How has Lucy changed our perceptions about the evolution of the family tree?
Donald Johanson: The major impact which Lucy has had is on a previous scenario of human origin where people felt that there were a number of events, evolutionary changes, which all went together. That our ancestors stood up to free their hands so that they could make and use stone tools. In order to make and use stone tools, they had to have large brains. This has view has been pretty much a view that’s dominated human origin study, ever since it was suggested by Darwin in the middle 1800s. Here comes Lucy, about 3.5 million years old. She has a very small brain, not much bigger than that of a chimpanzee, and we have never found any stone tool, stone artifacts, associated with her species. Yet she is walking upright. So it appears that upright, bipedal posture and gait, walking on two legs, precedes by perhaps as much as a million and a half years, the manufacture of stone tools and the expansion of the brain. That means that there has to be a major new way of looking at what it was th
