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.