Variation of bone collagen amino acid δ13c values in archaeological humans and fauna with different dietary regimes: Developing frameworks of dietary discrimination

We present bone collagen amino acid (AA) d13C values for a range of archaeological samples representing four benchmark human diet groups (high marine protein consumers, high freshwater protein consumers, terrestrial C3 consumers, and terrestrial C4 consumers), a human population with an unknown diet, and ruminants. The aim is to establish an interpretive palaeodietary framework for bone collagen AA d13C values, and to assess the extent to which AA d13C values can provide additional dietary information to bulk collagen stable isotope analysis. Results are analyzed to determine the ability of those AAs for which we have a complete set, to discriminate between the diet groups. We show that very strong statistical discrimination is obtained for all interdiet group comparisons. This is often obvious from suitably chosen bivariate plots using d113C values that have been normalized to compensate for interdiet group differences in bulk d13C values. Bi-plots of non-normalized phenylalanine and valine d13C values are useful for distinguishing aquatic diets (marine and freshwater) from terrestrial diets. Our interpretive framework uses multivariate statistics (e.g., discriminant analysis) to optimize the separation of the AA d13C values of the benchmark diet groups, and is capable of accurately assigning external samples to their expected diet groups. With a growing body of AA d13C values, this method is likely to enhance palaeodietary research by allowing the unknown diets of populations under investigation to be statistically defined relative to the well-characterized or known diets of previously investigated populations. Am J Phys Anthropol 2012. (C) 2012 Wiley Periodicals, Inc.