Lithic heat treatment and behavioral evolution during the South African Middle Stone Age

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The objective of the proposed study is to investigate the earliest known appearance of intentional heat treatment of lithic raw material in the South African Middle Stone Age (MSA). Over the past couple decades, southern Africa has become a key region for investigating the appearance of technological innovation and symbolic behavior. Heat treatment, i.e. the deliberate transformation of a material’s properties by heat, is believed to be a part of the evolution of Homo sapiens towards a more complex and modern behavior. However, the recent discussion about the role of heat treatment in this process lacks a solid basis. Neither the exploited material (silcrete) and its thermal transformations, nor the conditions applied by the treatment s authors are known. We propose a two-pronged approach: [1] The direct assessment of the occurrence of heat treatment, the applied temperatures, the used silcrete types and the evolution of the process throughout the MSA and [2] an experimental investigation on the properties and temperature-dependent transformations, including potential effective temperatures, durations and environments. The direct comparison between experimental data and the data obtained from the South African artifacts will produce new data on the cognitive processes and technological knowledge of the groups of Homo sapiens.