Sex-linked genetic diversity originates from persistent sociocultural processes at microgeographic scales.

Ning Ning Chung,Herawati Sudoyo,J Stephen Lansing,Safarina G Malik,Guy S Jacobs,Lock Yue Chew,Murray P Cox

doi:10.1098/rsos.190733

Abstract

Population genetics has been successful at identifying the relationships between human groups and their interconnected histories. However, the link between genetic demography inferred at large scales and the individual human behaviours that ultimately generate that demography is not always clear. While anthropological and historical context are routinely presented as adjuncts in population genetic studies to help describe the past, determining how underlying patterns of human sociocultural behaviour impact genetics still remains challenging. Here, we analyse patterns of genetic variation in village-scale samples from two islands in eastern Indonesia, patrilocal Sumba and a matrilocal region of Timor. Adopting a ‘process modelling’ approach, we iteratively explore combinations of structurally different models as a thinking tool. We find interconnected socio-genetic interactions involving sex-biased migration, lineage-focused founder effects, and on Sumba, heritable social dominance. Strikingly, founder ideology, a cultural model derived from anthropological and archaeological studies at larger regional scales, has both its origins and impact at the scale of villages. Process modelling lets us explore these complex interactions, first by circumventing the complexity of formal inference when studying large datasets with many interacting parts, and then by explicitly testing complex anthropological hypotheses about sociocultural behaviour from a more familiar population genetic standpoint.

Highlights

Over the last decade, genetics has transformed our knowledge of the last great human migration into pristine environments—the settlement of the greater Pacific region [1,2]
We study mitochondrial DNA (mtDNA) and the Y chromosome in two matched sets of communities: 14 patrilocal villages on Sumba, where newly-wed couples move to the community of the husband, and nine matrilocal villages on Timor, where newly-wed couples move to the community of the wife
The axes show the level of haplotype diversity observed on the mtDNA, inherited from the mother, and on the Y chromosome, inherited from the father

Summary

Introduction

Genetics has transformed our knowledge of the last great human migration into pristine environments—the settlement of the greater Pacific region [1,2]. Recent work is providing increasingly precise descriptions of the genetic impact of kinship practices [24], as well as the genetic relationships between communities at fine geographical scales [25], while advances in modelling are revealing both the drivers of changes in kinship practices at global scales [26,27] and surprising diversity in the rate and manner of change more locally [28] Despite these advances, discussion of social processes impacting genetic diversity commonly focuses on the proximate genetic cause— sex-biased migration—with little emphasis on the sociocultural processes driving this behaviour. What is less clear is how these patterns arise at very small geographical scales, and how the details of local social behaviour cascade up to more observed global genetic patterns

Methods

Results

Conclusion