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


Tracking ancient animal movements in northern Tanzania using strontium isotopes

SANDI R. COPELAND1,2, DENNE N. REED3, ROBERT J. BLUMENSCHINE4, JACKSON K. NJAU5, MATT SPONHEIMER6 and MICHAEL P. RICHARDS2,7.

1Department of Anthropology, University of Colorado Denver, 2Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, 3Department of Anthropology, University of Austin at Texas, 4Department of Anthropology, Rutgers, The State University of New Jersey, 5Department of Geological Sciences, Indiana University, 6Department of Anthropology, University of Colorado Boulder, 7Department of Anthropology, University of British Colombia

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In this study we sought to determine 1) whether biologically available 87Sr/86Sr varies across northern Tanzania in the vicinity of Olduvai Gorge and Laetoli, and 2) whether fossil fauna from Olduvai Gorge potentially reflect these differences and indicate landscape movement. Strontium isotope (87Sr/86Sr) composition of tooth enamel originates from the underlying bedrock, depends on the rock’s age and original composition, and is passed into soils, plants, and animals that eat the plants in each region. In order to determine biologically available Sr isotope ratios, we measured 87Sr/86Sr from modern owl-roost rodents collected from Serengeti and Manyara National Parks in Tanzania. Results indicate that biologically available 87Sr/86Sr is higher in northern and western Serengeti National Park (~0.707-0.719) than in the eastern Serengeti plains (~0.704-0.706). This is potentially explained by differences in geology, as Precambrian bedrock underlies parts of northern and western Serengeti, while the substrate of the eastern Serengeti plains derives from recent volcanic eruptions. A pilot study of strontium isotope ratios in fossil fauna from Olduvai Upper Bed I and Lowermost Bed II shows evidence against post-depositional alteration of 87Sr/86Sr, and indicates that some bovids may have obtained their food within the local vicinity. However, a proboscidian specimen from VEK has a higher 87Sr/86Sr consistent with it having ranged in areas of northern Serengeti, western Serengeti, or elsewhere during its youth. These results suggest that strontium isotopes may prove to be a useful method for investigating land use patterns in ancient fauna and hominins from northern Tanzania.

This project was funded by the Leakey Foundation and the Max Planck Institute.

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