Flexi Says: Humans evolved during the later Cenozoic. New fossil discoveries alter the details of what we know about the evolution of modern humans, but the major evolutionary path is well understood. Humans evolved from primates, and apes and humans have a primate common ancestor. About 7 million years ago, chimpanzees (our closest living relatives) and humans shared their last common ancestor. Animals of the genus Ardipithecus, living roughly 4 to 6 million years ago, had brains roughly the size of a female chimp. Although they lived in trees, they were bipedal. Standing on two feet allows an organism to see and also to use its hands and arms for hunting. By the time of Australopithecus afarensis, between 3.9 and 2.9 million years ago, these human ancestors were completely bipedal and their brains were growing rapidly. The genus Homo appeared about 2.5 million years ago. Humans developed the first stone tools. Homo erectus evolved in Africa about 1.8 million years ago. Fossils of these animals show a much more human-like body structure, which allowed them to travel long distances to hunt. Cultures begin and evolve. Homo sapiens, our species, originated about 200,000 years ago in Africa.