Food and diet of the pre-Columbian mound builders of the Patos Lagoon region in southern Brazil with stable isotope analysis

A constant and intense debate in South American archaeology stands on the origin and patterns of food production of ancient populations and the correlation of both aspects with demographic growth and social complexity. Some studies associated population growth with the shift from foraging to agricultural practices in hotspots on the continent. This association has been confronted by a number of studies performed in recent years that reconstructed dietary patterns for several tropical and subtropical areas of eastern South America. However, there is still a lack of information on the diet for Late Holocene populations in the wetlands of the Pampa Biome. In order to access the paleodiet of earthen-mound builders from southern Patos Lagoon (Brazil), this study combined bulk collagen stable carbon and nitrogen isotopes analysis of faunal and human remains with Bayesian Stable Isotope Mixing Models. The paleodiet of 20 human and one dog remains from six sites was reconstructed. The Bayesian mixing model on collagen δ13C and δ15N values revealed variable subsistence strategies with high consumption of marine/estuarine protein for some individuals. Other individuals’ diets relied on terrestrial/freshwater resources as protein sources. In southeastern South America, such patterns reinforce the resource-rich aquatic environment as a facilitator for the endurance of mixed economies. In addition, our results suggest that the Patos Lagoon surroundings was a “hub of interactivity” characterised by a remarkable intra-site dietary variability.