Climate conditions and dietary practices during the Second Iron Age studied through the multi-isotope analysis of bones and teeth from individuals of Thezy-Glimont, Picardie, France

The Gauls, who occupied most of Western Europe during the Second Iron Age (500 BCE-50 BCE), exploited their environment through farming and trading of local resources. The study of carbon (delta C-13), nitrogen (delta N-15), and sulfur (delta S-34) stable isotopes of 8 humans and 12 animals from the Gallic site of Thezy-Glimont, Picardie, France, provides an insight into the dietary practices of this population. Various bones from the cephalic, axial, and appendicular skeletons of three human individuals were sampled to study intra-skeletal stable isotope variability. All bones have similar collagen delta C-13, delta N-15, and delta S-34 values for each individual, showing that they followed a consistent diet during their life, and that isotopic compositions are homogeneously recorded in bones despite various turnover rates. The delta C-13 (- 20.5 parts per thousand to - 19.8 parts per thousand) and delta N-15 (+ 7.6 parts per thousand to + 9.0 parts per thousand) values indicate that the studied Gallic individuals followed a continental omnivorous diet based on C3-plants and cattle meat. High delta S-34 values, in the range + 11.7 parts per thousand to + 17.7 parts per thousand, are apparently at variance with these conclusions as they reflect a marine contribution. However, they can also be explained by a more intense regime of precipitation from the westerlies and possible contributions from the geological substratum. While deepening the knowledge of the cultural practices of Gallic tribes from Northern Gaul during the Second Iron Age, this study highlights how stable isotope compositions of body tissues can reflect the interactions between populations and their environment.