The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)


Strontium isotope ratios of mammalian fossils from Malapa, South Africa

DARRYL J. DE RUITER1,2, MATT SPONHEIMER3, SANDI COPELAND4, JULIA A. LEE-THORP5,6, LEE R. BERGER2 and PETRUS LEROUX6.

1Department of Anthropology, Texas A&M University, 2Institute for Human Evolution, University of the Witwatersrand, 3Department of Anthropology, University of Colorado Boulder, 4Department of Anthropology, University of Colorado Denver, 5Research Laboratory for Archaeology and the History of Art, Oxford, 6AEON EarthLAB, Geological Sciences, University of Cape Town

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Strontium isotope (87Sr/86Sr) ratio data have recently been used to investigate ranging and residence patterns among early hominins in South Africa (Copeland et al., 2011, Nature 474: 76). The 87Sr/86Sr ratios recorded in mammalian teeth reflect the 87Sr/86Sr ratios of the geological substrates on which individuals live, thus they are proxies for landscape usage patterns in hominins and other mammals. In the present study we provide 87Sr/86Sr ratio data for a sample of fossil rodents, lagomorphs, bovids, and a single adult female of Australopithecus sediba (MH2) from the site of Malapa, South Africa. The 87Sr/86Sr ratios of these teeth were measured using laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS), a minimally destructive sampling technique. The rodents and lagomorphs reveal 87Sr/86Sr ratios indistinguishable from the dolomites housing the fossiliferous caves, suggesting that they lived and died on the dolomites, which is consistent with the small home ranges of these micromammals. The larger bovids, on the other hand, appear to be non-local, thus they spent at least some portion of their lives on a substrate other than the dolomites where they died and were deposited. Sampling of a small chip of enamel from the M2 of MH2 reveals a 87Sr/86Sr ratio just outside the maximum value recorded for the local dolomites. This suggests that this individual had either ranged beyond the dolomites during her juvenile years, or that she had dispersed from a remote geological substrate to the local dolomites where she was ultimately buried, possibly upon reaching reproductive maturity.

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