A. Zahavi

A. Zahavi emerges as a forceful contrarian in debates over how animal signals evolve. His handicap principle gives an evolutionary explanation for traits that appear to undermine their possessors: an honestly costly display can persuade observers that its bearer is so capable that he can afford the burden. The book subjects this proposal to a demanding test, challenging its logic while stopping short of treating the question as settled. Zahavi’s approach also informs an interpretation of Thomson’s gazelle stotting: conspicuous jumping may be directed chiefly at predators, advertising that the gazelle is a difficult target rather than offering an altruistic warning to its companions.

A Rival Account of Sexual Selection

The discussion of Zahavi begins with a familiar puzzle in sexual selection. The long tails of birds of paradise and peacocks, the large antlers of deer, and other traits that seem to handicap their bearers have often appeared paradoxical: why should a feature that impedes survival become attractive to potential mates? An account of runaway sexual selection explains how female preferences and male traits might reinforce each other over generations. Zahavi offers a competing explanation, one that makes the apparent disadvantage central rather than incidental.

His starting point is that mate choice can be vulnerable to deception. If females select males for strong muscles, a male might evolve an appearance of strength without possessing the underlying ability. A false advertisement would be favored if it were less costly to produce than the quality it imitates. But selection could also favor females able to see through such a display. In Zahavi’s account, males succeed by demonstrating real quality in a way that a pretender cannot cheaply reproduce: the display must be difficult enough to perform that only a genuinely capable male can sustain it.

This principle makes an extravagant trait legible as evidence. A long, cumbersome tail can signal not that its bearer is free of disadvantage, but that he remains viable despite it. The book illustrates the logic with a race: if two runners finish together, while one has carried a sack of coal, observers may infer that the burdened runner is the faster. The display persuades by imposing a cost that turns apparent excess into a claim about capacity.

Testing the Handicap Principle

The author’s response is skeptical, though qualified. He initially sees the theory’s logic leading toward an absurd extreme: if a handicap advertises quality, males with only one leg or one eye might supposedly become attractive. Zahavi answers with a pointed example, noting that some of Israel’s best generals have only one eye. The exchange captures the theory’s provocative appeal, but does not resolve its difficulty.

The more substantial objection concerns inheritance and the cost to offspring. If a handicap is genuinely burdensome, it may penalize the next generation as well as attract mates. For the proposal to work as described, the handicap must not be passed to daughters. The genetic account therefore requires a linked pattern of effects: genes producing the handicap act in sons, while genes producing the preference for that handicap act in daughters. Females favor handicapped males because surviving despite the burden may indicate good qualities in other respects; those other qualities can benefit the offspring and help propagate both the male-trait genes and the preference genes.

In verbal form, this arrangement might be possible, but the book treats verbal plausibility as insufficient. Mathematical geneticists attempting to build a workable model of the handicap principle have not succeeded. That failure could indicate that the principle cannot be made to work, or merely that the attempts have not been clever enough. The author leans toward the former explanation, while acknowledging the uncertainty rather than presenting the model-building problem as a conclusive disproof.

Displays, Rivals, and Mate Choice

Zahavi’s account is set against a less paradoxical way males can demonstrate their superiority: winning contests. Elephant seals acquire and hold harems by defeating males who challenge them, rather than by relying on an aesthetically attractive feature. A harem holder’s repeated success gives females a possible reason to mate with him: his sons may inherit the ability to withstand further challenges. The comparison clarifies the distinction between demonstrating quality through costly appearance and demonstrating it through success against rivals.

The example also limits how freely that choice can be described. A female elephant seal has little option to leave the harem, because its owner may beat her if she tries to stray. The book nevertheless separates that constraint from the broader evolutionary point: females mating with males that win fights may, in some circumstances, benefit their genes. Female preferences for males that hold territories or occupy high status in a dominance hierarchy offer related examples of mating with successful competitors.

These different routes to reproductive success belong to a wider account of conflict between the interests of males and females. Individuals of either sex are treated as tending to maximize their reproductive output over a lifetime, but the difference between the size and number of sperm and eggs can bias males toward promiscuity and less paternal care. Females, in turn, may favor a forceful, competitive male—the book’s he-man strategy—or a domestic-bliss strategy. Ecological circumstances affect which counterstrategy is favored and how males respond; actual breeding systems range across intermediate forms rather than falling neatly into a single type.

From Mating Displays to Gazelle Stotting

The book returns to Zahavi when considering the stotting Thomson’s gazelle, whose conspicuous high jumps have appeared to be an instance of self-endangering altruism. Their display differs from bird alarm calls, which are described as discreet: the gazelles jump ostentatiously, seemingly drawing attention to themselves. This contrast makes the behavior a sharper challenge for an explanation based on benefit to the group.

Zahavi’s interpretation reverses the apparent audience. The jumping may affect the behavior of other gazelles, but that effect could be incidental; the primary signal, he proposes, is aimed at the predator. A gazelle that jumps high advertises its condition and capacity to escape, encouraging the predator to pursue a neighbor that seems easier to catch. Because many mammalian predators tend to select old or unhealthy prey, the display could communicate that its performer is neither. On this reading, stotting is not an altruistic sacrifice for the herd but a self-interested attempt to redirect danger.

The author presents this as a daring explanation, not a demonstrated fact. Its force lies in making a supposedly suicidal display intelligible as an advertisement with a different recipient and payoff. Across both mating displays and stotting, Zahavi’s recurring challenge is to ask whether an apparent signal of generosity or disadvantage can instead reveal the interests of the individual producing it—and whether the cost itself is what makes the signal credible.