Geographic insularity and intra-lifetime mobility in Late Intermediate Period (ca. 1000 – 1450 CE) Arequipa, Peru determined from 87Sr/86Sr isobiographies

Objectives

This study examines mobility adaptations to a time of sociopolitical tumult in the ancient Andes. We examine ⁸⁷Sr/⁸⁶Sr variability in human burials (n = 21) dating to the Late Intermediate Period (“LIP,” ca. 1100 – 1450 CE) in the Sihuas Valley, Arequipa, Peru. The LIP in the southern and central Peruvian Andes is characterized as a time of drought, inter-community violence, and balkanization. Grave goods reflect ties to the nearby highlands, so we examine whether any Quilcapampa burials were non-locals and characterize their intra-lifetime mobility.

Materials and Methods

We report ⁸⁷Sr/⁸⁶Sr values from tooth enamel samples (n = 35) reflecting residential origins during three distinct periods during early-life, and bone (n = 12) reflecting origins averaged over the last years of life. We use ⁸⁷Sr/⁸⁶Sr isobiographies to identify individuals who were likely non-local to Quilcapampa at some point in their lifetimes. Because there are no extreme outliers, we define the cumulative local range as mean ±2σ of archaeological human samples, extended by the range of water ⁸⁷Sr/⁸⁶Sr within 10 km. We determine the proportion of probable non-locals and compare this and intra-lifetime mobility within Quilcapampa subgroups and between neighboring sites.

Results

Two males from the northern sector exhibit non-local ⁸⁷Sr/⁸⁶Sr values, and the northern sector has a higher mean intra-lifetime ⁸⁷Sr/⁸⁶Sr range than the southern sector. Only 4.5% of burials exhibit non-local ⁸⁷Sr/⁸⁶Sr values at some point in their lifetimes—higher than contemporaneous highland sites, but low mid-elevation Arequipa valleys. Quilcapampa, however, shows a higher mean intra-lifetime ⁸⁷Sr/⁸⁶Sr range compared to neighboring mid-valley sites, possibly reflecting adaptive short-term mobility.

Conclusion

Mobility for Quilcapampa individuals was likely constrained to nearby mid-valley communities and highlands, rather than long-distance travel. Immigrants likely leveraged pre-existing intra-regional mobility networks between neighboring valleys with similar geological characteristics.

Tweetable Summary

⁸⁷Sr/⁸⁶Sr isobiographies show limited intra-lifetime mobility in LIP Sihuas Valley, Peru.