The peacock’s plumage seems not only pointless, it’s also an impediment. Then, how did it evolve?
Peacock’s plumage: Asset or liability?
There are few animals in nature more resplendent than a male peacock in full display, with his iridescent blue-green tail, studded with eyespots, fanned out in full glory behind a shiny blue body. But the bird seems to violate every aspect of Darwinism, for the traits that make him beautiful are at the same time maladaptive for survival, writes Jerry Coyne in why Evolution is ture
The long tail
makes it hard for the birds to escape predators, especially during the monsoons when a wet tail is literally
a drag. The sparkling colours attract predators. And a lot of metabolic energy is diverted to the striking tail, which must be completely regrown each year
The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick! … It cannot be supposed,
for instance, that peacocks should take such pains in erecting, spreading, and vibrating their beautiful
plumes before the females for no purpose
Charles Darwin
Sexual Selection
Darwin then developed the idea of sexual selection, that females chose males with the best ornaments, and hence elegant peacocks have the most offspring. A group in England found a strong correlation between the number of eyespots in a male’s tail feathers and the number of matings he achieved
But is it possible that the females choose another aspect of the males, and this just happens to be correlated with plumage? To rule this out, the group cut 20 eyespots from every male in a group of peacocks, and found deornamented males each averaged 2.5 fewer matings than the control group