Hominin Paleodiets: The Contribution of Stable Isotopes

Abstract

Stable isotope ratio analysis is now regularly used to investigate early hominin diets based upon the principle that ‘you are what you eat’. Analysis of collagen from Neanderthals and anatomically modern humans prior to 20 Ka has shown them to be significantly enriched in 15N compared to contemporaneous carnivores and herbivores. This suggests that much of their dietary protein, although not necessarily their dietary energy, came from animal foods. Carbon isotope analysis of the enamel mineral of southern African australopiths and early Homo has revealed that these taxa consumed ∼30 % C4 foods such as tropical grasses, sedges, or animals that ate these foods. Moreover, the australopiths are characterized by remarkably variable δ13C values. Chimpanzees, in contrast, are nearly pure C3 consumers even in environments with abundant C4 vegetation. These data suggest that when confronted with increasingly open areas, chimpanzees continue to exploit the foods that are most abundant in forest environments, whereas southern African australopiths utilized novel C4 resources in addition to forest foods. However, new data from eastern and central Africa show that not all australopiths follow this pattern. The earliest australopiths had nearly pure C3 diets, but by about 2 Ma others ate predominantly C4 vegetation. It also appears that increased masticatory robusticity in the australopiths is associated with greater C4 consumption.