Raw material and regionalization in stone age Eastern Africa

Stone tools are the dominant artifact type at Paleolithic sites, and the kinds of stone tools used and their methods of manufacture form some of the richest datasets to assess temporal and geographic patterning in hominin behavior. Using these datasets to compare different lithic assemblages requires comprehensive analytical frameworks that be applied across multiple sites, but this is complicated by the varied nature of the different rock types used in the past. The bedrock lithology of eastern Africa is particularly varied, and we show for a range of Early Pleistocene-to-Holocene-aged archaeological sites that the type and frequency of raw material used, particularly quartz, has significant impacts on a number of typological, technological, and metric variables used to measure variation across time and space, severely weakening our abilities to assess the extent to which past geographic variation in the archaeological record in particular can be attributed to hominin behavior or bedrock geology. Convergence (homoplasy) in particular may be difficult to discern, as even similar behaviors resulting from shared cultural traditions (homology) may result in very different looking artifact types because of the nature of the rock types used.