Some 7,500 languages are spoken or signed around the world today. Though that might sound like a lot, the number could have been up to 10 times higher a few thousand years ago, researchers report July 23 in Science.
“That was the golden age of linguistic diversity,” says Claire Bowern, a linguist at Yale University.
The finding comes as scientists are racing to document, or ideally preserve, languages nearing extinction. Half of today’s languages are now endangered, and roughly four languages disappear every year.
Linguists and cognitive scientists have long sought to identify features of language, whether unique to a given culture or universal, to generate theories about how humans reason about the world. Any underestimate of linguistic diversity would mean those theories are missing a lot of what is possible.
But ancient languages are challenging to study. They don’t leave a fossil record. And writing emerged relatively recently — in the past 6,000 years — and among only a subset of languages. So Bowern’s team developed a model to try to quantify what might have happened to language diversity over the past several thousand years, including pinning down when it started to shrink.
The team first looked at more than 170 contemporary hunting and gathering groups worldwide as a proxy for past populations. Though such groups have changed across time, many key aspects of their social structure have remained stable, research elsewhere suggests. Chiefly, foraging groups vary in size but typically include several hundred people to more than a thousand. And, broadly speaking, each group speaks a single language.
That 1–1 ratio of languages to foraging groups likely dominated before farming emerged some 12,000 years ago, the team concluded. With a global population of 4.4 million to 7 million people at that time, the total number of languages then was probably between 4,500 and 6,200.
This gave the team both a starting point for the model and an ending point, based on present day numbers. “At the start of our modeling 12,000 years ago, we have roughly 5,000 languages to 6 million people. At the end point, we have 7,500 languages for 8 billion people,” Bowern says.
The puzzle became what happened in between. The pivot to agriculture would have changed quite a lot. Abundant food enabled population sizes to balloon, as well as the number of people speaking any given language. Though language diversity would increase, it wouldn’t keep pace with population growth, Bowern says. Assume that a growing population speaking the same language split into two. Based on what’s known about language evolution, it would take 500 to 1,000 years for their languages to become distinct.
So the team simulated multiple scenarios that included the known data points and existing assumptions, such as varying population estimates based on the existence or absence of disease. Under every scenario, language diversity peaked at between 20,000 and 75,000 languages some 1,000 to 3,000 years ago. Then that diversity rapidly dropped off. The timing suggests that agricultural intensification and the rise of nation-states, such as the Roman and Greek empires, led to catastrophic language loss.
Bowern’s team now hopes to zoom in to understand how linguistic diversity changes over time on a regional scale.
The finding is likely to inform, but not settle, ongoing debates over the landscape of languages across time. It goes against a popular theory that puts linguistic diversity at its highest before the dawn of agriculture, some 12,000 years ago, as well as another theory that pegs today’s language extinction crisis to the rise of colonialism just 500 years ago.
It opens a new perspective, says Chiara Barbieri, a geneticist studying language diversity at the University of Cagliari in Sardinia, Italy, who finds the idea that so many languages may have been lost to time mind-boggling. There is tremendous variation even among the remaining languages today, from the absence or presence of gendered nouns, articles, clicks to communicate or tones that convey meaning nonnative speakers can’t even hear. “Are there people who developed languages with some traits that we can barely imagine now?” she wonders. “It makes your head spin.”
