Heritage Cases

Much of the robust evidence for the early emergence of modern human behaviour, including consistent use of marine resources, in the African Middle Stone Age comes from a series of sites along the southern Cape coastline, South Africa. They include Pinnacle Point (sampling permit applied for through Heritage Western Cape) and Klasies River Mouth. Both the nature of marine resource use and the climatic and environmental contexts of these sites from the Last Interglacial into Marine Isotope Stages 4 and 3 has been a long-standing focus of attention. I aim to construct a seasonally-resolved record of Pleistocene and Holocene sea surface temperatures (SSTs) for the south coast of South Africa using oxygen isotope analyses of archaeological shells from such sites. Given the strong connections between ocean and atmospheric conditions in this region, coastal SSTs, in addition to reflecting global temperature change, are also affected by regional-scale climate dynamics, including prevailing wind variability and seasonal upwelling of cold waters. Thus a record of seasonal SSTs promises to improve our knowledge of the environmental backdrop for the evolutionary origins of modern human behaviour during the Middle Stone Age (MSA). Methods Previous research by Nicholas Shackleton, Francis Thackeray, Mariagrazia Galimberti and others, has demonstrated the utility of the gastropod Turbo sarmaticus for palaeoclimate research but development of this archive has been limited by methodological obstacles, including adequate understanding of the growth environment, and detection of diagenesis. One shortcoming is understanding how the species records intra-annual temperature variations. Modern calibration data from live-captured molluscs will be used to assess the archaeological data. For archaeological samples, I have developed a method for detecting diagenesis using FTIR spectroscopy using an FTIR-ATR instrument at the Research Laboratory for Archaeology (RLAHA) at the University of Oxford. High resolution sampling for δ18O analysis is possible with a micromill based at the University of Oxford. This instrument is a drill mounted to a microscope, and allows for comparatively greater resolution sampling than with a standard hand operated drill. Approximately 0.5 mg of powder is extracted for each sample, which is sufficient for both the FTIR and δ18O analyses. The drill bit penetrates less than 1/10th of a millmetre into the surface of the shell, minimising any distortions to the morphology of the shells. Outcomes Currently, the drivers of southern African MSA cultural innovations such as the Howiesons Poort lithic tradition are obscure because of a lack of sufficiently detailed, well-dated environmental data for the Late Pleistocene. The long, continuous shell midden deposits along the south coast, inter-bedded with cultural material, provide an opportunity to assess the impact of changes in regional-scale climate systems on local environments and human populations in the Cape. Using collections from several sites, I aim to build up a spatial picture of changing sea surface temperatures and environmental conditions along the south coast during the last glacial cycle and the Holocene. In addition the region has a growing number of well-dated palaeo-environmental archives such as speleothems with which to compare my results. This research will have applications for the study of global climate change by providing insights into the dynamics of the Agulhas Current and the westerly wind system. I will also engage with questions about the differences in foraging strategies between the MSA and LSA, including seasonal of occupation and foraging efficiency.