Effect of Diet Quality and Composition on the Isotopic Composition of Respiratory CO₂, Bone Collagen, Bioapatite, and Soft Tissues

Abstract

The isotopic ratios of common light elements often provide useful information about past geologic, environmental, or biologic history. Bender’s (1968) clear identification of two distinct isotopic values for carbon from C₃ and C₄ plant organic matter led to the experiments which showed that animal δ¹³C values were closely related to dietary values (DeNiro and Epstein 1978a; Tieszen et al. 1983). Results from field applications (DeNiro and Epstein 1978b; Vogel 1978; Tieszen et al. 1979; Tieszen and Imbamba 1980) established the usefulness of these tracers and soon led to numerous archaeological studies. C and N, both present in bone collagen, have been most useful to suggest marine versus terrestrial dependence, to establish maize utilization or dependence on legumes, and to identify relative trophic-level positions or carnivory versus herbivory. Recently, attention has been focused on the use of bioapatite CO₃ (Lee-Thorp et al. 1989a, 1989b; Lee-Thorp and van der Merwe 1991) as a supplement to collagen, especially in bones older than 10000 years, and as an adjunct to collagen for estimates of carnivory. The ¹⁸0 signal in bioapatite also has the potential to provide information on the water status of the individual or the environment. Sulfur isotopes δ³⁴ S), when present in sufficient quantities, as in hair or skin, are also useful and in some cases can distinguish clearly between marine and terrestrial dietary sources (Krouse and Herbert 1988).