In warm, moist climates, human languages developed with more complex linguistic tones than did those in colder, drier regions.
It is thought that language is not influenced by ecological factors. However, Caleb Everett at the University of Miami in Coral Gables, Florida, and his colleagues concluded the opposite after looking at studies of vocal-cord biology and comparing the geographic origins of more than 3,700 languages with the humidity and annual average temperatures of those regions. The vocal-cord data showed that cords produce sounds of varying pitch more accurately in moist air than in dry air. Languages with complex tone, such as Mandarin Chinese, originated mainly in warm, moist climates, whereas languages such as English, which have little or no tone, came from arid or cold regions.