Isotopic evidence of strong reliance on animal foods and dietary heterogeneity among Early-Middle Neolithic communities of Iberia

Stable carbon and nitrogen isotope research on past populations in the Iberian Neolithic has emphasized the Atlantic and Mediterranean coasts. This study provides the first isotopic insights into the diet and subsistence economy of Early and Middle Neolithic populations from open-air sites in interior north-central Iberia. We present bone collagen carbon (δ13C) and nitrogen (δ15N) isotope ratios for 44 humans and 33 animals recovered from six cemeteries of the Ebro valley and the northern Iberian Plateau. The results obtained are consistent with the C3 terrestrial diets typical of other contemporary south-western European populations, but the spacing between human and herbivore values from Los Cascajos and Paternanbidea sites is higher than expected, and a significant positive correlation is identified between the δ13C and δ15N human values at both. Moreover, the results clearly differ from those of the Late Neolithic/Early Chalcolithic in the same region, which show significantly lower δ13C and δ15N values. These findings contribute to an understanding of the implementation of an agro-pastoral economy in interior Iberia, suggesting a stronger reliance on animal foods among the first Neolithic groups of inner Iberia than in subsequent periods as well as differential access to some resources (possibly suckling herbivores) in the diet, which may point to the existence of early social or economic inequalities that do not seem to be linked to age and sex parameters or to mortuary treatment