Global language diversification is linked to socio-ecology and threat status

Half of the world’s ~6-7000 languages are thought to face extinction by the end of this century. Yet the historical processes of lineage diversification and loss that have generated current diversity over many millennia remain poorly understood. Here, we use Bayesian phylogenetic inference techniques to generate a supertree of extant spoken languages (n=6636) that integrates prior knowledge and uncertainty about linguistic diversification around the globe. Our posterior treeset reveals that net diversification rates are higher in regions of greater population density and landscape traversability, for languages spoken over a larger area and further from cities, and for cultures that are reliant on agriculture and maintain political links beyond the local community. We also find that evolutionary distinctness (how distantly related a language is to its closest relatives) is positively associated with language threat status, and generate a map of the world’s most evolutionarily distinct, globally endangered (EDGE) languages. Our findings provide insight into the forces shaping linguistic diversity, indicate that more of the evolutionary history of languages is at risk than expected under a random threat distribution, and reinforce the need to act now to document and protect this diversity.