Isotope study of primate tooth enamel from Sterkfontein

Aim/rationale:
We aim to reconstruct food web dynamics and the onset and evolution of early hominin meat consumption based on stable carbon, nitrogen, and oxygen isotope analyzes. Non-primate herbivore and carnivore teeth associated with hominins from Jacovec Cavern and Member 5 were sampled in December 2023 (SAHRA case ID: 21493, permit ID: 3842) and analyzed for stable isotopes in January 2024. Their stable isotope ratios serve as a “baseline” for the reconstruction of the trophic web position of the primates. Preliminary results of this dataset show a clear distinction between the stable nitrogen isotopes ratios of herbivores and carnivores. The details of these results are presented with figures in the project description accompanying this application.
For this permit we request access to destructively sample ca. 5 mg enamel of fossil teeth from primates including hominins from Sterkfontein’s Jacovec Cavern (n = 6 hominins; n = 14 non-hominin primates) and Member 5 infills (n = 6 hominins, n = 14 non-hominin primates).
This project complements the isotope dataset recently created for Sterkfontein Member 4 (Lüdecke et al., manuscript under consideration at Nature after minor revisions). The here proposed study will present the first combined measurements of stable carbon (δ13C), nitrogen (δ15N) and oxygen (δ18O) in enamel of teeth from all three hominin genera at a single South African Plio-Pleistocene locality spanning nearly 3 million years. Our proposed dataset will include δ15N measurements of the oldest hominin analyzed until now (Jacovec Australopithecus), as well as the first specimens of the taxa Paranthropus and early Homo. The resulting unprecedented stable isotope dataset will contribute significantly to our understanding of temporal and taxonomic variation in the dietary behavior of our early ancestors. We 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.
Methodology (short):
We plan to use two novel methods to produce high-precision stable isotope enamel data:
1.) the “oxidation-denitrification method,” which permits the measurement of mineral-bound organic nitrogen isotope ratios in tooth enamel, which until recently, has not been possible due to enamel’s low organic content (Leichliter et al., 2021; Lüdecke et al., 2022; Leichliter et al., 2023), and is, as of today, only possible in two labs worldwide,
2.) the “cold trap method,” which greatly reduces the sample size required for traditional measurements of inorganic carbon and oxygen isotope ratios, permitting analysis of small or valuable teeth with minimal damage (Vonhof et al., 2020).

Damage/destructive analysis
A small hole will be drilled in the tooth to extract ca. 5 mg of enamel powder, which is sufficient for combined stable carbon, oxygen, AND nitrogen analyses. Therefore, even small teeth and broken or otherwise damaged tooth fragments can be used for this project. Moreover, enamel from any part of the tooth can be used, and the least-destructive area of the tooth will be chosen for each specimen. We target teeth which form latest in life to ensure that we capture the adult diet of each individual and avoid the effect of breastmilk consumption. Project details and exemplary picture of destructively sampled teeth are reported in the attached Project Description.

Statement why this study cannot be done in South Africa:
We will perform the sampling of the fossil teeth at the ESI in Johannesburg, hence no teeth will be exported, but only the sampled 5 mg of tooth enamel powder will be taken to Germany for analysis. This is necessary, because currently only one lab in the world next to our lab in Germany can preform the nitrogen isotope analysis (i.e., the Sigman-Lab at Princeton University in the USA), therefore there is no lab in Africa who could measure nitrogen isotopes in modern or fossil tooth enamel.