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

Diet reconstruction in prehistoric Rapa Nui and its implications for models of resource depletion


1Anthropology Division, Idaho Museum of Natural History, 2Department of Geological Sciences, Idaho State University, 3Department of Anthropology, Idaho State University, 4Department of Anthropology, University of Hawai'i, 5Department of Biological Sciences, Idaho State University

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Previous research on Rapa Nui suggests that by AD 1650 the island experienced a dramatic reduction in available resources due to overexploitation. Various proponents argue that this reduction resulted in cultural fragmentation and decline by the time of European contact. While some archaeological and historic accounts support this model, we do not yet know the true magnitude of impact this resource shift had on the prehistoric population. We attempt to address this through the use of stable carbon and nitrogen isotopes in human tooth dentin, with the ultimate goal of identifying attendant shifts in prehistoric Rapanui diet. We initially extracted collagen from 8 samples for analysis. The mean values for δ13C and δ15N ranged between -16.67 to -19.15‰ and 12.50 to 17.05‰, respectively, with an apparent bimodal distribution (δ13C 2-tailed t-test: p=0.002; δ15N 2-tailed t-test: p<0.000) indicative of dietary differences between individuals. Comparison to published isotope values of marine and terrestrial fauna in the Pacific suggests a diet focused on terrestrial animals (chicken and possibly rat), C3 plants and near shore marine resources, with little input from higher trophic levels (e.g., pelagic fish). To evaluate this further, we analyzed 20 additional samples for δ13C and δ15N in collagen, all samples (n=28) for δ13C in bone apatite, and a sample of faunal material recovered from archaeological contexts to obtain a more accurate estimation of the Rapa Nui food web. The results of these analyses are discussed in terms of the social and physical geography of the island.

This study was supported by funding from the National Science Foundation, grant number OPP 0722771

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