It has been said that supreme enlightenment is reflected in the holy smile of the Buddha. Yet, the Victorians thought of open-mouthed smiling as obscene, and nineteenth-century English and American slang equated "smiling" with drinking whisky. Every smile is the product of physical processes common to all humans. But since the dawn of civilization, the upward movement of the muscles of the face has carried a bewildering range of meanings. In A Brief...