First enamel nitrogen isotope data of early hominins: Early Pleistocene Australopithecus (Sterkfontein Member 4, South Africa) did not consume significant amounts of animal resources

Direct evidence regarding when and to what degree our early ancestors incorporated animal resources into their diets is sparse. The strongest, but indirect, evidence for meat consumption are cutmarks on fossil bone material. Yet, meat eating has major implications for the evolution of the hominin lineage, as the consumption of this calorie-dense, high-quality food has been linked to signiܪcant adaptations (e.g., brain expan- sion) in the genus Homo. Shifting from a mainly vegetarian diet represents an encroachment of hominins into the large carnivore guild, presenting our ancestors with new competitive pressures. The understanding of animal resource consump- tion is crucial to reconstruct the timing of changes in hominin dietary behavior and to evaluate their position in (paleo)food-webs. Nitrogen isotope (Ƚ 15 N) data reveal information about an individual’s position in the food web and are frequently used in conjunction with carbon isotopes (Ƚ 13 C) to reconstruct diet. However, Ƚ 15 N has thus far only been determined in hominin specimens younger than 120,000 years because large quantities of well-preserved collagen are required. We utilize a biogeochemical method that allows us to perform Ƚ 15 N measurements of diagenetically resistant tooth enamel. We present Ƚ 15 N and Ƚ 13 C data for Australopithecus(n"7) from Sterkfontein Member 4. Our data indicates a large variation in Ƚ 15 N values between Australopithecus individuals, larger than in any other (primate) taxa analyzed from this member. The values however do not overlap with carnivore Ƚ 15 N data, pointing to a plant-based diet of these early Pleistocene hominins, providing a ܪrst glimpse into the trophic behavior of Australopithecus