Identifying locals, migrants, and captives in the Wari Heartland: A bioarchaeological and biogeochemical study of human remains from Conchopata, Peru

► Analyzed skeletons, mortuary context, and radiogenic strontium isotope ratios. ► New technique for evaluating radiogenic strontium isotope ratios ( 87Sr/ 86Sr) to detect nonlocal persons. ► 2/31 burials and 14/18 trophy heads exhibit nonlocal 87Sr/ 86Sr. ► Nonlocal trophy heads are from a variety of locales and many were highly mobile. ► Wari warriors took captives from other locales and treated them differently based on age and sex. The site of Conchopata in the central Peruvian Andes was the secondary center in the heartland of the Wari Empire (AD 600–1000), and in this study we examine whether this urban locale was populated by locals, voluntary migrants from distant regions, and/or captives who were forcibly brought to Conchopata. We examine radiogenic strontium isotope ratios from 72 dental enamel and bone samples representing 31 formal burials and 18 human trophy heads to distinguish between locals and non-locals, and we examine skeletal and archaeological data to establish whether non-local persons were voluntary migrants or captives. We also describe a new, straightforward technique in the evaluation of radiogenic strontium isotope ratios to assist in detecting non-locals when large datasets are available. Results show that natal Conchopata inhabitants should exhibit radiogenic strontium isotope ratios that range from 87Sr/ 86Sr = 0.70548 to 87Sr/ 86Sr = 0.70610. Thus, among the 31 burials, 29 exhibit local values, suggesting that Conchopata was not a cosmopolitan center to which numerous foreigners migrated; rather, it was populated by local peoples, likely the descendants of the preceding Huarpa culture. The two individuals with non-local radiogenic strontium isotope ratios are an infant and a 17–22 years old female. The archaeological context suggests that the female may have been taken captive for subsequent sacrifice, as she was interred in front of the ritual D-shaped structure in which decapitated human heads (trophy heads) and sacrificed camelids were deposited. Among the 18 trophy heads sampled, 14 have non-local values, confirming previous studies of smaller samples that suggested that Wari warriors travelled to other locales and took captives—both adults and children—for subsequent transformation into trophy heads. Additional analyses of bone-tooth pairs from a subsample (12 burials and six trophy heads) shows that the burial group was much more sedentary (homogenous radiogenic strontium isotope ratios in bones and teeth) and the troph