Expanding the strontium isoscape for the American midcontinent: Identifying potential places of origin for Cahokian and Pre-Columbian migrants

Archaeological research has highlighted the importance of population movement and interaction in promoting cultural change and interaction in past societies. Strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) are used worldwide to track prehistoric human population movement, and recent studies have provided new insight into the role of population diversity in the pre-Columbian American midcontinent. To track such movement, we have analyzed enamel from 222 small nonmigratory terrestrial and semiaquatic fauna from a series of midcontinental geographic locations to provide initial baseline regional ⁸⁷Sr/⁸⁶Sr information. Results of this study reveal considerable overlap in the strontium isotope ranges within the midcontinent, but also identify important isotopic differences between regions. We conclude that sufficient Sr variation exists within the midcontinent to identify the movement of individuals, however, the lack of regional specificity in Sr currently limits our ability to identify specific place(s) of origin for these individuals using Sr alone. Continued isotopic research offers the potential to produce a more detailed midcontinental isoscape, which combined with other geochemical, biological, and archaeological data, allows us to refine our understanding of the movement of people in pre-Columbian America. In light of this new information, we revisited our earlier case study of Cahokian immigration, reassessing new samples (558 teeth representing 338 individuals), and confirmed that the Cahokian population included a large number of nonlocal residents.