My PhD in a ‘sea’shell

Determining Later Stone Age seasonal shellfish use

Understanding local climate and environmental conditions will greatly benefit our understanding of seasonal procurement strategies, resource use and occupations patterns by past populations and visa versa. Marine resources, specifically shellfish, are one such resource type known to have played a significant role in the diet of past people living along the coast. With some of the earliest and most abundant evidence of this found in shell midden sites along the southern coast of Africa dating to the Middle and Late Stone Age (c. 200-10 kyr).

My research aims to investigate the possible seasonal nature of shellfish procurement and use by LSA occupants at Pinnacle Point, situated in the Western Cape province of South Africa, through sclerochronological and oxygen isotope analysis. The basis of my research rest on the premise that molluscs preserve past en present environmental data in the structural, morphological, and chemical composition of their shells.

As with dendrochronology, sclerochronology enables one to identify internal growth increments observed through shell cross sections. These growth increments can represent tidal and/or daily to yearly growth lines. Once these growth increments have been identified via acetate peels or thin sections they can be analysed through stable oxygen isotope analysis (geochemical profiling) to ascertain what the climatic conditions (e.g. sea surface temperature) were at the time of increment formation. This data, obtained from both modern and archaeological shells of the same species, can then be plotted to create a temperature related curve. As death occurs at the time of collection of the molluscs, the geochemical profile of their last growth increments can indicate seasonal climatic trends. Hence, the seasonal nature of procurement strategies and use of shellfish by past populations.

Over the next coming months I intend to test the various sclerochronological methods on modern samples of 5 South African shellfish species (P. perna, O. sinensis, B. cincta, C. oculus and S. longicosta) before moving on to the isotopic analysis of O. sinensis and the archaeological assemblage.

For more information about me and my research interest follow my updates and progress on twitter (@Nelson-Viljoen) and Research gate.

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