Investigating raw material selection for stone tool making with material sciences

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The study of raw materials for stone tool making has important implications for our understanding of past people. Specifically, changes in the spectrum of stone tool raw materials through time have been interpreted as markers of changing mobility, economy or technology-driven selection. Two South African Middle Stone Age (MSA) sites, Diepkloof Rockshelter and Sibudu Cave (~100-50 ka), document such shifts throughout their sequence particularly well. Do these changes reflect changing accessibility of different raw materials, perhaps changing territoriality? Or, alternatively, did the foragers of the later part of the South African MSA specifically selected raw materials for tool making? These questions can be answered by investigating whether the qualities of different raw materials for making and/or using specific tools are correlated with their preferential selection. The aim of this research project is to shed light on these correlations by studying the mechanical properties relevant to tool knapping (knapping quality) and use (resistance to abrasion and impact fracture formation). The choices Diepkloof and Sibudu foragers actually made during raw material provisioning will be interpreted in the light of the results of the mechanical data. For this, we have developed a new method for quantifying Knapping quality and the likelihood of fracturing, based on material science. By using this new model, combined with quantitative use-experiments, this project seeks to uncover some of the fundamental mechanisms that drive tool stone selection at a time that is crucial to the evolution of early modern humans.