Heritage Cases

Some of the earliest evidence of coastal exploitation by humans anywhere in the world is found in shell midden sites along the southern coast of South Africa dating to the Middle- and Late Stone Age (c. 200-10 kyr BP). Sites such as Blombos, Border, Klasies River and Pinnacle Point caves are widely regarded as vitally important for our understanding of the evolution of anatomically modern humans and the development of ‘modern’ forms of behaviour and cognition (Jerardino and Marean, 2010; Marean, 2010). In previous research on these sites, surprisingly little attention has been paid to the seasonal use of shellfish. My thesis will examine the evidence for the exploitation of marine bivalves by LSA people at Pinnacle Point. The main emphasis will be on the on the season of collection of shellfish, the exploitation strategies employed and the environmental context. My main objectives will be to investigate: (a) The uses of marine bivalves by LSA people: were marine bivalves collected primarily as human food, or were they used as bait for fishing? Were their shells also used as tools, ornaments, and/or exchange items? (b) Chronological variation and seasonality in the use of marine bivalves: were they a constant component of the LSA economy, or a significant element of a particular phase or phases? Did patterns of collection, use and discard change over time? Were bivalves exploited year round or only in a particular season? What factors conditioned and influenced changes in these patterns through time? Did the patterns differ from site to site, and if so why? Methods: Sclerochronological (growth increment) and oxygen isotope profiles can be used to determine not only the time of shellfish collection to calendar date but also tide status and thereby used to reconstruct the distance of the collection point from the coast. Changes in the aquatic environment, such as sea surface temperature, salinity and water turbidity affect shell growth patterns, resulting in distinct growth lines. These consecutive growth lines are used to determine growth increments, which in turn are used to calculate calendar dates. The next step is to obtain archaeological shell samples for analysis. I have already collected modern bivalve shells (at approximately monthly intervals) along the coast of the Western Cape. Analysis of these modern shells will enable me to interpret the signatures from the archaeological samples. Modern data on sea surface temperatures along the South African coast will be factored into the interpretations. I will make use of the Archaeology thin sectioning and microscopy facilities in order to measure growth increments and determine the seasonal patterns for both the modern and archaeological mollusc samples. As they grow, shells record information about the temperature and salinity of the seawater in which the organism lived. By analyzing the O-isotope composition of a shell along the direction of growth, seasonal changes in seawater conditions can be quantified and the season of death of the animal (hence the time of collection) determined (Jones and Quitmyer, 1996; Schöne and Gillikin, 2013). Sequential samples will be removed by drilling from individual shells, to yield approx. 60 μg for analysis. The powdered shell samples will then be prepared in the Archaeology bone chemistry laboratory for isotopic analysis. The actual (mass spectrometric) measurements will be done at the Isotope Geosciences Laboratory in Nottingham. I have chosen Edinburgh University for my PhD studies because of its expertise in early prehistory (Prof. Clive Bonsall) and archaeomalacology (Dr Catriona Pickard). The School of History, Classics and Archaeology also has the thin sectioning and microscope facilities that will be essential for my seasonality and palaeoenvironmental studies of archaeological shells. Placement in a major UK university will enable me to apply (through my supervisors) to use the isotope facilities of the NERC Isotope Geosciences Laboratory for the geochemical aspects of my research. Bibliography Jerardino, A. and Marean, C. W. 2010. Shellfish gathering, marine paleoecology and modern human behavior: perspectives from cave PP13B, Pinnacle Point, South Africa. J Hum Evol 59: 412-424. Jones, D. S. and Quitmyer, I. R. 1996. Marking time with bivalve shells: Oxygen isotopes and season of annual increment formation. Palaios 11: 340-346. Marean, C. 2010. When the Sea Saved Humanity. Scientific American 55-61. Schöne, B. R. and Gillikin, D. P. 2013. Unraveling environmental histories from skeletal diaries — Advances in sclerochronology. Palaeogeography, Palaeoclimatology, Palaeoecology 373: 1-5.