⁸⁷Sr/⁸⁶Sr data indicate human post-juvenile residence mobility decreases over time-elapsed since initial Holocene island colonization in the Pacific and Caribbean

During the Holocene colonization of islands in the Pacific and Caribbean by agropastoral and horticulturalist communities, a variety of proxies (material, genetic, zoogeographic etc.) indicate substantial inter-island and inter-community contact. It has been suggested that this contact represents an adaptive response to mitigate intrinsic demographic fragility during the initial phases of island colonization, and that this exogamous imperative faded in the aftermath of initial dispersal as overall population density increased. Here, we evaluate this model by synthesizing and comparing increasingly available ⁸⁷Sr/⁸⁶Sr data from funerary populations in the Pacific and Caribbean. After performing basic hygienic discrimination, we conclude that the Caribbean data—both from across the region, and on an intra-site/island basis—lend support to this model, with high early in-migration succeeded by comparatively low in-migration in a relationship which, based on chi-square tests, is statistically significant (1, N = 290) = 4.046, p = 0.044). The Pacific situation is more complex, with data from the Bismarck Archipelago and northern Solomon Islands skewing the analysis. However, in considering these data in detail, we demonstrate that there are reasons to suppose that the Pacific data may also tentatively support a model of high rates of in-migration being replaced later in settlement histories by comparatively low rates. We conclude by highlighting future directions for this incipient research program.