Holt: V. S. Ramachandran, the brain researcher, has a theory about the origin of laughter — that when you're in the jungle and there's an apparent threat, the first member of the kinship group to notice that it's not a real threat emits this stereotyped vocalization. And it's contagious, so everyone starts laughing. That's also the basis of the relief theory of humor, that there's a release of the energy you had summoned up to solve some puzzle. Kant said that the essence of humor is a strained expectation dissolving into nothing.