Demographic structure, diet and migration in the southern Andes: new analyses of the site Osario Potrero Las Colonias, Uspallata (Mendoza, Argentina)

Palaeodemographic and isotopic analyses provide key information for understanding the composition and social dynamics of past human groups and within-population variation in diet and geographic range. The objectives of this study are to reconstruct the demographic structure of the Osario Potrero Las Colonias site, to strengthen its chronology and, by means of stable (delta C-13(col)., delta C-13(ap)., delta N-15) and strontium (Sr-87/Sr-86) isotopes, to assess the dietary composition and geographic place of residence of a random sample of individuals from the site. This is a multiple archaeological burial with radiocarbon dates between AD 1320 and 1450, which places it in a period of important changes in regional history, related to a demographic increase and the arrival of the Inka empire on its southern frontier (ca. AD 1400). The demographic composition of the site reveals a broad social group unique in the region due to the large number of individuals bur- ied, especially young children. Strontium isotopes indicate that the sampled individuals did not reside in Uspallata during the last years of their lives, and hence can be considered migrants, while stable isotopes indicate a predominant consumption of C-4 resources.