An inverse correlation between linguistic and genetic diversity
Human population history, as traced by our genome, has shaped the distribution of languages around the world. While case studies suggest that population history can also affect specific structures of languages, such as patterns in their sound systems and grammars, results are conflicting, and it remains unknown whether such effects hold globally. Here we show that, adjusting for geography, phylogeny, and environment, genetic diversity is inversely correlated with diversity in linguistic structures. Low genetic diversity (i.e. excess homozygosity) results from relative isolation, and this promotes diversification in language. High genetic diversity results from contact and migration, and this promotes homogenization in language. These effects are particularly pronounced in Asia and, under some conditions, also in a few other areas, suggesting sociocultural factors contributing to differences in how strongly isolation favors linguistic diversity and how strongly contact promotes linguistic homogenization. Our results suggest that present-day hotspots of linguistic diversity, which are characterized by relative isolation, may provide a privileged window on the dynamics of linguistic evolution as they are less affected by the vast demographic expansions, migrations, and extinctions that characterize the Neolithic age.