Seminar of Tina Ludecke

Abstract:

Stable nitrogen isotope analysis (δ15N) is a crucial method for examining dietary patterns and trophic interactions in both modern and ancient ecosystems. Although δ15N is commonly measured in collagen or soft tissues, its use in paleontological research has been constrained by the diagenetic degradation of organic material, typically limiting studies to well-preserved specimens less than several tens of thousands of years old. Tooth enamel, the densest mammalian tissue, offers exceptional preservation potential, but its low organic content has historically impeded δ15N analysis.
We now measure δ15N in mineral-bound organic matter in tooth enamel (δ15Nenamel), overcoming this limitation and enabling isotopic analysis of fossils far older than previously possible (i.e. millions of years) with minimal sample material (~5 mg). This development expands the isotopic toolbox for investigating ancient ecosystems and evolutionary trajectories.
Our studies demonstrates that δ15Nenamel reliably reflects trophic-level enrichment, with a 3–4‰ increase per trophic step in the food-web, comparable to δ15N from collagen, as shown with analyses of controlled feeding experiments and modern mammals that lived in natural habitats.
Furthermore, isotopic data from Pliocene Sterkfontein Member 4 (South Africa) provide the first δ15Nenamelmeasurements for Australopithecus and coexisting fauna. Our findings reveal a variable but predominantly plant-based diet (largely C3) for these early hominins. These results provide crucial insights into the ecological role of Australopithecus, emphasizing their reliance on plant- based diets.
The ability to measure δ15Nenamel represents a transformative advancement for paleoecological research, offering a powerful tool to investigate the diets and adaptations of extinct species across deep time.