Diverse bone-calcium isotope compositions in Neandertals suggest different dietary strategies.

Zooarcheological and geochemical evidence suggests Neanderthals were top predators, but their adherence to a strictly carnivorous diet has been questioned. Recent studies have demonstrated the potential of calcium-stable isotopes to evaluate trophic and ecological relationships. Here, we measure the δ44/42Ca values in bone samples from Mousterian contexts at Grotte du Bison (Marine Isotope Stage 3, Yonne, France) and Regourdou (Marine Isotope Stage 5, Dordogne, France) in two new Neanderthal individuals, associated fauna, and living local plants. We use a Bayesian mixing model to estimate the dietary composition of these Neanderthal individuals, plus a third one already analyzed. The results reveal three distinct diets: a diet including accidental or voluntary consumption of bone-based food, an intermediate diet, and a diet without consumption of bone-based food. This finding is the first demonstration of diverse subsistence strategies among Neanderthals and as such, reconciles archaeological and geochemical dietary evidence.

Isotopic calcium biogeochemistry of MIS 5 fossil vertebrate bones: application to the study of the dietary reconstruction of Regourdou 1 Neandertal fossil.

The calcium isotopic composition (δ44/42Ca) of bone and tooth enamel can be used for dietary reconstructions of extant and extinct mammals. In natural conditions, the δ44/42Ca value of bone and teeth varies according to dietary intake with a constant isotopic offset of about -0.6‰. Owing to the poor conservation of collagen, carbon (C), and nitrogen (N) isotopic compositions of the Regourdou Mousterian site (MIS 5, Dordogne, France) previously failed to provide any paleodietary information. Therefore, to reconstruct the trophic chain, we have measured calcium (Ca) isotopes from fossil bone samples of the fauna from the Regourdou site, as well as from three bone samples of the Regourdou 1 Neandertal specimen. The results show a taxon-dependent patterning of the Ca isotopic compositions: herbivores generally have higher δ44/42Ca values than carnivores. All the δ44/42Ca values of Regourdou 1 are low (<-1.6‰), placing this specimen amid carnivores. Using a bone-muscle Ca isotopic offset determined on extant animals, we further show that the δ44/42Ca value of the Regourdou 1 diet, and that of most carnivores, cannot be accounted for by the consumption of meat only, as plants and meat have indistinguishable δ44/42Ca values. Mass balance calculations indicate that the low δ44/42Ca values of the Neandertal's carnivorous diet are explained by the ingestion of bone marrow containing as little as 1% trabecular bone. Our results show that the Regourdou 1 Neanderthal consumed a mixture of various herbivorous prey, as well as trabecular bone, which probably occurred when marrow was ingested, by accident or intentionally.