Until now, linguists believed language was only affected by environment in terms of vocabulary. But the new study reveals a strong correlation between high-altitude environments and consonant sounds produced with an intense burst of air, called ejective consonants.
Caleb Everett from the University of Miami compared the sounds used in 600 languages, 92 of which contained ejectives, with the regions they are commonly spoken. Everett input the coordinates of languages into Google Earth to create a linguistic map.
"I was really surprised when I looked at the data and saw that it correlated so well," Everett said. "It really does not rely very much on my interpretation."
The findings, published in the journal PLOS ONE, show that 87 percent of the languages with ejectives included in the study are located within 500 kilometers of a high-altitude region. The findings also indicate that as elevation increases, so does the likelihood of languages with ejectives.
"This is evidence that geography does influence phonology -- the sound system of languages," explained Everett.
Ejectives -- absent in the English language -- were found in languages spoken on, or near, five out of six major high altitude regions where people live.
"Ejectives are produced by creating a pocket of air in the pharynx then compressing it. Since air pressure decreases with altitude and it takes less effort to compress less dense air, I speculate that it's easier to produce these sounds at high altitude," Everett said.
Making ejective sounds may reduce the amount of air exhaled from the lungs, and decrease dehydration in high altitudes.
According to the results, the only high elevation region where ejectives are absent is the Tibetan plateau. People there have a unique adaptation to high altitude that may account for this fact.
Previous studies have shown that Tibetan people breathe at a faster rate than other high altitude populations. This is believed to be an adaptation to the climate and results in a reduction of the effects of hypoxia in high altitude.
"The results of the study suggest that ecological factors may shape the structure of language in ways that have gone unrecognized," Everett said.