On 14 February 842, in Strasbourg, two of Charlemagne's grandsons, Louis the German and Charles the Bald, allied against their brother Lothair. To be understood by the other's troops, each swore in the other side's language: Louis in Romance, Charles in Germanic. Recorded by the chronicler Nithard, these Oaths of Strasbourg are the oldest known text in the ancestor of French.
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.