A large majority of evolutionary biologists are explaining every process in evolution trough a mechanism of natural selection. They claim that all animals are selecting their mates solely based on adaptation skills. This process, often called, survival of the fittest explains mate selection as the process of decoding whether their potential offspring will be genetically fit and could survive and thrive in their environment. If a bird is yellow, it must be that way for a reason (it might help escape predators, help catch pray or save energy). Peacock tail is explained in terms of the theory of honest signaling. The larger and heavier the tail is the fitter potential mate has to be to survive.
Richard Prum is challenging this view and thinks that there is a purely aesthetic mechanism in play. Many animals, he believes, have aesthetic sense and some are largely selecting mates based on beauty. Prum is studying Manakin birds. Manakins is a group of about 50 species of birds that use elaborate displays to attract mates (think Peacock). They use intricate art like installations, complex dances, or have rich feather ornaments to impress their mates.
Many of evolutionary biologist are discounting Prum's theories as non-darwinian. But in fact Darwin himself said that whenever he saw a peacock tail it made his head spin. Peacock represented a hole in his theory of natural selection. It is a little known fact, but Darwin was exploring the same ideas at the end of his career. Eventually he regarded the sexual (or esthetic) selection as a parallel force to the natural selection.
I made this summary from Richard Prum on Rob Reid Show #33 podcast
Great Argus Feathers