Abstract
Language is a key adaptation of our species, yet we do not know when it evolved. Here, we use data on language phonemic diversity to estimate a minimum date for the origin of language. We take advantage of the fact that phonemic diversity evolves slowly and use it as a clock to calculate how long the oldest African languages would have to have been around in order to accumulate the number of phonemes they possess today. We use a natural experiment, the colonization of Southeast Asia and Andaman Islands, to estimate the rate at which phonemic diversity increases through time. Using this rate, we estimate that present-day languages date back to the Middle Stone Age in Africa. Our analysis is consistent with the archaeological evidence suggesting that complex human behavior evolved during the Middle Stone Age in Africa, and does not support the view that language is a recent adaptation that has sparked the dispersal of humans out of Africa. While some of our assumptions require testing and our results rely at present on a single case-study, our analysis constitutes the first estimate of when language evolved that is directly based on linguistic data.
Highlights
A capacity for language is a hallmark of our species [1,2], yet we know little about the timing of its appearance
We have considered the possibility that we are overestimating the phonemic diversity of African languages by restricting our sample to click languages
Spoken in Thailand, Malaysia, and Myanmar, as the colonizers of the Andaman Islands could have departed from one of these regions. By relaxing this assumption and including in our sample all the Mainland Southeast Asian languages contained in UCLA Phonological Segment Inventory Database (UPSID), we find that the average phonemic diversity in the region, PB, is 40:21+2:17, which increases our estimate to 242–168 kya and 236–163 kya for linear and exponential growth, respectively
Summary
A capacity for language is a hallmark of our species [1,2], yet we know little about the timing of its appearance. We do not know whether these archaic hominins produced speech, and if so, to which extent it was similar to our capacity for language. The anatomical and genetic data lack the resolution necessary to differentiate proto-language from modern human language. Until this resolution is improved, we need alternative lines of evidence in order to better understand the timing of language origin
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