Carbon and nitrogen stable isotopes reveal the human paleodiet evolution during the 8th-12th century in the Venetian Lagoon (Italy)

The paleodiet evolution in a human community of Venetian Lagoon between the eighth and twelfth centuries has been reconstructed by the stable isotopes analysis of delta C-13 and delta N-15 found in collagen of teeth and bones from St. Mauro archaeological site (Jesolo, Venice). A total of 52 individuals of various ages, sex, chronologies, and pathological condition were included in this study. Our findings revealed the presence of two distinct dietary patterns influenced only by chronology. We observed that a more fish-based diet (30-60% of the overall diet) prevailed between the eighth and tenth centuries. However, between the tenth and twelfth centuries, fish consumption decreased (10-30% of the overall diet), and there was a shift towards a diet rich in terrestrial protein sources. We link this change in dietary habits to economic development also evidenced by the transformations of the site and increased trade with the hinterland. Furthermore, it was observed significantly higher delta N-15 values in individuals from 8th-10th compared to those from tenth-twelfth centuries. We proposed two potential explanations: a shift in child-rearing practices, such as delayed weaning during early middle age compared to late middle age, or a change in diet of breast feeders.