Many important hominid fossils have been found in Tanzania, such as 6-million-year-old Pliocene hominid fossils. The genus Australopithecus ranged all over Africa 4 to 2 million years ago; and the oldest remains of the genus ''Homo'' are found near Lake Olduvai. Following the rise of ''Homo erectus'' 1.8 million years ago, humanity spread all over the Old World, and later in the New World and Australia under the species ''Homo sapiens''. ''H. sapiens'' also overtook Africa and absorbed the older archaic species and subspecies of humanity.