For Charles Darwin, the problem of the peacock's tail, in light of his theory of natural selection, was vexing in the extreme.
Indeed, in 1860, writing to Asa Gray, his most ardent American champion, Darwin confessed: "The sight of a feather in a peacock's tail, whenever I gaze at it, makes me sick!"
In his struggle to explain why such extravagant and seemingly burdensome features existed, the great English naturalist struck upon the idea of sexual selection -- that showy traits such as the Peacock's ornamentation were an advantage in the mating game that outweighed other disadvantages.