The adoption of heat treatment as a strategy to improve the workability of stone has long been observed in the archaeological record, commencing in Australia as far back as the late Pleistocene. Several studies have suggested that heat- treated cores tend to produce thinner and sharper tools, however the impact of this technique on their performance over extended periods of use is less well known. It has been hypothesised that the process reduces edge durability due to the increased brittleness of the raw material and the narrower edge profiles that it produces. When used to process hard materials such as wood or bone, heated edges are assumed to exhibit a more rapid loss of performance, leading some to suggest that the technique might have been selectively deployed. The aim of this present study is to test whether heated tools have higher cutting efficiency in a controlled experimental setting and to determine to what extent the performance of heated and unheated tools decline over th
South Africa’s Still Bay technocomplex (77–70 ka) is an early example of a technological system organised around the production of bifacial points. Noting the diversity of raw materials used and the frequency of non-local raw materials found among excavated bifacial point assemblages, numerous researchers have argued that Still Bay foragers were highly mobile. This pattern, however, is in contrast to that observed in some open-air surface Still Bay assemblages, where raw material diversity among bifacial points is low and local rocks dominate. We resolve this apparent discrepancy by combining information on raw material distribution, least-cost path analysis, and artefact data from two rock shelters and numerous open-air sites located along the Doring and Olifants Rivers in South Africa. The results demonstrate that raw material selection for bifacial point production was responsive to geological resources within river catchments but that bifacial points were transported regularly
Discussions of heat treatment in the southern African Middle Stone Age often focus on the importance of this innovation to the development of complex technologies and the evolution of modern human cognition. Debates regarding the context of silcrete heat treatment typically include the amount of time and resource investment needed, and when the earliest occurrences of heat treatment appear in the archaeological record. However, silcrete is a heterogeneous material and the potential effects of this heterogeneity on the thermal transformations that occur during heat treatment are not well established. We undertook a series of controlled experiments using direct transmission near-infrared spectroscopy on South African silcretes from multiple sources heated to a range of maximum temperatures to examine the degree of heterogeneity in starting structural content and the evolution of thermal transformations. We found that material source is an important determinant of starting concentrations
Geological analysis reveals what makes the famed megaliths of Stonehenge in southern England extremely durable that they resist centuries of weathering.