What makes us human? Various authors have dished out various reasons in recently published books. From culture to cooking to creativity (see Fuentes’s The Creative Spark I reviewed previously). Caleb Everett, a professor of linguistic anthropology, here makes the point that the invention of numbers, which could be considered another instance of human creativity at work, has been an instrumental tool in allowing humans to transform the world. Without them, quantities exist, but we have only a vague awareness of them.