Using Zooarchaeology by Mass Spectrometry and stable carbon and nitrogen isotopes to infer palaeoenvironment conditions at Grassridge Rockshelter during the Late Pleistocene and Early to mid-Holocene

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The adoption of Zooarchaeology by Mass Spectrometry (ZooMS) provides an alternative approach to traditional morphological and ancient DNA (aDNA) analysis, allowing previously unidentifiable and morphologically ambiguous remains to be identified. Dietary preferences are reflected in the stable carbon and nitrogen isotope ratios, with variations indicating behavioural, physiological, and/or environmental change. Together, fauna identified by ZooMS and stable carbon and nitrogen isotopes has the potential to provide more information about vegetation and palaeoenvironmental change than either dataset alone. This study focuses on the morphologically unidentifiable faunal assemblage from Grassridge Rockshelter (GRS), South Africa. Ten samples were selected from the late Pleistocene (LP; ca. 43–28 ka), 20 from the terminal Pleistocene (TP; ca. 13.5–11.6 ka), and 70 from the mid-Holocene (MH; ca. 7.3–6.8 ka) layers. Here, fauna identified by ZooMS and stable carbon and nitrogen isotopes from bone collagen is used to infer the palaeoenvironmental conditions at GRS during each occupation. Eighty-five percent (n = 85) of the GRS sample was successfully identified to at least tribe using ZooMS. Success increased through time, but not significantly, suggesting that ZooMS can be used on older assemblages, up to ca. 40 ka, and in warm environments. Faunal and stable isotope shifts are documented and are indicative of changing vegetation and palaeoenvironment through time. At GRS, results indicate a cool and dry grassland environment dominated by open-habitat grazers during the LP, transitioning to a warmer and mesic mosaic environment dominated by browsers during the MH. Broad taxonomic resolutions and the misidentification of a suni antelope (Neotragus moschatus) indicate a need for the development of novel ZooMS peptide markers, the expansion of the reference database, and emphasise the need to incorporate multiple proxies when undertaking palaeoenvironmental research. Furthermore, the identification of a blue duiker (Philantomba monticola) and ostrich (Struthio camelus) was unexpected, highlighting the potential of ZooMS to identify rare or unexpected taxa.
A dissertation submitted in fulfilment of the requirements for the degree of Master of Science to the Faculty of Science, University of the Witwatersrand, Johannesburg, 2022
Zooarchaeology by Mass Spectrometry, Stable carbon, Nitrogen isotopes