Human migration and isolation appear to shape genetic and language diversity in opposite ways.

The finding may seem counterintuitive at first. Regions shaped by migration and population mixing often have higher genetic diversity, so it might seem logical that their languages would be more varied too. Instead, the study finds the reverse pattern.

“We were struck by how robust this inverse relationship is across the globe,” says Anna Graff, lead author of the study and linguist at the University of Zurich. “Places where people have mixed more tend to be genetically diverse, but their languages are structurally more similar. In contrast, places with long-term isolation show less genetic diversity, yet much greater diversity in how languages are structured. Crucially, this relationship holds after adjusting for a wide range of confounding factors, including deep population history such as the timing of continental settlement.”