There are a little over 7,000 living languages in the world. Yet according to Ethnologue, more than half of the global population speaks one of just 23 of them. At the other end, thousands of languages have only a few thousand speakers or fewer. Around 40% are now endangered, often because they're no longer passed on to children.
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.