Sir Ronald Fisher had suggested then that females need no better reason for preferring long tails than that other females also prefer long tails. At first such logic sounds suspiciously circular, but that is its beauty. Once most females are choosing to mate with some males rather than others and are using tail length as the criterion—a big once, granted, but we’ll return to that—then any female who bucks the trend and chooses a short-tailed male will have short-tailed sons. (This presumes that the sons inherit their father’s short tail.) All the other females are looking for long-tailed
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