Indicators of Diet and Metabolism

A similarity in 5 C-values between animals and plants from the same environment was first noted by Craig (1953). Later, many field and laboratory studies have documented small shifts of l-2%c in and even smaller shifts in between an organism and its food source (DeNiro and Epstein 1978 Peterson and Fry 1987  

Archaeological studies have used the stable isotope analysis of collagen extracted from fossil bones to reconsfruct the diet of prehistoric human populations (e.g. Schwarcz et al. 1985). 

Carbon isotopes have been used successfully to explore changes in the vegetation on Earth. Ecosystems with abundant C4 biomass have been documented only from the late Neogene to the present (Cerling et al. 1993, 1997). In South Asia, isotopic records from soil carbonates and tooth enamel reveal a dramatic increase in the abundance of C4 plants at 7 1 million years ago (Quade et al. 1992 Quade and Cerling 1995 and others). 

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