An essential feature of any society is the capacity of its members to distinguish one another from outsiders and to reject outsiders on that basis. My project pursues a remarkable fact: Among animals, only certain social insects and humans can form huge societies, which is because their membership is anonymous—members do not need to distinguish each other as individuals for a group to remain unified. Rather, their societies are instead bonded by shared identity labels, such language and rituals in humans. (Contrast this with societies of all nonhuman vertebrates, which I have shown in a recent scientific publication are limited at most 200 members by the necessity that each animal recognizes every other member individually.) The ability to form anonymous societies is a complex trait that must have arisen in humans well before agriculture, but has made expansive nations possible today. At NESCent, I will explore the ramifications of this fact by preparing a book for a lay audience aimed at bridging several disciplines in my examination of the evolution of human societies.