On 23 March 1839, the Boston Morning Post slipped in 'o.k.' for 'oll korrect', a deliberately botched spelling of 'all correct'. Comic abbreviations were all the rage. Linguist Allen Walker Read tracked down this first known use in the 1960s. A year later, in 1840, the presidential campaign of Martin Van Buren, nicknamed 'Old Kinderhook', made the term popular. Today it's understood almost everywhere on the planet.
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.