Many extraordinary changes in anatomy and behavior occurred in the 5–7 million years since our lineage split from the lineage that gave rise to the chimpanzees. Fossils tell us a great deal about those changes, especially when high-quality material such as Lucy or Ardi is available, but in general this is an area in which fossils are hard to come by and there is a lot of speculation. Speculation is especially common when we try to explain the reasons behind the evolution of a particular trait. Why, for example, did language evolve? It is easy enough to think of a scenario in which natural selection favors some ability to communicate—maybe language arose to facilitate group hunting. There are plenty of plausible ideas on the subject, but, in most cases, no evidence, so it is impossible to distinguish among competing hypotheses. We can, however, be confident that the events that produced language occurred in Africa, and, through paleontological studies of past environments, we can conclude that humans evolved in an environment similar in many ways to today’s East African savanna.