Charles Darwin ventured that the magnificent trains on male peacocks, which feature ornamental eyespots called ocelli, evolved because of sexual selection. He speculated that there was a single origin, which sexual selection then enhanced. A new genetic study of peacocks and closely related pheasants found that this trait appears in some birds but not others, which suggests that it independently evolved repeatedly.
Article: Keping Sun, Kelly A. Meiklejohn, Brant C. Faircloth, Travis C. Glenn, Edward L. Braun, and Rebecca T. Kimball: The evolution of peafowl and other taxa with ocelli (eyespots): a phylogenomic approach. Proc. R. Soc. B September 7, 2014 281 1790 20140823; doi:10.1098/rspb.2014.0823 1471-2954