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That is, genes for long tails and for preferring long tails become linked.
The taste for long tails and tail length itself may therefore become correlated, tending to increase together.
—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.
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.
For instance in the breeding season sexual selection in frogs occurs with the males first gathering at the water's edge and making their mating calls: croaking.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.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.In most existing species the runaway process must have been already checked, and we should expect that the more extraordinary developments of sexual plumage are not due like most characters to a long and even course of evolutionary progress, but to sudden spurts of change.