Variability in Silcrete Heat Treatment at Klein Kliphuis Shelter, South Africa, and Its Role in Core Reduction

Silcrete heat treatment was the earliest known transformative process enhancing the mechanical properties of materials. Its study has implications for our understanding of the cultural evolution of early humans in the Middle Stone Age and southern Africa. Here, we analyze a silcrete assemblage from the South African site Klein Kliphuis. We first investigate the relative prevalence of heat treatment in assemblage and then the position of heat treatment within reduction sequences. We found that similar to 60% of all silcrete was heat-treated prior to knapping in one post-Howiesons Poort assemblage and similar to 85% in two Howiesons Poort assemblages. However, heat treatment early-on was not the only strategy present in the site. Late-stage heat treatment was occasionally deployed to extend the utility of small cores. This finding emphasizes the ability of early anatomically modern humans in Africa to adapt their tool making behavior to changing economic conditions related to raw materials quality and availability.