Migration, violence, and the “other”: A biogeochemical approach to identity-based violence in the Epiclassic Basin of Mexico

Bioarchaeological studies are highly successful in accessing multivalent past social identities. This study applies social identity theory to contexts of violence, developing a theoretical framework to investigate identity-based violence at the Epiclassic (600–900 CE) central Mexican shrine site of Non-Grid 4, where at least 180 individuals were ritually sacrificed and interred. Ethnohistoric and archaeological data indicate that geographic origin was a culturally significant indicator of social difference in pre-Hispanic Mesoamerica. This study therefore reconstructs the residential histories of sacrificed individuals (n = 73), analyzing radiogenic strontium (⁸⁷Sr/⁸⁶Sr) and stable oxygen (δ¹⁸O) isotopes to consider how the perception of social difference, inferred from geographic origins, contributed to the selection of victims of ritual violence. Biogeochemical results demonstrate that 70% of sampled sacrificed individuals were born and lived their early lives outside of the Basin of Mexico, migrating into the region later in life. In contrast, only 22% of individuals were born and lived in the Basin their entire lives. Observed paleomobility patterns among sacrificial victims thus suggest that they were targeted for identity-based violence based on their divergent geographic origins in the volatile socio-political landscape of the Epiclassic Basin of Mexico.