Dietary and Physiological Contributions to the Relationship between Diet, Bone Collagen, and Structural Carbonate δ13C Values

Numerous models have been proposed to explain and predict the relationship between diet, bone collagen, and structural carbonate δ13C values. Within these models, many internal and external factors are implicated in generating the observed variation in δ13C values, such as trophic level, dietary protein source, digestive physiology, tissue growth and remodeling, and post-mortem chemical alteration of bone collagen and bone mineral. The current understanding of the relationship between the isotopic chemistry of bone and diet hinges on the observation that bone collagen and structural carbonate fractionate differentially from diet due to underlying metabolic differences. The stable carbon isotopic composition of bone collagen is shown to strongly reflect the isotopic composition of dietary protein. In contrast, the stable carbon isotopic composition of structural carbonate within bone mineral is representative of the isotopic composition of total diet. The spacing between the δ13C values of bone collagen and structural carbonate is often used as a measure for understanding variation in the isotopic composition of dietary protein relative to total diet. However, the complexity of the diet-tissue relationship often provides limitations and challenges to paleodietary reconstruction using stable isotopic analysis. This paper explores some of the dietary and physiological factors producing and affecting the relationship between diet, bone collagen, and structural carbonate δ13C values