Nitrogen isotopic composition of tooth enamel organic matter records trophic position in modern and fossil ecosystems

Abstract Nitrogen isotopes are widely used to study the trophic position of animals in modern food webs, however, their application in the fossil record is severely limited by degradation of organic material during fossilization. In this study, we show that the nitrogen isotopic composition of organic matter preserved in mammalian tooth enamel (δ15Nenamel) records diet and trophic position in modern and fossil ecosystems. The δ15Nenamel of modern African mammals shows a trophic enrichment of 3.7 ‰ between herbivores and carnivores, as well as a strong positive correlation between δ15Nenamel and δ15Nbone-collagen values from the same individuals. δ15Nenamel values of Late Pleistocene fossil teeth record expected dietary patterns, despite complete diagenetic loss of collagen in the same specimens. We demonstrate that δ15Nenamel represents a powerful new paleodietary proxy that could help delineate major dietary transitions in ancient vertebrate lineages, such as the onset and intensification of animal resource use in early hominins.