<P> In Africa, there is a distinct difference in the tools made before and after 600,000 years ago with the older group being thicker and less symmetric and the younger being more extensively trimmed . This may be connected with the appearance of Homo heidelbergensis in the archaeological record at this time who may have contributed this more sophisticated approach . </P> <P> The primary innovation associated with Acheulean hand - axes is that the stone was worked symmetrically and on both sides . For the latter reason, handaxes are, along with cleavers, bifacially worked tools that could be manufactured from the large flakes themselves or from prepared cores . </P> <P> Tool types found in Acheulean assemblages include pointed, cordate, ovate, ficron, and bout - coupé hand - axes (referring to the shapes of the final tool), cleavers, retouched flakes, scrapers, and segmental chopping tools . Materials used were determined by available local stone types; flint is most often associated with the tools but its use is concentrated in Western Europe; in Africa sedimentary and igneous rock such as mudstone and basalt were most widely used, for example . Other source materials include chalcedony, quartzite, andesite, sandstone, chert, and shale . Even relatively soft rock such as limestone could be exploited . In all cases the toolmakers worked their handaxes close to the source of their raw materials, suggesting that the Acheulean was a set of skills passed between individual groups . </P> <P> Some smaller tools were made from large flakes that had been struck from stone cores . These flake tools and the distinctive waste flakes produced in Acheulean tool manufacture suggest a more considered technique, one that required the toolmaker to think one or two steps ahead during work that necessitated a clear sequence of steps to create perhaps several tools in one sitting . </P>

The acheulian biface or hand axe is a basic tool of the acheulean tradition