What Is Sexual Selection?

Sexual selection is a form of natural selection that arises from differences in mating success among individuals. While natural selection favors traits that enhance survival, sexual selection favors traits that increase an individual’s chances of attracting mates and reproducing. In many species, this leads to the evolution of elaborate ornaments, displays, or behaviors—often seen in males—that are used to impress potential mates.

The Peacock’s Tail and Darwin’s Dilemma

Charles Darwin himself was puzzled by the peacock’s tail. He noted that such a large, colorful, and cumbersome feature would likely hinder survival by making the bird more visible to predators and less agile in flight. Yet, the tail persisted and even became more extravagant over generations.

Darwin resolved this puzzle with his theory of sexual selection. He proposed that peahens (female peafowl) prefer to mate with males that have the most impressive tails. As a result, males with larger, more colorful tails have greater reproductive success, passing these traits on to their offspring.

How Sexual Selection Works in Peafowl

Research has shown that peahens consistently choose males with longer trains and more eyespots. These features act as honest signals of health and genetic quality—only the fittest males can afford the energetic costs and increased predation risks associated with such extravagant tails. This is known as the “handicap principle,” where the tail’s costliness ensures its reliability as a signal of male fitness.

Over time, this preference drives the evolution of even more elaborate tails, as each generation of females selects for the most impressive displays. This process is a classic example of intersexual selection, where female choice leads to the amplification of male ornaments.

Why Not Natural, Diversifying, or Group Selection?

• Natural selection alone cannot explain the peacock’s tail, as its extravagance can reduce survival chances. It is the reproductive advantage, not survival, that maintains the trait.

• Diversifying selection favors extreme traits at both ends of a spectrum, but the peacock’s tail is specifically driven by mate choice, not by adaptation to different environments.

• Group selection involves traits that benefit the group rather than the individual, but the peacock’s tail benefits individual males in the mating game.

Scientific Evidence

Classic studies have demonstrated that males with more elaborate tails mate more frequently and sire more offspring. Offspring of these males also tend to be healthier and more viable, supporting the idea that the tail signals genetic quality.

Conclusion

The peacock’s tail is a quintessential example of sexual selection in action. Its evolution is driven by female preference for elaborate male ornaments, resulting in a spectacular display that balances the costs of survival with the rewards of reproductive success. This phenomenon highlights the intricate dynamics of evolution and the power of mate choice in shaping the diversity of life.

Correct answer:
(3) sexual selection