In the late 1970s, Nicaragua opened schools for deaf children who had until then lived isolated, with only simple home gestures. Brought together, they spontaneously created a sign language. Each new cohort of pupils made it more systematic and grammatical. Linguists got to watch the birth of a language almost in real time.
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.