The Handicap Principle

A Missing Piece of Darwin's Puzzle

by Amotz and Avishag Zahavi

English translation: Melvin Patrick Ely and Naama Zahavi-Ely

Ever since Darwin, the extravagance in animal displays--elaborate mating rituals, lavish decorative displays, complex songs, calls, and dances--has fascinated and perplexed human observers. The Handicap Principle offers a unifying theory that brilliantly explains many previously baffling aspects of animal signaling and endows human behaviors with surprising new significance.

The Handicap Principle illuminates an astonishing variety of behaviors in animals ranging from amebas and ants to peacocks, gazelles, and humans. Essentially, the Zahavis assert that for animal signals to be effective, they must be reliable, and to be reliable they must impose a cost, or handicap, on the signaler. When a gazelle sights a wolf, for example, it jumps high into the air several times before it flees; the gazelle is signaling, in a reliable way, that it has seen the wolf and is in good enough physical condition to escape the predator. A human parallel occurs in children's games of tag, in which faster players will often taunt their pursuer before running away. By momentarily handicapping itself--expending precious time and energy in a display of prowess--the animal (or human) underscores the truthfulness of its signal and spares both prey and predator the exhaustion of a pointless chase. In a similar way, the enormous cost a peacock incurs by carrying elaborate and heavy tail feathers, which interfere with movement and flight, reliably communicates its quality and thus its desirability as a mate.

One of the book's most important applications of the Handicap Principle is to the evolutionary enigma of animal altruism. The authors show that, when one animal helps another, it handicaps itself--takes a risk or endures a sacrifice--not mainly to benefit its kin or social group, but rather to increase its own prestige within the group and thus signal its desirability as a partner or its power as a rival.

The Zahavis discuss the ways the Handicap Principle works in human social life, touching on subjects as diverse as body features, the evolution of art, verbal language versus nonverbal communication, and the role of sex in testing the social bond. Homosexuality, human altruistic drives, and suicidal behavior are all explained within the framework of evolution.

Elegantly and accessibly translated and enlivened with vivid examples and captivating illustrations, The Handicap Principle conveys to the nonspecialist reader perhaps the most important advance in the study of animal behavior to appear in the last several decades. The book allows us not only to hear what animals are saying to each other--and to understand why they are saying it--but also to gain a richer understanding of the forces guiding human behavior.

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