There are few things as familiar to us as the experience of laughing and crying. Studying the two emotional expressions side to side is a way to see our species anew. A way of linking what we share with other mammals to that which sets us apart from all other species. Pulling laughing and crying onto center stage in all their theatrical glory creates a scene of which philosophers and anthropologists have long dreamt: a vision that is uniquely human. Laughing and crying are in many ways physiological and psychological opposites, but these complex behaviors are not exact reversals of the same bodily processes. Nor have researchers told me that they are connected in any biologically relevant way. But zooming out of narrow scientific definitions, digging into our evolutionary history, focusing on the disorders of laughing and crying, looking to the stage where actors and actresses come alive through their tears, there emerges a puzzle of psychology, neuroscience, evolutionary theory, and neurology slowly snapping together.