The earliest hominid fossil we have was found in Africa and dates back to 4.4 million years ago. This fossil belongs to the earliest group of hominids called australopithecines. This group, which lasted for about 3 million years and diversified into several species, was characterized by bipedalism; fossil footprints have been found. However, australopithecine brain size was not markedly larger than that of their non-hominid ancestor. Skull and dental characteristics were more ape-like. The reasons for the evolution of bipedalism are not clear. It may have been due to spending more time on the ground and having to move through the rather open African savanna.