The most significant biological development was the appearance and evolution of the genus Homo. The oldest species, H. habilis, probably evolved from an australopithecine ancestor in the late Pliocene. The species was present in Africa by 2 million years ago and is known from sites as young as 1.5 million years old. Another extinct species, H. erectus, evolved in Africa, possibly from H. habilis, and is known from sites about 1.6 million years old. H. erectus spread to other parts of the Old World during the early Pleistocene and is known from northern China and Java by roughly 1 million years ago.
Representatives of this group are known from many sites, and these beings constituted the dominant human species for more than a million years.
