The Onset and Evolution of Early Hominin Meat Consumption (HoMeCo) - The position of Plio-Pleistocene hominins in African paleo-food webs based on nitrogen isotopes in tooth enamel

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Dietary change, specifically the incorporation of animal resources, is considered a key event in human evolution. However, direct evidence for the trophic behavior of our hominin ancestors remains elusive. The earliest signs of meat consumption include crude stone tools and possible cut marks on fossil bones (3.4 to 3.3 Ma). However, their origin and the assumption that Australopithecus shaped and used tools prior to the emergence of Homo are heavily debated.Nitrogen (N) isotopes measured in collagen from fossil bone and dentin provide key insights into the dietary behavior of species in modern ecosystems and the recent geological past (<120 kyr). However, due to diagenetic alteration, such analyses have been limited to sites with exceptional preservation. Unlike bone or dentin, organic matter in tooth enamel is protected from alteration by its highly mineralized structure, potentially preserving isotopic signals over millions of years, but low organic matter content in enamel has so far prevented N isotope analysis.Recently, my colleagues and I developed a novel oxidation-denitrification method for analyzing the isotopic composition of mineral-bound nitrogen in ~5 mg enamel, which requires over 100-fold less N compared to traditional approaches. We established that enamel N records the isotopic composition of diet and preserves a trophic signal in both a feeding experiment and in natural ecosystems. Additionally, I analyzed teeth of fossil fauna from Sterkfontein Member 4 (~2.6 to 2.2 Ma), including seven australopithecines for a pilot study. Australopithecus shows a large variation in enamel N isotope values between individuals, but does not reach carnivore values, indicating a primarily plant-based diet for this taxon. This dataset provides a first step towards better understanding the trophic behavior of early hominins.In this project, I will use enamel N isotope data to reconstruct the onset and evolution of meat consumption of Plio-Pleistocene hominins, including 14 species of Australopithecus, Kenyanthropus, Paranthropus and Homo from eastern and southern Africa. I will generate stable carbon, nitrogen, and oxygen isotope datasets for both early hominins (ca. 130 individuals) and associated fauna (herbivores, carnivores, and omnivores including non-hominin primates; ca. 2000 individuals), to assess their feeding ecology. I will target six key-localities in the East African Rift System and five cave deposits in the South African Cradle of Humankind. These sites span 4.2 to 1.4 Ma, a critical period of climate-induced environmental change and hominin (dietary) adaptation. This unprecedented N isotope dataset will contribute significantly to our understanding of regional, temporal and taxonomic variation in the dietary behavior of our early ancestors. I will evaluate the onset, evolution and importance of animal resource consumption, as well as the role of dietary flexibility in the extinction and adaptive radiation of early hominin taxa.