The Rise and Fall of the Third Chimpanzee

by Jared Diamond

  Zahavi’s theory as he proposed it concerned the broad problem of animal communication. All animals need to devise quick, easily understood signals for conveying messages to their mates, potential mates, offspring, parents, rivals, and would-be predators. For example, consider a gazelle that notices a lion stalking it. It would be in the gazelle’s interests to give a signal that the lion would interpret to mean, ‘I am a superior, fast gazelle! You’ll never succeed in catching me, so don’t waste your time and energy on trying.’ Even if that gazelle really is able to outrun a lion, giving a signal that dissuades the lion from trying would save time and energy for the gazelle too.

  But what signal will unequivocally tell the lion that it is hopeless? The gazelle cannot take the time to run a demonstration 100-yard dash in front of every lion that shows up. Perhaps gazelles could agree on some quick arbitrary signal that lions learn to understand, such as that pawing the ground with the left hind foot means ‘I claim that I’m fast!’ However, such a purely arbitrary signal opens the door to cheating; any gazelle can easily give the signal regardless of its speed. Lions will then catch on that many slow gazelles giving the signal are lying, and lions will learn to ignore the signal. It is in the interests both of lions and of fast gazelles that the signal be believable. What type of signal could convince a lion of the gazelle’s honesty?

  The same dilemma arises in the problem of sexual selection and mate choice that I discussed in Chapters Five, Six, and Nine. This is especially a problem of how females pick males, since females invest more in reproduction, have more to lose, and have to be choosier. Ideally, a female should pick a male for his good genes to pass on to her offspring. Since genes themselves are hard to assess, a female should look for quick indicators of good genes in a male, and a superior male should provide such indicators. In practice, male traits such as plumage, songs, and displays usually serve as indicators. Why do males ‘choose’ to advertise with those particular indicators, why should females trust a male’s honesty and find those indicators attractive, and why do they imply good genes?

  I have described the problem as if a gazelle or courting male voluntarily picks out some indicator from among many possible ones, and as if a lion or a female decides on reflection whether it is really a valid indicator of speed or good genes. In practice, of course, those ‘choices’ are the result of evolution and become specified by genes. Those females who select males on the basis of indicators that really denote good male genes, and those males that use unambiguous indicators of good genes for self-advertisement, tend to leave the most offspring, as do those gazelles and lions that spare themselves unnecessary chases.

  As it turns out, many of the advertising signals evolved by animals pose a paradox similar to that posed by cigarette advertisements. The indicators often seem to be ones that do not suggest speed or good genes but instead constitute handicaps, expenses, or sources of risk. For example, a gazelle’s signal to a lion that it sees approaching consists of a peculiar form of behaviour termed ‘stotting’. Instead of running away as fast as possible, the gazelle runs slowly while repeatedly jumping high into the air with stiff-legged leaps. Why on earth should the gazelle indulge in this seemingly self-destructive display, which wastes time and energy and gives the lion a chance to catch up? Or think of the males of many animal species which sport large structures, such as a peacock’s tail or a bird of paradise’s plumes, that make movement difficult. Males of many more species have bright colours, loud songs, or conspicuous displays that attract predators. Why should a male advertise such an impediment, and why should a female like it? These paradoxes remain an important unsolved problem in animal behaviour today.

  Zahavi’s theory, which remains controversial among biologists, goes to the heart of this paradox. According to his theory, those deleterious structures and forms of behaviour constitute valid indicators that the signalling animal is being honest in its claim of superiority, precisely because those traits themselves impose handicaps. A signal that entails no cost lends itself to cheating, since even a slow or inferior animal can afford to give the signal. Only costly or deleterious signals are guarantees of honesty. For example, a slow gazelle that stotted at an approaching lion would seal its fate, whereas a fast gazelle could still outrun the lion after stotting. By stotting, the gazelle boasts to the lion, ‘I’m so fast that I can escape you even after giving you this head start.’ The lion thereby has grounds for believing in the gazelle’s honesty, and both the lion and the gazelle profit by not wasting time and energy on a chase whose outcome is certain.

  Similarly, as applied to males displaying towards females, Zahavi’s theory reasons that any male that has managed to survive despite the handicap of a big tail or conspicuous song must have terrific genes in other respects. He has proved that he must be especially good at escaping predators, finding food, and resisting disease. The bigger the handicap, the more rigorous the test that he has passed. The female who selects such a male is like the medieval damsel testing her knight suitors by watching them slay dragons. When she sees a one-armed knight who can still slay a dragon, she knows that she has finally found a knight with great genes. That knight, by flaunting his handicap, is actually flaunting his superiority.

  It seems to me that Zahavi’s theory applies to much costly or dangerous human behaviour aimed at achieving status in general or at sexual benefits in particular. For instance, men who woo women with costly gifts and other displays of wealth are in effect saying, ‘I have plenty of money to support you and children, and you can believe my boast because you see how much money I’m spending now without blanching.’ People who show off expensive jewels, sports cars, or works of art gain status because the signal cannot be faked; everyone else knows what those ostentatious objects cost. American Indians of the Pacific Northwest used to seek status by competing to give away as much wealth as possible in ceremonies known as potlatch rituals. In the days before modern medicine, tattooing was not only painful but dangerous because of the risk of infection; hence tattooed people in effect were advertising two facets of their strength, resistance to disease plus tolerance of pain. Men on the Pacific island of Malekula show off by the insanely dangerous practice of building a high tower and jumping off it head first, after tying one end of some stout vines to their ankles and the other end to the top of the tower. The length of the vines is calculated to stop the braggart’s plunge while his head is still a few feet above the ground. Survival guarantees that the jumper is courageous, carefully calculating, and a good builder.

  Zahavi’s theory can also be extended to human abuse of chemicals. Especially in adolescence and early adulthood, the age when drug abuse is most likely to begin, we are devoting much energy to asserting our status. I suggest that we share the same unconscious instinct that leads birds to indulge in dangerous displays. Ten thousand years ago, we ‘displayed’ by challenging a lion or a tribal enemy. Today, we do it in other ways, such as by fast driving or by consuming dangerous drugs.

  The messages of our old and new displays nevertheless remain the same: I’m strong and superior. Even to take drugs only once or twice, I must be strong enough to get past the burning, choking sensation of my first puff on a cigarette, or to get past the misery of my first hangover. To do it chronically and remain alive and healthy, I must be superior (so I imagine). It is a message to our rivals, our peers, our prospective mates – and to ourselves. The smoker’s kiss may taste awful, and the drinker may be impotent in bed, but he or she still hopes to impress peers or attract mates by the implicit message of superiority.

  Alas, the message may be valid for birds, but for us it is a false one. Like so many animal instincts in us, this one has become maladaptive in modern human society. If you can still walk after drinking a bottle of whisky, it may prove that you have high levels of liver alcohol dehydrogenase, but it implies no superiority in other respects. If you have not developed lung cancer after chronically smoking several packs of cigarettes daily, you may have a gene for resist
ance to lung cancer, but that gene does not convey intelligence, business acumen, or the ability to create happiness for your spouse and children.

  It is true that animals with only brief lives and courtships have no alternative except to develop quick indicators, since prospective mates don’t have enough time to measure each other’s real quality. But we, with our long lives and courtships and business associations, have ample time to scrutinize each other’s worth. We need not rely on superficial, misleading indicators. Drug abuse is a classic instance of a once-useful instinct – the reliance on handicap signals – that has turned foul in us. It is that old instinct to which the tobacco and whisky companies are directing their clever, obscene advertisements. If we legalized cocaine, the drug lords too would soon have advertisements appealing to the same instinct. You can easily picture it: the photo of the cowboy on his horse, or the suave man and the attractive maiden, above the tastefully displayed packet of white powder.

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  Now, let’s test my theory by jumping from Western Industrialized Society to the other side of the world. Drug abuse did not begin with the Industrial Revolution. Tobacco was a native American Indian crop, native alcoholic beverages are widespread in the world, and cocaine and opium came to us from other societies. The oldest preserved code of laws, that of the Babylonian king Hammurabi (1792–50 BC), already contained a section regulating drinking houses. Hence my theory, if it is valid, should apply to other societies as well. As an instance of its cross-cultural explanatory power, I shall cite a practice you may not have heard of – kung-fu kerosene drinking.

  I learned of this practice when I was working in Indonesia with a wonderful young biologist named Ardy Irwanto. Ardy and I had come to like and admire each other, and to look out for each other’s well-being. At one point, when we reached a troubled area and I expressed concern about dangerous people we might encounter, Ardy assured me, ‘No problem, Jared. I have kung-fu grade eight.’ He explained that he practised the Oriental martial art of kung-fu and had reached a high level of proficiency, such that he could single-handedly fight off a group of eight attackers. To illustrate, Ardy showed me a scar in his back stemming from an attack by eight ruffians. One had knifed him, whereupon Ardy broke the arms of two and the skull of a third and the remainder fled. I had nothing to fear in Ardy’s company, he told me.

  One evening at our campsite, Ardy walked with his drinking cup up to our jerrycans. As usual, we had two cans: a blue one for water, and a red one for kerosene for our pressure lamp. To my horror, I watched Ardy pour from the red jerrycan and raise the cup to his lips. Remembering an awful moment during a mountaineering expedition when I had taken a sip of kerosene by mistake and spent all the next day coughing it back up, I screamed to Ardy to stop. But he raised his hand and said calmly, ‘No problem, Jared. I have kung-fu grade eight.’

  Ardy explained that kung-fu gave him strength, which he and his fellow kung-fu masters tested each month by drinking a cup of kerosene. Without kung-fu, of course, kerosene would make a weaker person sick. Heaven forbid that I, Jared, for instance, should try it. But it did him, Ardy, no harm, because he had kung-fu. He calmly retired to his tent to sip his kerosene and emerged the next morning, happy and healthy as usual.

  I cannot believe that kerosene did Ardy no harm. I wish that he could have found a less damaging way to make periodic tests of his preparedness. But for him and his kung-fu associates, it served as an indicator of their strength and their advanced level of kung-fu. Only a really robust person could get through that test. Kerosene drinking illustrates the handicap theory of toxic chemical use, in a form as startlingly repellent to us as our cigarettes and alcohol horrified Ardy.

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  In my last example, I shall generalize my theory further by extending its application to the past – in this case, to the civilization of Mayan Indians that flourished in Central America one or two thousand years ago. Archaeologists have been fascinated by Mayan success at creating an advanced society in the middle of tropical rainforest. Many Mayan achievements, such as their calendar, writing, astronomical knowledge, and agricultural practices, are now understood to varying degrees. However, archaeologists were long puzzled by slender tubes of unknown purpose that they kept finding in Mayan excavations.

  The tubes’ function finally became clear with the discovery of painted vases showing scenes of the tubes’ use: to administer intoxicating enemas. The vases depict a high-status figure, evidently a priest or a prince, receiving a ceremonial enema in the presence of other people. The enema tube is shown as connected to a bag of a frothy beer-like beverage–probably containing either alcohol or hallucinogens or both, as suggested by practices of other Indian groups. Many Central and South American Indian tribes formerly practised similar ritual enemas when first encountered by European explorers, and some still do so today. The substances known to be administered range from alcohol (made by fermenting agave sap or a tree bark) to tobacco, peyote, LSD derivatives, and mushroom-derived hallucinogens. Thus, the ritual enema is similar to our consumption of intoxicants by mouth, but there are four reasons why an enema constitutes a more effective and valid indicator of strength than does drinking.

  Firstly, it is possible to relapse into solitary drinking and thus to lose all opportunity for signalling one’s high status to others. However, it is more difficult for a solitary person to administer the same beverage to himself or herself unassisted as an enema. An enema encourages one to enlist associates and thereby automatically creates an occasion for self-advertisement. Secondly, more strength is required to handle alcohol as an enema than as a drink, since the alcohol goes directly into the intestine and thence to the bloodstream, and it is not first diluted with food in the stomach. Thirdly, drugs absorbed from the small intestine after ingestion by mouth pass first to the liver, where many drugs are detoxified before they can reach the brain and other sensitive organs. But drugs absorbed from the rectum after an enema bypass the liver. Finally, nausea may limit one’s intake of drinks but not of enemas. Hence an enema seems to me a more convincing advertisement of superiority than are our whisky advertisements. I recommend this concept to an ambitious public relations firm competing for the account of one of the large distilleries.

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  Let’s now step back and summarize the perspective on chemical abuse that I have suggested. Although frequent self-destruction by chemicals may be unique to humans, I see it as fitting into a broad pattern of animal behaviour and thus as having innumerable animal precedents. All animals have had to evolve signals for quickly communicating messages to other animals. If the signals were ones that any individual animal could master or acquire, they would lend themselves to rampant cheating and hence to disbelief. To be valid and believable, a signal must be one that guarantees the honesty of the signaller, by entailing a cost, risk, or burden that only superior individuals can afford. Many animal signals that would otherwise strike us as counterproductive – such as stotting by gazelles, or costly structures and risky displays with which males court females – can be understood in this light.

  It seems to me that this perspective has contributed to the evolution not only of human art, already discussed in Chapter Nine, but also of human chemical abuse as discussed in this chapter. Both art and chemical abuse are widespread human hallmarks characteristic of most known human societies. Both beg explanation, since it is not immediately obvious why they promote our survival through natural selection, or why they help us acquire mates through sexual selection. I argued in Chapter Nine that art often serves as a valid indicator of an individual’s superiority or status, since art requires skill to create and requires status or wealth to acquire. But those individuals perceived by their fellows as enjoying status thereby acquire enhanced access to resources and mates. I have argued in this chapter that humans seek status through many other costly displays besides art, and that some of those displays (like jumping from towers, fast driving, and chemical abuse) are surprisingly dangerous. The former costl
y displays advertise status or wealth; the latter, dangerous ones advertise that the displaying individual can master even such risks and hence must be superior.

  I do not claim, though, that this perspective affords a total understanding of art or chemical abuse. As I mentioned in Chapter Nine in connection with art, complex patterns of behaviour acquire a life of their own, go far beyond their original purpose (if there ever was just a single purpose), and may even originally have served multiple functions. Just as art is now motivated far more by pleasure than by need for advertisement, chemical abuse too is now clearly much more than an advertisement. It is also a way to get past inhibitions, drown sorrows, or just enjoy a good-tasting drink.

  I also do not deny that, even from an evolutionary perspective, there remains a basic difference between human abuse of chemicals and its animal precedents. Stotting, long tails, and all the animal precedents that I described involve costs, but those forms of behaviour persist because the costs are outweighed by the benefits. A stotting gazelle loses a possible head start in a chase, but gains by decreasing the likelihood that a lion will embark on a serious chase at all. A long-tailed male bird is encumbered in finding food or escaping predators, but those survival disadvantages imposed by natural selection are more than compensated by mating advantages gained through sexual selection. The net balance is more rather than fewer offspring to pass on the male’s genes. These animal traits only appear to be self-destructive; they are actually self-promoting.

  In the case of our chemical abuse, though, the costs outweigh the benefits. Drug addicts and drunkards not only lead shorter lives, but they lose rather than gain attractiveness in the eyes of potential mates and lose the ability to care for children. These traits do not persist because of hidden advantages outweighing costs; they persist mainly because they are chemically addicting. Thus, on balance, they are self-destructive, not self-promoting, patterns of behaviour. While gazelles may occasionally miscalculate in stotting, they do not commit suicide through addiction to the excitement of stotting. In that respect, our self-destructive abuse of chemicals diverged from its animal precursors to become truly a human hallmark.