A dietary spectrum - Identifying omnivory and varying degrees of animal-matter consumption using paired nitrogen and zinc stable isotope

• Applicant: Dr. Nicolas Bourgon
• Subject Area: Palaeontology ; Mineralogy, Petrology and Geochemistry ; Prehistory and World Archaeology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 517968067

This project builds upon my previous works that showcased the viability of zinc isotope (66Zn/64Zn expressed as δ66Zn value) of tooth enamel in fossil food webs and outlined the presence of isotopically distinct δ66Zn values for omnivorous diets. Omnivory is a feeding strategy distinct from herbivory and carnivory and reveals a considerable complexity to organisms employing this feeding strategy and the food webs surrounding them, with various underlying rationales. The development of a method that could reliably detect such dietary behavior in the fossil record thus has important ramifications in human evolution studies, as dietary flexibility has also frequently been associated with the evolutionary success of our lineage. One of the core objectives of the proposed project is to investigate δ66Zn values of taxa with different degrees of animal- vs. plant-matter consumption to enhance the interpretative framework and discriminative power of zinc isotopes as a dietary and trophic level proxy. This goal will be achieved by employing novel applications in mass-spectrometry of zinc and oxidation-denitrification method to measure δ66Zn and δ15N values of tooth enamel from the same specimens, enabling direct comparison from a single tooth enamel sample. δ15N values are usually very sensitive to animal-based food resources because of their high protein content and bioavailability, making it an excellent tool for assessing if the low δ66Zn values (i.e., carnivorous-like) in omnivorous taxa are associated with higher δ15N values compared to those with higher δ66Zn values (i.e., herbivorous-like). Consequently, this could suggest that zinc isotopes, as a standalone proxy, can trace varying degrees of animal-matter in the diet. Specifically, the aim is to confirm that δ66Zn values can be used to trace varying degrees of animal-matter consumption, focusing on two Late Pleistocene tropical rainforest sites in Vietnam, namely Coc Muoi (148–117 ka) and Duoi U'Oi (70–60 ka) (Part 1). Then, the project will apply the combined δ66Zn-δ15N stable isotope approach to Chuifeng (1.9 Ma), an exemplary Late Pleistocene fossil collection comprising specimens of the extinct hominid Gigantopithecus blacki (Part 2). The here proposed study will serve as a high-profile proof-of-concept study by resolving the diet and trophic ecology of this enigmatic extinct great ape of Southeast Asia. The proposed project thus aims to further the interpretative framework confidence of (paleo)dietary reconstructions made with zinc isotopes to provide a tool to assess complex diets, especially for fossil hominins who likely exhibit dietary flexibility and whose evolutionary success is often associated with such dietary plasticity.

• DFG Programme: WBP Position