The production of bifacial stone tools began in East Africa at least as early as 1.75 million years ago. This was demonstrated by the Konso deposit in Ethiopia, which yielded bifaces, axes and splintery picks. It is therefore slightly more recent than the first fossils attributed to Homo erectus. While some African deposits are famous for their considerable accumulations of bifaces, these tools may represent only a small percentage of the artifacts present in Acheulean assemblages. Sometimes, at the same site, as at the Thomas quarry in Casablanca, Acheulean and Oldowayan assemblages alternate in the same stratigraphic sequence.
Outside Africa, bifaces appear around 1.4 million years ago, at Ubeidiya in Israel and Attirampakkam in southern India. The Acheulean period thus began in Eurasia after hominins had colonized the continent. This time lag between the arrival of the first inhabitants and the spread of Acheulean is generally considered to be responsible for the establishment of the "Movius line", which separates regions close to Africa where bifaces predominate from those where they remain rare or even totally absent, in Europe or the Far East.
In Europe, the first bifaces are known between 700,000 and 650,000 years BC. The late onset of the European Acheulean could be associated with the arrival from Africa and/or the Near East of a new form of hominin, Homo rhodesiensis/heidelbergensis. But it could also be the result of a separate invention. Asian regions beyond the Movius Line provide examples of such technical convergence. Certain lithic assemblages from Central and Eastern Europe, on the other hand, remain totally devoid of bifaces.
From isotopic stage 9 onwards, the proportion of bifaces in European sites decreases, while the Levallois debitage technique begins to take on increasing importance. However, bifaces do not disappear completely and, until the end of the Middle Paleolithic, they can occasionally be observed in very small proportions within lithic assemblages.
