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The Handicap Principle: A Missing Piece of Darwin's Puzzle

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Why does the peacock grow that tail? Why does the springbok leap straight up into the air when it sees a predator? Why do people behave heroically? The handicap principle answers these questions, eloquently, simply and with an overwhelming sense of conviction. The peacock is advertising his fitness. He is saying to the female in essence, I am so fit I can carry around this cumbersome adornment and still scratch out a very fine living. The springbok is saying to the predator: don't even think about going after me. I am in such good shape I can waste energy jumping up and down and still have plenty of reserves to outrun you. Save us both the bother and go after someone weaker. (By the way, the springbok jumps straight up instead of sideways because by jumping straight up its performance can be effectively judged by a predator from any direction.) And the man who dives into the swiftly flowing river to save a drowning child is actually advertising his fitness and improving his station in society. He is so fit he can take chances that others dare not. He's the man the women want to mate with.

The Handicap Principle thus is about signals, signals between prey and predator, between one sex and the other, and between the individual and the group. The purpose of these signals is to display in an unequivocal way the fitness of the signaler. Note that such signals have to be "fake proof." They have to be what the authors call "reliable." An animal that can't run fast and has limited resources of energy can't waste them jumping in the air. It needs to get going immediately or to stay hidden if it is to have any chance of survival. A man leads with his chin. That's a signal that he's confident. When men had beards it was a little dangerous to stick your chin out since the other guy might grab your beard and you could be in trouble. People demonstrate wealth by wasting money. This is a "reliable" (if ugly) signal because without an ample supply of money, you can't afford to waste it.

Part of the beauty of this book comes from the personality of the authors, who spent a large part of their lives studying little babbler birds in Israel. I feel I know these little social birds just from the loving descriptions in the text. One can see that even though the Zahavis made their discovery of the handicap principle in 1975 and waited almost two decades before it was generally accepted in the scientific community, they harbor no bitterness, nor is their tone at all gloating. They come across as hard-working field scientists who love their work and nature.

Besides being full of exciting and original ideas, The Handicap Principle is also extremely well written. Each sentence is clear and to the point without the burden of unnecessary jargon or the wordy clumsiness sometimes found in such books. Amotz and Avishag Zahavi took great pride in effectively communicating their ideas to a wide audience. Additionally there are scores of exquisite, loving little black and white drawings by illustrator Amir Balaban of animals, birds, insects and people, etc., illuminating the text.

If you're interested in evolutionary theory, this is a book not to be missed. As Jared Diamond says on the cover, "Read this fine book, and discover what the excitement is all about."

This very readable book covers a wide range of biological behavior, and really demonstrates the reality of the Handicap Principle. Not only am I convinced of its truth, but now understand much more about human behavior than before.

A compelling addition to the literature on natural selection and evolution. The Handicap Principle illustrates with compelling examples the reasons for the evolution of much animal behavior, coloring, and communication. A bit heavy on zoology for non-natural scientists, it however is a must read if you fancy yourself a student of evolution.

This is certainly one of the better books on evolution I have read recently. It is laid out in a remarkably cogent and logical manner, and the writing style is clear, crisp, and interesting. In the first chapter, the authors explain the problem they are trying to explain (why so many animals exhibit certain specific risky behaviours and traits, which at first glance seem counter-intuitive to evolutionary theory), and then present their thesis. Subsequent chapters are devoted to the systematic exploration of their hypothesis, while providing a fair and balanced examination of alternate explanations. Thus the book is a great example of the scientific method being implemented by true scientists, and the authors are to be congratulated for laying their ideas out so clearly and logically.

The risky behaviors and traits in question are those seen in animals like the springbok, the most fit of which literally taunt approaching predators by jumping straight up and down. For many years, this behavior was interpreted as altruistic; the idea being that these springboks were trying to warn the other springboks of the approaching danger.

The Zahavi's present an alternate explanation. They agree that the leaping springboks are definitely trying to send a message to their fellows, but it is not primarily intended to serve as a warning (although it may well serve that secondary purpose to some springboks in the back of the herd who have not yet seen the approaching lion.) The Zahavi's argue that these springboks are trying to show off, to communicate to their peers: "I am so fit, I can waste energy leaping around rather than simply running away. Lady springboks, you should come visit me after the danger has passed; male springboks, do not even think of messing with me." This is no different than the behavior seen in the fastest and most athletic kids playing a game of tag, when one of their slower fellows is "it." Who doesn't have the childhood memory of these kind of kids (usually boys) running around in circles about the hapless "it," dancing about him and taunting him (or her, but usually him), showing off to each other by making increasingly daring passes. Meanwhile, their slower, less fit peers have gotten as far away as possible, for those players know they dare not attempt such "risky" behavior.

Thus, these kinds of activities are all actually designed to increase status with one's peers, and as the Zahavis continue to show, we humans are programmed with the same tendencies as well. Here, I think, it is important to explain that evolutionary theory does not argue that these are consciously decided actions; rather, both we and animals are wired to behave this way, and we do so almost involuntarily. (Thus the handicap principle might explain why an otherwise intelligent person like Bill Clinton literally cannot keep it zipped. He really can't help himself, because among human males there is definitely a pecking order separating those who "score" from those who don't. This does not, of course, excuse the behavior, it simply explains it. But I digress.)

The handicap principle does, in fact, seem to explain a huge number of otherwise mysterious behaviors both in the animal kingdom and in human culture. The giant peacocks tail, or the rich men lighting their cigars with hundred dollar bills. The enormous, unwieldy rack of horns on a male deer's head during mating season, or the young man cruising for chicks in his $60,000 sports car. All designed to show off, to communicate that "I am so strong and successful I can waste resources on extravagances like this."

The Zahavi's even explain heroic, altruistic behavior in this context, and it is difficult to refute. The decision to run into a burning building and rescue someone never seems to be made deliberately - it usually appears to be an impulse - and yet the reward for the person who acts heroically and altruistically (if he survives the action) would, in fact, seem to make it worthwhile in the end. Thus, we may well be wired to impulsively act heroically because there is no doubt that a surviving hero is accorded greatly enhanced status, and the classic archetype of the fawning woman responding to such behaviour with coos of "my hero" shows that we all, deep down, know that such men do, in fact, get laid more often.

The Zahavis give countless examples such as this to explain curious traits and behaviors in the animal kingdom, and for my part, it appears to be an elegant explanation. Now comes the hard part, which the Zahavis acknowledge. The theory must withstand the exquisite scrutiny of scientific study, for it is not like we can interview springboks and ask them why they are leaping and jumping about when a lion approaches. Proving this theory beyond a shadow of a doubt will take time, and we are not yet there. But for the time being, this remains a compelling and viable explanation.

In The Handicap Principle, the Zahavis have created a compelling case for a seemingly paradoxical revelation: Strength may only be demonstrated by showing vulnerability.

The simplest distillation of its central tenets is that interspecies or intraspecies communication must be costly in order to be meaningful. While it would be useful for any animal to be able to view another's cardiovascular health, the body provides few outright signals of its internal function ... or does it? Amazingly, many seemingly useless appendages like peacock's tails do precisely that. If a peacock can grow a perfectly symmetrical, useless tail, chances are it's in good physical health otherwise.

When we pause to try to determine which traits are considered beautiful, the likely candidates are those with no obvious survival value (long lustrous hair, unblemished skin, clear eyes, perfect teeth, symmetry, and artfully placed fat deposits). All of these traits are also the ones most vulnerable to parasites, and the first to fade in the event of poor health or old age. These are the last places an animal will put its nutritional resources if it was worried only about its daily survival. It is their very wastefulness that shows their value. While no one literally wears their hearts on their sleeves, our dermis is a fairly good proxy of our overall health. This is precisely because of its exceptional vulnerability.

Indeed, any time a scientist wants to test material properties, he or she usually has to break the sample that is being tested. It is only by showing vulnerability that true (breaking) strength can be gauged.

Thorstein Veblen's The Theory of the Leisure Class, published in 1899, and Nancy Etcoff's Survival of the Prettiest both form interesting companion pieces to this work. The Zahavis demonstrate that Veblen's concept of conspicuous consumption applies to the animal kingdom as well.

Just like The Origin of Species or The Selfish Gene, the Handicap principle is a theory that has yet to be proven. From a scientific perspective, however, a theory is far more than a guess. Theories can be judged primarily for their explanatory power, and all of these works provide considerable ammunition. While The Handicap Principle is by no means proven, it provides an amazing lens through which to view the world. You'll never look at animals (or yourself) the same way again.

Extrapolating James A Shapiro's concept of "Natural Genetic Engineering", imagine that you are a quantum-consciousness-spirit designing your control cascades ( what's the wave, what's the float ? ).
Genetic Entropy is a problem. Quantum-consciousness only needs an infinitesimal amount of force to tweak things, by analogy to the force required to deflect an asteroid from a collision with earth, if your application of force is COHERENT you don't need a lot of force. So quantum-consciousness can fight Genetic Entropy, but only to a certain degree. What you need, is a MECHANISM to fight Genetic Entropy - how about Sexual Selection ?

Even Dawkins says that Sexual Selection is underrated, I think I saw that in an interview he did with David Attenborough. But what if Sexual Selection were DESIGNED by the peacock-spirit to fight Genetic Entropy, not so that evolution can move forward, that's way too difficult, but merely to avoid backsliding.

I thought that the Zehavis' research and book was outstanding.
I feel this book and their theory is a must for any comprehensive review of the literature on altruism.

One problem with this book is that it refutes other forms of cooperative altruism such as reciprocal altruism instead of combining them with the theory and expanding upon them. The Handicap Principle is one of a few theories on explaining cooperative behavior in different species and the authors here give it a good starting point to their theory. It seems that several theories stemming from evolutionary research need to use the cooperation they often rave about and come together to overcome their flaws.