Journal of Archaeological Science (1999) 26, 571-585
By the late Pliocene humans had made the revolutionary discovery of stone tools. This was the Oldowan stone tool industry - the oldest known assemblages of which are found at Gona, Ethiopia 2.6-2.5Ma.Oldowan assemblages have hammerstones, simple cores and unmodified flakes. There are no specific tool types because the shapes are accidental rather than planned and the objective seems just to be to produce sharp edges for slicing scavenged meat. By 1.4Ma a new industry appears - the Acheulean (Konso, Ethiopia) artifacts of which will span a million years. Unlike the Oldowan the forms of Acheulan tools appear to have been preconceived. One tool type - the symmetrical hand axe which has been flaked from two faces is the Acheulean's defining characteristic.
Exclusively Oldowan assemblages are found Eastern Asia from 1.8Ma in Europe at 0.78Ma (Atapuerca, Spain) and possibly 1.4Ma (Orce, Spain), Acheulan assemblages don't penetrate Europe until 0.5-0.4Ma. It can be speculated that as well as a technological difference these different technologies could represent species differences. Arribas and Palmqvist point to H. ergaster as the Oldowan bearing species.