As people are getting healthier, richer, safer, and freer, they are also becoming more literate, knowledgeable, and smarter. Early in the 19th century, 12 percent of the world could read and write; today 83 percent can. Literacy and the education it enables will soon be universal, for girls as well as boys. The schooling, together with health and wealth, are literally making us smarter—by thirty IQ points, or two standard deviations above our ancestors.
