What Is Zahavi’s Handicap Principle?

Proposed by Israeli biologist Amotz Zahavi in the 1970s, the handicap principle explains how certain costly traits can evolve as honest signals of genetic quality, especially through sexual selection. According to this principle, features like the peacock’s tail are considered “handicaps” because they reduce an animal’s survival chances by making them more visible to predators, requiring more energy to maintain, or hindering movement. Yet, these handicaps persist and even become more elaborate over generations.

How Does the Principle Work?

The core idea is that only the fittest individuals can afford to bear the cost of these extravagant traits. A peacock with a long, heavy tail is advertising to potential mates that he is strong and healthy enough to survive despite this obvious disadvantage. This makes the tail an honest signal—one that cannot be easily faked by weaker males. Females that choose males with the most impressive tails are, in effect, selecting mates with superior genes, thereby increasing the fitness of their offspring.

The Peacock’s Tail as a Classic Example

The peacock’s tail is often cited as the textbook case supporting Zahavi’s handicap principle. The tail’s length, weight, and bright colors do not aid survival; in fact, they make the peacock more vulnerable. However, these very costs are what make the tail a reliable indicator of male quality. Only a truly fit male can thrive while carrying such a handicap, so the trait is maintained in the population through female choice.

Why Not the Other Options?

• Hamilton’s rule deals with kin selection and altruism, not costly signaling.

• The Red Queen hypothesis explains evolutionary arms races, particularly in host-parasite dynamics, not honest sexual signals.

• Haldane’s rule addresses hybrid sterility and inviability in interspecies crosses.

Conclusion

The peacock’s long feather train is a powerful demonstration of Zahavi’s handicap principle. It shows how sexual selection can favor traits that are costly and seemingly disadvantageous, as long as they serve as honest signals of genetic fitness to potential mates.

Correct answer:
(2) Zahavi’s handicap principle