Components of Acheulean lithic assemblage variability at Olorgesailie, Kenya

Acheulean large cutting tools (cleaver, handaxe, knife, and pick) have pronounced and unexplained regional and temporal differences in size, shape, refinement, and manufacturing strategies. This thesis systematically evaluated factors contributing to inter- and intra-assemblage stardardization and variation, using lithic assemblages from the Olorgesailie Formation as a test case. A "Method of Residuals" approach is operationalized and used to examine lithic assemblage variability. The Method of Residuals examines lithic assemblage variation, first by considering simple non-cultural factors including mechanical properties, size and shape of available raw materials, and logistical constraints (distance to raw material sources), and then evaluates more complex behavioral and cultural components of variation such as style. Analyses included identification and description of discrete raw material types used in artifact manufacture; examination of raw material mechanical properties using rock mechanics tests; and assessment of inter- and intra-assemblage morphological variability.;Several conclusions emerge. First, certain raw material types dominate Olorgesailie lithic assemblages. Correlation between raw material preference and physical and mechanical properties implies that Olorgesailie hominids selected those materials with superior properties relating to stone tool manufacture and use. Second, morphological differences between large cutting tools manufactured on different raw material types were identified. Raw material properties generated variability in large cutting tool thickness, stepped flake scar density, and edge angle. Third, large cutting tools from older (Member 1) assemblages were smaller than those from younger (Member 6/7) assemblages. It is posited that Member 1 large cutting tools were initially as large as those in Member 6/7 but became smaller, apparently though use and subsequent rejuvenation through flaking.;The data presented here suggest that factors other than style generated inter- and intra-assemblage variability. In other words, distinct cultural traditions are not observed within or between Olorgesailie assemblages. Because most variability is attributed to raw material and resharpening (reduction) any apparent stylistic component of variability has been removed from the behavioral repertoire of Olorgesailie hominids. The degree to which their behavior resembles that of modern humans is substantially reduced by the results of this analysis. Moreover, these results suggest that the cultural capacities of Acheulean stone-knappers have been consistently overestimated.