1Department of Anthropology, University of New Mexico, 2Department of Anthropology, University of Tennessee
March 26, 2015 , Gateway Ballroom 2
The goal of this study is to measure the joint contributions of hierarchical and gene flow processes to patterns of regional genetic diversity. The data are from published sources and consist of 645 autosomal microsatellites genotypes from 5,418 individuals in 248 widespread populations. We use STRUCTURE and population trees to examine genetic structure and inter-regional admixture. We test the fit of the population trees to patterns of regional genetic diversity using generalized hierarchical modeling, and gauge the independent contributions of hierarchical and gene flow processes using partial Mantel tests of gene identity, hierarchical structure, and geographic distance.
We find that hierarchical processes, local exchange, and inter-regional admixture all contribute to patterns of regional diversity. Hierarchical processes play the dominant role in all regions except East Asia, where gene flow accounts for 50% of the variation compared to 30% for hierarchical structure. However, gene flow accounts for less than 35% of the variation in other regions and none of the variation in Central Asia and the Americas. The secondary role of gene flow outside of East Asia may reflect the disproportionate number of isolated foraging and horticultural populations in the sample. We also find that interregional admixture obscures hierarchical structure within regions, but that its effects are mitigated when the sources of admixture are excluded from analysis. We consider the implications of our findings for sampling strategies in studies of regional evolution, the long-standing debate about the role of clusters vs. clines in human evolution, and the non-existence of biological races.