Ubykh, a language of the Caucasus, had around 80 consonants but only two or three vowels, one of the richest consonant inventories ever described. Its speakers, exiled to Turkey in the 19th century, gradually switched to Turkish. Its last fluent speaker, Tevfik Esenç, died in 1992, after helping linguists record it.
In Kuşköy, a mountain village in northern Turkey, people talk across valleys by whistling Turkish. A 2015 study showed that whistled Turkish draws on both hemispheres fairly evenly, whereas spoken Turkish relies mostly on the left. The physical form of the signal, it turns out, matters to the brain.
Speech has no gaps between words. In 1996, researchers played 8-month-old babies a continuous stream of made-up syllables for just two minutes. The infants picked out the 'words' by tracking which syllables tend to follow one another. That's probability calculation, done without a calculator or any visible effort.