"[R]ecently, Caleb Everett, a linguist at the University of Miami, made a surprising discovery that suggests the assortment of sounds in human languages is not so random after all. When Everett analyzed hundreds of different languages from around the world, as part of a study published today in PLOS ONE, he found that those that originally developed at higher elevations are significantly more likely to include ejective consonants. Moreover, he suggests an explanation that, at least intuitively, makes a lot of sense: The lower air pressure present at higher elevations enables speakers to make these ejective sounds with much less effort. (...)" - Amira

"[H]e found that 87 percent of the languages with ejectives were located in or near high altitude regions (defined as places with elevations 1500 meters or greater), compared to just 43 precent of the languages without the sound. Of all languages located far from regions with high elevation, just 4 percent contained ejectives. And when he sliced the elevation criteria more finely—rather than just high altitude versus. low altitude—he found that the odds of a given language containing ejectives kept increasing as the elevation of its origin point also increased. (...) As a result, over the thousands of years and countless random events that shape the evolution of a language, those that developed at high altitudes became gradually more and more likely to incorporate and retain ejectives. Noticeably absent, however, are ejectives in languages that originate close to the Tibetean and Iranian plateaus, a region known colloquially as the roof of the world." - Amira