The carbon and oxygen isotope composition of carbonate in enamel hydroxylapatite can provide information on photosynthetic pathways of plants at the base of food webs, and on hydrological conditions. Retrieval ofpalaeoenvironmental information from isotopic composition of vertebrate fossils is complicated by potential diagenetic overprinting. In this study, alteration has been assessed by examining the extent to which expected biological carbon and oxygen isotope patterns are disrupted in fossils of species whose diets can be independently predicted by other criteria. The biological patterns used are 1) the differences in carbon isotope composition between grazers and browsers, and 2) the differences in oxygen isotope composition between hippopotamus and terrestrial herbivores. Results obtained on enamel samples from Tighenif (Algeria, =700,000 yr), Melka-Kunture (Ethiopia, 0.7-1.5 myr), and Anabo Koma (Djibouti, -1.6 myr) suggest that in vivo carbon and oxygen isotope compositions are preserved in most cases. Moreover, in all three regions, modern patterns of C3 versus C4 grass dominance were present within the Pleistocene.
Bocherens et al. (1996) studied this question.