“Prum believes that animals may come to adopt certain aesthetic characteristics not because those traits are adaptive but simply because they are beautiful. This may be because of a sensory bias in the brain—a neurological feature that just prefers shiny things over nonshiny things—or a preference for novelty. But these attributes don’t necessarily signal that there is something better about the peacock with the extravagant tail. The peahen doesn’t like his tail more than others because it suggests he’s a strong and fit potential mate, but just because she likes how it’s shiny, and blue, and large. Prum bases this theory on a lifetime of studying birds like those in the drawers at his lab, many of which have plumage, skeletons, or songs that make it difficult for them to fly or easy to be spotted by predators.”