Human language arose only once, in southern Africa, a first-of-its-kind analysis of world languages suggests.
Verbal communication then spread across the globe as humans walked out of Africa, reaching Australia and New Zealand last.
This verbal spread parallels the dispersion of early human genes across the world, leading the researcher to conclude that language may have prompted the great human migration.
Quentin Atkinson, a psychologist at the University of Auckland in New Zealand, traced language’s origin by breaking down 504 world languages into their smallest components, called phonemes.
African languages — particularly those in the southern part of the continent — contain the greatest diversity of phonemes. As one moves away from there, the number of phonemes in each language diminishes, suggesting those languages are newer.
Tracing the spread of languages has been difficult. Most linguists use changes in words or grammatical structures to try to track language evolution. The English word “brother,” for example, translates as “bhrater” in Sanskrit, “brathir” in Old Irish, “frater” in Latin and “phrater” in Greek. These differences can be used to reconstruct the ancient words that gave rise to the modern ones. But unlike genes, these cultural units cannot be traced back far enough to distinguish patterns of language change much earlier than about 6,500 years ago.
Atkinson decided to look at units whose pedigrees might be traceable further back: phonemes, the smallest units of sound that allow us to distinguish one word from another. For example, the English words “rip” and “lip” differ by a single phoneme, one corresponding to the letter “r” and the other to the letter “l.”
Atkinson looked at the phonemes from 504 languages across the world, using as his database the authoritative online World Atlas of Language Structures, which includes phonemes based on differences in the sounds of vowels, consonants and spoken tones.
He then constructed a series of models, demonstrating first that smaller populations have lower phoneme diversity. And, as also predicted if language arose in Africa, phoneme diversity was greatest in Africa and smallest in South America and Oceania (the islands of the Pacific Ocean), the points farthest from Africa, Atkinson reported online Thursday in Science.
The pattern matches that for human genetic diversity: As a general rule, the farther one gets from Africa — widely accepted as the ancestral home of our species — the smaller the differences between individuals within a particular population.
This report was produced by Science NOW, a daily online news service of the journal Science, which can be read at sciencemag.org.