Where and when did languages emerge? The answer
In Science, a new paper by Quentin D. Atkinson "Phonemic Diversity Supports aSerial Founder Effect Model of Language Expansion from Africa" is generating a lot of well-deserved interest (see here, here, or here for instance).
Abstract: 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.