Isolated human groups speak more diverse languages

A surprising global pattern

At first glance, the findings seem surprising. One might expect regions with greater genetic diversity, often shaped by migration and population mixing, to also show greater diversity in language. But the study reveals the opposite.

“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.”

Linking genes and language

To uncover this pattern, the researchers combined large-scale genetic and linguistic datasets, analysing how genetic variation across individuals relates to structural variation across languages within each region. Importantly, they controlled for other possible influences like geographic proximity, population density and environmental factors, allowing to isolate the role of demographic history.

Contact, migration and isolation are formative forces

The result is a clear global signal: the same forces that shape the genetics of human populations – contact, migration and isolation – also shape the diversity of language structures, but in opposite ways. “The key insight is that contact and isolation have opposite effects on genes and languages”, explains Chiara Barbieri, senior author and population geneticist at the University of Cagliari. “Contact increases genetic diversity, but it also promotes the spread of linguistic features, making languages more similar. Isolation, by contrast, limits genetic diversity while allowing languages to evolve independently.”[ba1] [AG2] [AG3] [BB4] 

Genetically isolated regions are hotspots of linguistic diversity

This dynamic helps explain why some regions of the world stand out as hotspots of linguistic diversity. Areas such as New Guinea or the Himalayas are relatively isolated genetically; at the same time their languages are hotspots of diversity. “Such hotspots give us a glimpse of what languages can do when evolving under conditions of relative isolation”, says Balthasar Bickel, senior author and Director of the Institute for the Interdisciplinary Study of Language Evolution at the University of Zurich. “They preserve a wider range of ways of organizing grammar, sound and meaning, a range that cannot be observed elsewhere because it got reduced by long histories of contact.”

Beyond documenting a striking global pattern, the study highlights a broader implication: linguistic diversity is deeply intertwined with human history. “What might initially look like a paradox turns out to be a simple and actually intuitive principle”, Graff concludes. “The same processes that keep populations apart allow languages to grow apart as well.”

Reference
Anna Graff, Erik J. Ringen, Taras Zakharko, Mark Stoneking, Kentaro K. Shimizu, Balthasar Bickel, Chiara Barbieri. 2026. An inverse correlation between structural linguistic and human genetic diversity. PNAS. DOI: 10.1073/pnas.2526762123

More information
NCCR Evolving Language: https://evolvinglanguage.ch 

Contacts:
Anna Graff
Institute for the Interdisciplinary Study of Language Evolution
University of Zurich

anna.graff@uzh.ch
+41 78 765 96 86

Prof. Chiara Barbieri
University of Cagliari

chiara.barbieri@unica.it
+39 329 007 6779

Prof. Balthasar Bickel
Director of the NCCR Evolving Language, and Institute for the Interdisciplinary Study of Language Evolution
University of Zurich

balthasar.bickel@uzh.ch

+41 77 445 67 75