Of Partners and Peacocks

IN THE FIELD OF EVOLUTIONARY biology, a phenomenon known as Fisher’s runaway provides an interesting nuance to the theory of natural selection. Under natural selection, females of a species are typically drawn to males who offer their offspring the best chance of survival. Yet, in cases of a Fisher’s runaway (also known as runaway selection), the attributes that make the male more attractive for mating can, over time, reduce the survival prospects for the species as a whole.

The classic example of a Fisher’s runaway is the peacock. Although the female peahen is attracted to the peacock’s large, colorful tail, the tail itself offers no advantage for survival. In fact, the opposite is true: The bright colors attract the attention of predators, and the cumbersome size reduces the potential for a successful escape. Thus, to mate on the basis of large, colorful tails is to bring potential ruination to the entire species.

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