Is the peacock merely beautiful or also honest?

摘要

Darwin proposed the theory of sexual selection to account for the evolution of extravagant secondary sexual characters often seen in males because he argued that utilitarian natural selection cannot permit their evolution. Although the idea of sexual selection was, disbelieved or neglected for a long time, today it constitutes an active area of research. Starting with Darwin, the enormous, cumbersome train of the peacock has been the prime example of sexually selected traits. And yet, almost nothing relevant to sexual selection was known about the peacock until very recently. In the last ten years or so, observations and experiments on a free-ranging, feral population of the Indian peacock in the Whipsnade Park in Bedfordshire in the UK and some experiments in a commercial peacock farm that breeds birds for food and as show birds, by Marion Petrie and her colleagues have finally justified the peacock as an icon of sexual selection by female choice. The peacock appears to fulfil nearly every expectation of the theory of sexual selection: peahens prefer peacocks with elaborate trains probably recognizing them by the symmetry of their trains and benefit from doing so because of improved survival of their chicks. Peacocks with elaborate trains themselves appear to be better survivors with larger fat reserves and higher levels of immunocompetence. These findings support theories which suggest that peacocks with elaborate trains are selected because of the handicap they carry rather than in spite of it. Thus the peacock's train is not merely beautiful but is also an honest indicator of male quality. Although the peacock is deeply entrenched in Indian mythology, culture and folklore and it is widely distributed in the country, research from India has regrettably made no significant contribution to recent research justifying the peacock as a prime example of sexual selection and making it a frontrunner in modern studies of sexual selection.