As human populations disperse, the separation leads to changes both in genes and in language. So if we look at human DNA and languages over time, we should find that they differ along similar geographic lines.

It’s an intuitive theory, but difficult to prove. That is, until researchers decided to match large collections of geographic, linguistic, and genetic data on hundreds of human populations worldwide.

A new study, published in Proceedings of the National Academy of Sciences, quantifies the complicated relationship between these three factors. Researchers compared the geographic presence of two things in human populations across the world: alleles (trait-defining stretches of DNA) and phonemes (the distinct units of sound that make up spoken language).

This map shows a broad picture of the geographic spread of alleles and phonemes, according to the study’s findings. The arrows show that, in most parts of the world, languages and genes occupy the same areas and even appear to have traveled along similar trajectories.

The scale of the research is impressive. “Our study directly compares the signatures of human demographic history in microsatellite polymorphisms from 246 worldwide populations and complete sets of phonemes for 2,082 languages,” the researchers write in their report. (Microsatellite polymorphisms are short DNA sequences that vary from person to person.)