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.

• Prum describes a study that is showing how statistically unlikely it is that the bird is able to predict any adaptation features from saturation of the feathers, the ability to collect only blue objects, or weather in one moment of a specific dance a bird had a tail up or down.
• Some of the genetic features that the birds are selecting are bringing whole species towards extinction (one type of bird is making sound by oscillating its wings. In order to be able to do that they have filled bones (all other birds have hollow bones). This, in turn, make them heavier and renders their bodies more difficult to fly.)
• Why evolution process would be so inefficient? Features like intricate feather decorations of Great Argus (see photo below) takes thousands of generations to develop and has no proved utility. (watch Argus display on YouTube)
• Some of the traits are purely random. Prum describes a species of a bird from Papua New Guinea. There could be two groups that are as close as 20 km apart, that has different aesthetic preferences – birds selecting for blue and yellow displays. He describes how this mechanism might have happened. There is one group of birds and that don’t have a strong color preference, but there are is a bird slightly preferring blue over the yellow. This bird will choose mates that use a slightly bluer display. If two birds that prefer blue mate their offspring will be selecting for blue even stronger. This is a purely random aesthetic preference that is like a self-reinforcing feedback loop that will be strengthened in the following generations.

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

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Great Argus Feathers