The human voice is capable of forming a plethora of incredibly different sounds. So many, in fact, that each individual language (contains) only a subset of potential sound units, or phonemes. What factors determine whether a phoneme enters common use, or is relegated to silence? It turns out, (geography) may play a role.

One phoneme that occurs in only about 20 percent of the world's languages is the ejective consonant, such as p' or k'. Caleb Everett, an anthropologist at the University of Miami, decided to map where this sound occurs. He took a (sample) of 567 languages spoken around the world, and compared the locations and altitudes of those that either contained or ignored ejective consonants.

Everett discovered that languages that included (ejective) consonants were generally spoken at a higher elevation than those that did not. His research is in the journal PLOS ONE. [Caleb Everett,Evidence for Direct Geographic Influences on Linguistic Sounds: The Case of Ejectives]

Everett suggests that the (sounds) are more popular at altitude because lower air pressure may make it easier to produce the burst of air that is a key characteristic of ejective consonants. Which is P-retty C-ool.