afarensis. The final piece of the puzzle was a skull from the same site, which clearly demonstrated that Lucy's kind were small-brained, although they walked upright.
© 2015 PBS & WGBH Educational Foundation. All rights reserved.