Stable Carbon- and Nitrogen-Isotope Ratios of Bone Collagen Used to Study Coral-Reef and Terrestrial Components of Prehistoric Bahamian Diet

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Abstract
Previous studies have demonstrated that stable carbon- and nitrogen-isotope ratios of bone collagen can be used to distinguish marine and terrestrial components of prehistoric human diet. However, when this method was first applied to prehistoric Bahamians, their bone-collagen nitrogen-isotope ratios were found to be outside the ranges observed for other coastal populations that ate substantial quantities of marine foods. This study examines in detail the distributions of stable carbon and nitrogen isotopes in Bahamian food chains. Our results indicate that the unique isotopic signature in bone collagen of prehistoric Bahamians reflects the enrichment of 13C and the depletion of 15N in seagrass and coral-reef communities relative to other oceanic environments. The results also demonstrate that bone-collagen 13C/12C ratios can be used to distinguish marine from terrestrial contributions in the prehistoric Lucayan Taino diet, and that 15N/14N ratios serve to identify the use of certain marine food groups. This approach should prove useful for the study of consumption practices in other tropical coral-reef environments and as a method for evaluating theoretically predicted optimal diets.