Bright colors, long tails, and dances of seduction: they may hurt a bird's chances of survival in the wild, but they seem to increase the chances of reproduction. Is this all part of natural selection or is sexual selection its own force in the bird world? Is there such a thing as beauty for beauty's sake? What can we learn from birds about the human experience of beauty? Listen as author and naturalist Matt Ridley speaks with EconTalk's Russ Roberts about a puzzle that kept Darwin up at night and that still troubles modern evolutionary biologists.