Isotopic biogeochemistry as a marker of Neandertal diet.

Natural abundances in 13C and 15N of bone collagen are linked to those of the diet. This isotopic signal can thus be linked to the dietary parameters of a given individual, such as the plants at the beginning of his food web and his position in the trophic web. In order to use this approach to study the diet of ancient humans, it is crucial to be sure that the original isotopic abundances of fossil collagen are preserved. This is done by controlling the biochemical purity of the organic matter extracted from fossil bones, and by checking that the isotopic differences observed in modern environments between herbivorous and carnivorous species are indeed measured in the fossil samples. Upper Pleistocene sites with a good isotopic preservation of collagen have been recognized in temperate and arctic environments. The isotopic signatures measured in such sites highlight particularities of the "mammoth steppe" fauna, and improve our knowledge of the diet of Neandertals.