There are about 7,000 languages in the world, and they are constantly evolving and changing. But it's a bit of a mystery why languages change the way they do. Anthropologist Caleb Everett of the University of Miami believes he may have found some of the first evidence that environment can influence the way people speak.

"I do remember standing up from my desk and saying, 'Wow, this is really striking,'" said Everett.

He knew that a small proportion of the world's languages use a sound called an "ejective consonant" - a sound made by pressurizing air in the back of the throat.

To hear what one sounds like, say "kah" - but don't breathe out on the "k" sound. The air you need to make the sound comes from pressure in your throat alone. What you just said - "k'ah" - is the word for "bitter" in the Kekchi Maya language of Guatemala and Belize.

You can turn nearly any consonant into an ejective: "t'ah," or "p'ah," or "s'ah." Plenty of languages use these sounds, including six you can hear on VOA - Ethiopian Oromo and Amharic, Nigerian Hausa, Georgian, Armenian, and Korean.

Everett wondered if languages with ejectives might have something else in common. Because ejective consonants involve compressing air in the back of the throat, he thought that making the sounds at higher elevation - where there is less air pressure - might be easier. He took information on about 600 languages - 92 of which use ejective consonants - and started comparing the altitudes at which they are spoken.
He quickly found that 87 percent of languages with ejectives are spoken in and around areas of high elevation, at least 1,500 meters above sea level.

"I was sitting here at my desk," said Everett, "and I looked at the data, and I thought, 'Okay, it sort of works for North America, it works for South America - wow, it really works in Africa, and it works in Eurasia ... There's really nowhere that it doesn't work!'"

So far, Everett said, this is just an intriguing observation; he has no idea whether high elevation causes these sounds to develop, or if his findings are just an interesting coincidence.

If altitude is leading languages to develop more ejectives - perhaps because making these sounds is easier at lower air pressure - then this is some of the first evidence that environment can affect language development.

Everett also wondered if the physical process of making these unique sounds helps speakers retain moisture when they talk, lessening the risk of dehydration, which contributes to altitude sickness.  

"That would be a pretty big implication for the evolution of language," he said, "because it would suggest that languages have evolved in certain areas with a very slight health benefit of some kind."

The anthropologist said future experiments are necessary to investigate these questions, and to reveal how - or whether - the environment affects the way we speak.