Zinc isotope ratios of bones and teeth as new dietary indicators: results from a modern food web (Koobi Fora, Kenya).

Michael P. Richards,Klervia Jaouen,Jean-Jacques Hublin,Margaret Schoeninger,Melanie Beasley

doi:10.1038/srep26281

Abstract

In order to explore the possibilities of using zinc (Zn) stable isotope ratios as dietary indicators, we report here on the measurements of the ratio of stable isotopes of zinc (66Zn/64Zn, expressed here as δ66Zn) in bioapatite (bone and dental enamel) of animals from a modern food web in the Koobi Fora region of the Turkana Basin in Kenya. We demonstrate that δ66Zn values in both bone and enamel allow a clear distinction between carnivores and herbivores from this food web. Differences were also observed between browsers and grazers as well as between carnivores that consumed bone (i.e. hyenas) compared to those that largely consume flesh (i.e. lions). We conclude that Zn isotope ratio measurements of bone and teeth are a new and promising dietary indicator.

Highlights

In order to explore the possibilities of using zinc (Zn) stable isotope ratios as dietary indicators, we report here on the measurements of the ratio of stable isotopes of zinc (66Zn/64Zn, expressed here as δ66Zn) in bioapatite of animals from a modern food web in the Koobi Fora region of the Turkana Basin in Kenya
Preliminary studies demonstrated that the isotopic compositions of these non-traditional elements in animal tissues were related to their diets[1,2,3,4,5,6,7,8,9], and in human blood Zn isotope values could be used to detect meat-consumption[10,11]
Zn stable isotope values for plants and herbivores from Koobi Fora result in different distributions of values from those observed for the South African sites (Kruskal Wallis test, Table S4)

Summary

Introduction

In order to explore the possibilities of using zinc (Zn) stable isotope ratios as dietary indicators, we report here on the measurements of the ratio of stable isotopes of zinc (66Zn/64Zn, expressed here as δ66Zn) in bioapatite (bone and dental enamel) of animals from a modern food web in the Koobi Fora region of the Turkana Basin in Kenya. A 66Zn-enrichment relative to 64Zn apparently occurs in body tissues during Zn intestinal absorption from plants, which has been attributed to the precipitation of dietary Zn with phytates in the intestine, inhibiting Zn absorption, and favoring the binding of Zn light isotopes[3,13,19] Due to this fractionation during intestinal absorption, the Zn isotopic ratios of herbivore body tissues should be higher than the Zn isotope values of their diets[3,13]. Carnivores, which do not consume phytates (which are associated with Zn), should have less of a fractionation between food Zn isotope ratios and their body tissue Zn isotope values These predictions are consistent with two studies www.nature.com/scientificreports/

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Conclusion