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This causes the peacocks with fewer eyes to die out and those with more to become more common.Sexual selection is a mode of natural selection where members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (intrasexual selection).Fisher understood that female preference for long tails may be passed on genetically, in conjunction with genes for the long tail itself.Long-tailed widowbird offspring of both sexes inherit both sets of genes, with females expressing their genetic preference for long tails, and males showing off the coveted long tail itself.—Ronald Fisher, 1930 This causes a dramatic increase in both the male's conspicuous feature and in female preference for it, resulting in marked sexual dimorphism, until practical physical constraints halt further exaggeration.A positive feedback loop is created, producing extravagant physical structures in the non-limiting sex.The females then arrive and choose the males with the deepest croaks and best territories.Generalizing, males benefit from frequent mating and monopolizing access to a group of fertile females.
The taste for long tails and tail length itself may therefore become correlated, tending to increase together.Sexual selection can lead typically males to extreme efforts to demonstrate their fitness to be chosen by females, producing sexual dimorphism in secondary sexual characteristics, such as the ornate plumage of birds such as birds of paradise and peafowl, or the antlers of deer, or the manes of lions, caused by a positive feedback mechanism known as a Fisherian runaway, where the passing-on of the desire for a trait in one sex is as important as having the trait in the other sex in producing the runaway effect.Although the sexy son hypothesis indicates that females would prefer male offspring, Fisher's principle explains why the sex ratio is 1:1 almost without exception." His work divided sexual selection into male-male competition and female choice.These views were to some extent opposed by Alfred Russel Wallace, mostly after Darwin's death.
It is important to notice that the conditions of relative stability brought about by these or other means, will be far longer duration than the process in which the ornaments are evolved.