Seminar Two
Evolution of sexuality
Female choice in sexual selection

Let's imagine a scenario in which sexual selection occurs. If a mutation in a gene predisposes a female to choose a more colorful male over a less colorful one, the choice will often be to her reproductive advantage, because males with brighter colors tend to have fewer parasites (avian parasites are plentiful, with nearly a dozen kinds of feather mites alone). Her daughters will inherit her preference for colorful males. This kind of sexual selection is called intersexual selection (meaning between-sex selection), and in this case, it involves female choice. What does the dramatic rump feather display of the peacock tell us?

In spite of a 2008 study by Mariko Takahashi, which failed to find evidence of female choice in pea hens, the hypothesis of female choice still appears to be the most likely explanation for this cumbersome structure in peacocks. (This is the way science proceeds, with anticipation of challenges to even long-held beliefs.) The peacock carries a big handicap to his survival: his long feather train makes it harder to hide or escape from a predator. In this sense, natural selection opposes sexual selection.

Tests of the female choice hypothesis have been overwhelmingly supportive in most birds and in many other vertebrates as well. For most animal species studied, males compete more for females than vice-versa. In about one percent of birds the roles are reversed—females are larger and may be more colorful, and males care for the eggs (examples: phalaropes and jacanas).