Research master thesis | Archaeology (research) (MA/MSc)
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Gaining insight into the origins and nature of fire use in the Palaeolithic has important implications for the understanding of various aspects of hominin behaviour and cognition. Major topics...Show moreGaining insight into the origins and nature of fire use in the Palaeolithic has important implications for the understanding of various aspects of hominin behaviour and cognition. Major topics within the field of fire research include: the timing of the first (controlled) use of fire, fuel use (bone vs. wood) and its relation to different tasks and adaptive strategies, pyrotechnology (i.e. fire use as a tool), and cooking. Within the study of fire use in the Palaeolithic there is a strong reliance on patterns of presence and absence of fire indicators. Therefore, understanding the way in which fire traces are affected by taphonomy and being able to correctly identify them in the Palaeolithic record are important prerequisites for valid interpretations of hominin fire-related behaviour and cognition. While most other post-depositional processes are nowadays taken into account, diagenesis (i.e. chemical processes) is often still overlooked. This is unfortunate since a recent study by Braadbaart et al. (2009) indicated that exposure to alkaline conditions (pH values >7) can severely affect the preservation potential and temperature signal of charcoal in the archaeological record. This will affect interpretations based on patterns of fire indicators, as well as interpretations linking temperatures to specific uses of fire. This thesis aims to contribute to the study of fire use in the Palaeolithic by exploring the influence of pH on the preservation potential and temperature signal of charred bone and wood. Bone and wood samples were charred to a range of temperatures (unheated, 190º, 250º, 340º, 600ºC), and exposed to pH solutions representing acidic (pH 3), neutral (pH 7) and alkaline (pH 12) conditions. The samples were incubated for a period of approximately six months. After incubation, the samples were analysed to determine chemical composition (using XRF and TGA), temperature signal (using TGA and reflectance analysis), and mass loss. Results were compared to existing data on unexposed charred bone and wood. This study indicated that charred bone and wood are affected by all pH values, resulting in mass loss, fragmentation, and colour and consistence changes. Temperature inferences for charred bone, based on TGA and/or colour, were deemed unreliable. Temperature inferences for charred wood, based on reflectance analysis, were only affected under alkaline conditions. Based on these results, it is suggested that more attention should be paid to the influence of pH on the preservation potential of fire remains, and that pH should be recognised as a legitimate cause for absence of evidence of fire use.Show less
