As Steven Pinker has observed, “No mute tribe has ever been discovered, and there is no record that a region has served as a ‘cradle’ of language from which it spread to previously languageless groups.” Speech came naturally—it did not have to be invented. But writing did… Though linguists have documented more than three thousand languages currently being spoken throughout the world, only about a hundred of those languages have been written down. What’s more, over all of human history, writing was independently invented only a few times, and it made its way around the world mainly through cultural diffusion, being borrowed or adapted from existing systems rather than being repeatedly reinvented.

— From Leonard Mlodinow’s The Upright Thinkers. The Steven Pinker quote is from his book, The Language Instinct (1994).