Over 6 years, we documented Zn isotope variations in more than 180 animal species and 70 plant species, enhancing our understanding of how local environment, metabolism, and diet influence these ratios. Our research demonstrated the potential of δ66Zn to track the onset of frequent aquatic food consumption in human evolution, as well as other dietary habits.
Key findings include distinct differences between invertebrates and vertebrates, as well as between animals that consume whole prey and those that tear it apart. Thanks to P. Mejean’s work, we identified higher δ66Zn values in cereals and legumes compared to other plants, reinforcing the utility of δ66Zn in tracing the adoption of agriculture. Notably, Z. Moubtahij’s research on an Iberomaurusian population at the end of the Pleistocene revealed a diet rich in plants. She also demonstrated the absence of fish consumption among coastal Neolithic populations in North Morocco, similarly to earlier hunter-gatherers, thus showing a distinct pattern compared to Europe.
We published the first δ66Zn values for Pleistocene Neandertals and modern humans across four studies, showcasing the potential of Zn isotopes as dietary tracers, particularly in regions where traditional trophic proxies are not viable. Additionally, J. M. Cardoso’s research challenged the classic trophic level model by showing that, in Brazilian tropical food webs, carnivores do not follow the expected pattern of feeding on mammals. Another major discovery was the identification of Zn isotope ratios as a proxy for breastfeeding.
Collaborative controlled feeding experiments provided further insights into Zn isotope fractionation in vertebrates, demonstrating that:1) Zn isotope ratios in body tissues directly reflect the δ66Zn of consumed animal foods. 2) Fractionation patterns within mammalian and fish tissues are comparable.
We also documented seasonal variations in δ66Zn values in terrestrial mammal tissues. One particularly striking application of our research was the combined use of Zn and O isotope ratios in horse teeth, which revealed that modern humans reached high European latitudes during a cold episode of the Pleistocene—challenging previous assumptions.
By integrating δ66Zn with other isotope proxies and Bayesian mixing models, we reconstructed the diverse diets of precolonial populations in Brazil, including their consumption of shellfish. This contributed to the longstanding debate on whether the shells used to build sambaquis also played a significant role in the diet of these populations. Another innovative development was the use of machine learning to construct an isoscape addressing inconsistencies in sulfur isotope ratios in Europe. This led to the creation of triple Sr-O-S isoscapes, which have since become a key tool for determining individual geographic provenance.
Our research on freshwater seals, along with studies on dolphins and other marine mammals, clarified the relationship between trophic level and diet. The work of G. Le Bras, combining Zn isotope analysis with CSIA-AA and research from the BAP led by A. Weber, confirmed distinct δ66Zn values between prehistoric consumers of game fish and those consuming both game fish and seals.
We also addressed key analytical challenges to enable less destructive analyses while preserving valuable samples. Key achievements included:1)The use of a micromill to sample small teeth.2)The development of a protocol allowing the combined analysis of Ca, Sr, and Zn stable isotopes from a single sample.
Additionally, B. Fuller and C. Lagane established CSIA-AA analysis at GET, making our lab the fifth worldwide—and the first in France—to develop this approach for archaeology. We fostered new collaborations, particularly with genomic experts and specialists working on Neandertal and modern human samples from tropical and arid regions.
Zn isotope ratios are now recognized as a key tool for reconstructing ancient diets, especially in terrestrial contexts where protein preservation is limited. Many insights from the past 6 years continue to shape the field, with numerous publications forthcoming. Notably, our long-term collaboration with R. Colleter contributed to a study tracing dietary inequality related to gender over 10,000 years in Europe.
The results of this research have been published in 27 articles, 2 PhD dissertations, 23 conference presentations, and 3 posters, with 10 additional publications currently under review or in preparation. Our findings have also been disseminated through radio interviews and public outreach articles.
