Today, some 7,500 languages are spoken or signed around the world. Although this may seem like a lot, the number could have reached 10 times higher a few thousand years ago, researchers report July 23 Science.
“It was the golden age of linguistic diversity,” says Claire Bowern, a linguist at Yale University.
The discovery comes as scientists work to document, or ideally preserve, languages facing extinction. Half of today’s languages are now threatened and around four languages disappear each year.
Linguists and cognitive scientists have long sought to identify the characteristics of language, whether they are unique to a given culture or universal, to generate theories about how humans reason about the world. Any underestimation of linguistic diversity would mean that these theories miss much of what is possible.
But ancient languages are difficult to study. They do not leave fossil traces. And writing appeared relatively recently – within the last 6,000 years – and among only a subset of languages. So Bowern’s team developed a model to try to quantify what may have happened to linguistic diversity over the last few thousand years, including determining when it began to decline.
The team first looked at more than 170 contemporary hunter and gatherer groups around the world as an indicator of past populations. Although these groups have changed over time, many key aspects of their social structure have remained stable, research elsewhere suggests. Primarily, foraging groups vary in size but typically include several hundred individuals to over a thousand. And generally speaking, each group speaks only one language.
This 1-to-1 ratio of languages to foraging groups likely dominated before the emergence of agriculture around 12,000 years ago, the team concluded. With a world population of 4.4 to 7 million at that time, the total number of languages was then probably between 4,500 and 6,200.
This gave the team both a starting point for the model and an end point, based on current numbers. “At the start of our modeling, 12,000 years ago, we had about 5,000 languages for 6 million people. At the end point, we have 7,500 languages for 8 billion people,” says Bowern.
The puzzle became what happened between the two. THE turn to agriculture would have changed a lot. Abundant food allowed population size to increase, as well as the number of people speaking a given language. Although linguistic diversity would increase, it would not keep pace with population growth, Bowern says. Suppose a growing population speaking the same language splits into two. Based on what we know about the evolution of languages, it would take between 500 and 1,000 years for their languages to become distinct.
The team therefore simulated several scenarios including known data points and existing assumptions, such as various population estimates based on the existence or absence of disease. Regardless of the scenario, linguistic diversity peaked between 20,000 and 75,000 languages 1,000 to 3,000 years ago. Then this diversity rapidly diminished. The timing suggests that the intensification of agriculture and the rise of nation-states, such as the Roman and Greek empires, led to a catastrophic loss of languages.
Bowern’s team now hopes to zoom in to understand how linguistic diversity changes over time on a regional scale.
This discovery is likely to inform, but not settle, ongoing debates about the landscape of languages across time. This runs counter to a popular theory that linguistic diversity was at its highest level before the dawn of agriculture, around 12,000 years ago, as well as another theory that links today’s language extinction crisis to the rise of colonialism just 500 years ago.
This opens a new perspective, says Chiara Barbieri, a geneticist studying linguistic diversity at the University of Cagliari in Sardinia, Italy, who finds the idea that so many languages could have been lost over time astounding. There is enormous variation, even among the languages remaining today, in the absence or presence of gendered nouns, articles, clicks to communicate, or tones that convey meaning that non-native speakers cannot even hear. “Have people developed languages with features that we can barely imagine today? she asks herself. “It makes your head spin.”