Fine-scale cultural variation reinforces genetic structure in England.

Abstract

Genes and languages both contain signatures of human evolution, population movement, and demographic history. Cultural traits like language are transmitted by interactions between people, and these traits influence how people interact. In particular, if groups of people differentiate each other based on some qualities of their cultures, and if these qualities are passed to the next generation, then this differentiation can result in barriers to gene flow. Previous work finds such barriers to gene flow between groups that speak different languages, and we explore this phenomenon further: can more subtle cultural differences also produce genetic structure in a population? We focus on whether subtle, dialect-level linguistic differences in England have influenced genetic population structure, likely by affecting mating preferences. We analyze spatially dense linguistic and genetic data-both of which independently contain spatially structured variation in England-to examine whether the cultural differences represented by variation in English phonology colocalize with higher genetic rates of change. We find that genetic variation and dialect markers have similar spatial distributions on a country-wide scale, and that throughout England, linguistic boundaries colocalize with the boundaries of genetic clusters found using fineSTRUCTURE. This gene-language covariation, in the absence of geographic barriers that could coordinate cultural and genetic differentiation, suggests that similar social forces influenced both dialect boundaries and the genetic population structure of England.