The thatched roof held back the sun’s rays, but it could not keep the tropical heat at bay. As everyone at the research workshop headed outside for a break, small groups splintered off to gather in the shade of coconut trees and enjoy a breeze. I wandered from group to group, joining in the discussions. Each time, I noticed that the language of the conversation would change from an indigenous language to something they knew I could understand, Bislama or English. I was amazed by the ease with which the meeting’s participants switched between languages, but I was even more astonished by the number of different indigenous languages.
Thirty people had gathered for the workshop on this island in the South Pacific, and all except for me came from the island, called Makelua, in the nation of Vanuatu. They lived in 16 different communities and spoke 16 distinct languages.
In many cases, you could stand at the edge of one village and see the outskirts of the next community. Yet the residents of each village spoke completely different languages. According to recent work by my colleagues at the Max Planck Institute for the Science of Human History, this island, just 100 km long and 20 km wide, is home to speakers of perhaps 40 different indigenous languages. Why so many?
We could ask this same question of the entire globe. People don’t speak one universal language, or even a handful. Instead, today our species collectively speaks over 7,000 distinct languages.
And these languages are not spread randomly across the planet. For example, far more languages are found in tropical regions than in the temperate zones. The tropical island of New Guinea is home to over 900 languages. Russia, 20 times larger, has 105 indigenous languages. Even within the tropics, language diversity varies widely. For example, the 250,000 people who live on Vanuatu’s 80 islands speak 110 different languages, but in Bangladesh, a population 600 times greater speaks only 41 languages.
Why is it that humans speak so many languages? And why are they so unevenly spread across the planet? As it turns out, we have few clear answers to these fundamental questions about how humanity communicates.
Some ideas, but little evidence
Most people can easily brainstorm possible answers to these intriguing questions. They hypothesize that language diversity must be about history, cultural differences, mountains, or oceans dividing populations, or old squabbles writ large—“we hated them, so we don’t talk to them.”
The questions also seem like they should be fundamental to many academic disciplines—linguistics, anthropology, human geography. But, starting in 2010, when our diverse team of researchers from six different disciplines and eight different countries began to review what was known, we were shocked that only a dozen previous studies had been done, including one we ourselves completed on language diversity in the Pacific.
These prior efforts all examined the degree to which different environmental, social, and geographic variables correlated with the number of languages found in a given location. The results varied a lot from one study to another, and no clear patterns emerged. The studies also ran up against many methodological challenges, the biggest of which centered on the old statistical adage–correlation does not equal causation.
We wanted to know the exact steps that led to so many languages forming in certain places and so few in others. But previous work provided few robust theories on the specific processes involved, and the methods used did not get us any closer to understanding the causes of language diversity patterns.
For example, previous studies pointed out that at lower latitudes languages are often spoken across smaller areas than at higher latitudes. You can fit more languages into a given area the closer you get to the equator. But this result does not tell us much about the processes that create language diversity. Just because a group of people crosses an imaginary latitudinal line on the map doesn’t mean they’ll automatically divide into two different populations speaking two different languages. Latitude might be correlated with language diversity, but it certainly did not create it.
Read more: Quartz