In the early 19th century, Rasmus Rask and then Jacob Grimm (yes, one of the fairy-tale brothers) noticed regular correspondences: where Latin has p, Germanic languages have f. Pater matches 'father', pes matches 'foot', piscis matches 'fish'. Sounds change according to rules, which lets linguists reconstruct lost languages.
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.