Physical attraction is usually one of the first traits that draws couples together. And it’s no different in the animal kingdom. Yale ornithologist Richard Prum joins us to talk about how various creatures have changed their physical appearances in order to attract a mate – and about what animal courtship has taught us about human sexuality. His new book is called “The Evolution of Beauty: How Darwin’s Forgotten Theory of Mate Choice Shapes the Animal World – and Us” (Doubleday).