Human genetic and phenotypic diversity declines with distance from Africa, as predicted by a serial founder effect in which successive population bottlenecks during range expansion progressively reduce diversity, underpinning support for an African origin of modern humans. Recent work suggests that a similar founder effect may operate on human culture and language. Here I show that the number of phonemes used in a global sample of 504 languages is also clinal and fits a serial founder–effect model of expansion from an inferred origin in Africa. This result, which is not explained by more recent demographic history, local language diversity, or statistical non-independence within language families, points to parallel mechanisms shaping genetic and linguistic diversity and supports an African origin of modern human languages.
Language locations and regional variation in phonemic diversity. (A) Map showing the location of the 504 sampled languages for which phoneme data was compiled from the WALS database. (B) Box plots of overall phonemic diversity by region reveal substantial regional variation, with the highest diversity in Africa and the lowest diversity in Oceania and South America. The same regional pattern also applies at the language family level.