TOEFL Speaking Task 3

In biology, organisms often develop traits that seem disadvantageous but actually serve a critical survival function. One such concept is 'costly signaling,' where an animal displays a feature that is energetically expensive or risky to maintain, yet this very cost signals genetic fitness to potential mates or rivals. Because only healthy individuals can afford the high cost, the trait acts as an honest indicator of quality. Predators or competitors may also be deterred by the apparent vigor of the signaler.

Professor: Let me give you a classic example: the peacock's tail. A male peacock grows an enormous, colorful tail that is heavy and makes it harder to fly, and it also attracts predators. That seems terrible, right? But females choose males with the largest, most symmetrical tails. Why? Because if a male can survive despite dragging around such an extravagant tail, it proves he has strong genes, good health, and can evade predators. The tail is a handicap—it costs energy to grow, it slows him down, and it makes him more visible. So when a female sees a magnificent tail, she knows that male must be really fit. In contrast, a sick or weak male couldn't grow such a tail or would be caught quickly. So the tail is an honest signal of quality, not a foolish decoration.