Models for Carbon Isotope Fractionation Between Diet and Bone

Dietary evaluation using isotopic analyses of carbon in collagen from bone is an exciting new area of archaeological chemistry. Analyses of bone from herbivores, carnivores, and omnivores (including humans) suggest that a simple isotopic fractionation between dietary carbon and carbon in bone collagen may be an inadequate model for interpretation of results. Dietary carbohydrates are primarily metabolized for energy and their carbon is reflected mainly in the hydroxyapatite of bone. Dietary lipids are also important energy components of the diet. Dietary proteins, on the other hand, are utilized for protein (e.g. bone collagen) synthesis as needed and only excess amino acids are metabolized for energy. Herbivores, carnivores, and omnivores thus might have different isotopic fractionation models, each of which is presented. Biochemical evidence in support of these models is discussed.