Differences of Human Languages Driven by Climate and Environment

Climate of Human Habitats May Have Driven Differences in Human Language
Factors like tree cover, temperature and the rugged terrain shaped how different our languages sound, according to new research. Navesh Chitrakar/Reuters

What does it take to communicate? If you're on a crowded train platform, shouting to your friend 20 yards away, it might take simplification. Imagine trying to say "unequivocally." It probably wouldn't work out. Any words with lots of consonants and complicated syllables would likely get garbled, swallowed up by the noise around you, blocked by the throng of bodies and kiosks and other objects in your way. So you keep it simple. A plain, old "yeah" is probably going to reach her ears better.

Now imagine extrapolating these constraints of acoustics to the whole human population, roaming the entire earth. Picture societies developing in myriad ecological habitats. At the same time, they're evolving their own distinct languages. As it turns out, the characteristics of languages have a lot to do with the environment—specifically the climate and topography—they emerged in, according to new research that will be presented Wednesday at the 170th Meeting of the Acoustical Society of America (ASA) in Jacksonville, Florida.

People from cultures that originated in hot, tree-covered regions now tend to speak languages with fewer consonants and simpler syllables in part because, according to the researchers, both hot air and vegetation make transmission of higher frequency sounds (like those made with consonants) less reliable. According to Ian Maddieson, a linguist at the University of New Mexico and the study's primary researcher, this is a major reason that languages spoken by people in tropical areas use many more vowels and simpler syllable structures than their counterparts in more open, colder places. Vowels transmit at lower frequencies, and simpler syllable structures are less likely to be garbled by having trees in their way.

Rough terrain, like mountains and cliffs, have a similar effect on language as vegetation. People in these regions also speak with simpler syllables and more vowels. Wind and rain appear to play roles in shaping human languages in different areas as well, Maddieson says. All these ecological factors account for about a quarter of the variation in how consonant-dominant a language turns out to be.

The research team looked at a database of 700 written languages from across the globe. They excluded languages spoken by more than 5 million people, like English and Mandarin Chinese, because the speakers of major languages are too spread out to pin down specifics about their ecological habitats. In the end, they analyzed 633 languages for syllable structure, vowel prevalence and use of consonants. They overlaid this linguistic data on maps showing where each language was spoken and then compared that to maps of climate conditions. They found that the average annual precipitation, average annual temperature, vegetation density and "rugosity" (or mountainousness) of a region, as well as its elevation, all correlated to characteristics of that region's language. The particular acoustics of environments, they concluded, account for a lot of how differences in human languages developed.

Maddieson says these findings suggest that the acoustic adaptation hypothesis, which has mostly been applied to describe birds, can be applied to humans too. Since the 1970s, researchers have observed that birdsong appears to depend heavily on the ecological habitat each particular species calls home. "The highest notes and the range of notes are lower in forested kinds of environments compared to open environments in birdsong," Maddieson says. Birds evolved their communication, then, according to acoustic factors similar to the ones Maddieson's team studied in relation to humans. But unlike birds, humans are one species, which Maddieson says makes this use of the hypothesis particularly compelling.

"Now, within a single species of bird, they're finding that the birds that live in cities with a background noise of cars, etcetera, are singing in higher pitch notes than birds that live in rural areas," he says. "The birds are adapting to the traffic noise. This is really more what we're talking about with humans. The same species adapting to their environment."

Could humans who live in urban areas, then, be currently morphing their rural-born language to better suit those conditions?

"Over time, I would expect that to evolve. But we haven't been living probably long enough yet in noisy urban environments yet," Maddieson says. "But come back in a few more years, and you might see that, yes."