Unlike archaeological radiocarbon dating based on the fixed rate of decay of the carbon-14 isotope, there is simply no fixed rate of decay of basic vocabulary, which would allow us to date ancestral proto-languages.

BBC: English language 'originated in Turkey'

But the latest Science paper "and our own observations suggest that it is possible to detect an arrow of time" underlying proto-human languages spoken more than 8, 000 years ago, said Murray Gell-Mann of the Santa Fe Institute in New Mexico, who read the Science paper and supports it.

WSJ: Study Points to a Single, Original Language for All Humans