The earliest known Oldowan tools yet found date from 2.6 million years ago, during the Lower Palaeolithic period, and have been uncovered at Gona in Ethiopia. After this date, the Oldowan Industry subsequently spread throughout much of Africa, although archaeologists are currently unsure which Hominan species first developed them, with some speculating that it was "Australopithecus garhi", and others believing that it was in fact "Homo habilis". "Homo habilis" was the hominin who used the tools for most of the Oldowan in Africa, but at about 1.9-1.8 million years ago Homo erectus inherited them. The Industry flourished in southern and eastern Africa between 2.6 and 1.7 million years ago, but was also spread out of Africa and into Eurasia by travelling bands of "H. erectus", who took it as far east as Java by 1.8 million years ago and Northern China by 1.6 million years ago. Eventually, more complex Mode 2 tools began to be developed through the Acheulean Industry, named after the site of Saint-Acheul in France. The Acheulean was characterised not by the core, but by the biface, the most notable form of which was the hand axe. The Acheulean first appears in the archaeological record as early as 1.7 million years ago in the West Turkana area of Kenya and contemporaneously in southern Africa. The Leakeys, excavators at Olduvai, defined a "Developed Oldowan" Period in which they believed they saw evidence of an overlap in Oldowan and Acheulean. In their species-specific view of the two industries, Oldowan equated to "H. habilis" and Acheulean to "H. erectus". Developed Oldowan was assigned to "habilis" and Acheulean to "erectus". Subsequent dates on "H. erectus" pushed the fossils back to well before Acheulean tools; that is, "H. erectus" must have initially used Mode 1. There was no reason to think, therefore, that Developed Oldowan had to be "habilis"; it could have been "erectus". Opponents of the view divide Developed Oldowan between Oldowan and Acheulean. There is no question, however, that "habilis" and "erectus" coexisted, as "habilis" fossils are found as late as 1.4 million years ago.