Subtle cultural boundaries reinforce genetic structure in England

Abstract

Genes and languages both contain signatures of human history. Genetics and culture have each been shown to track population movements and demographic history. Complicating this picture, cultural traits may themselves influence the ways in which people interact with one another. For example, cultural differences can produce barriers to gene flow if they cause groups of people to differentiate themselves from one another. However, the degree of cultural difference necessary and the magnitude of these effects on gene flow remain unknown. In particular, language differences may limit population mixing, and we focus on whether subtle, dialect-level linguistic differences have influenced genetic population structure, likely by affecting mating preferences. Here, we analyze spatially dense linguistic and genetic data to examine whether the intensity of differences between and within dialects in England are associated with high genetic rates of change. We find that genetic variation and dialect markers have similar spatial distributions on a country-wide scale, and become less distinct as the scale of smaller administrative units such as counties. This covariation, combined with the absence of geographic barriers that could coordinate cultural and genetic differentiation, suggests that some dialect-level linguistic boundaries have influenced the genetic population structure in England.