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Self-destructive chemical abuse by humans has precedents in animal displays that are costly or dangerous to the displaying animal. Such behaviour may have originated from the dilemma that signals available to any individual lend themselves to cheating. But costly or dangerous signals carry a built-in guarantee of honesty and are thus usefulas long as their benefits outweigh their costs. Unfortunately, this old evolutionary framework has gone awry in us.

Chernobylformaldehyde in drywallsasbestoslead poisoningsmogthe Valdez oil spillLove CanalAgent Orange Hardly a month goes by without our learning of yet another way in which we and our children have been exposed to toxic chemicals through the negligence of others. The public's outrage, sense of helplessness, and demand for change are growing. Why, then, do we do to ourselves that which we cannot stand for others to do to us? How do we explain the paradox that many people intentionally consume, inject, or inhale toxic chemicals, such as alcohol, cocaine, and the chemicals in tobacco smoke? Why are various forms of this wilful self-damage native to many contemporary societies, from primitive tribes to high-tech urbanites, and extending back into the past as far as we have written records?

Like the subjects of the preceding three chapters, drug abuse is also a hallmark virtually unique to the human species, albeit an evil one rather than a noble one (like language and art) or a mixed blessing (agriculture). is not the worst of our evil hallmarks; it does not threaten the survival of civilization, as do our genocidal tendencies and our environmental destructiveness. But it is still damaging and widespread enough to beg the question of its origins.

The problem is not so much in understanding why we continue to take toxic chemicals once we have started. In part, that is because our drugs of abuse are addictive. Instead, the greater mystery is what impels us to begin at all. Evidence for the damaging or lethal effects of alcohol, cocaine, and tobacco is by now overwhelming and familiar. Only the existence of some strong countervailing motives could explain why people consume these poisons voluntarily, even eagerly. It is as if unconscious programmes were driving us to do something we know to be dangerous. What could those programmes be?

Naturally, there is no single explanation: different motives carry different weight with different people or in different societies. For instance, some people drink to overcome their inhibitions, others to deaden their feelings or drown their sorrows, still others because they like the taste of alcoholic beverages. Naturally, too, differences among human populations and social classes in their options for achieving satisfying lives largely account for geographic and class differences in chemical abuse. It is not surprising that self-destructive alcoholism is a bigger problem in high-unemployment areas of Ireland than in Southeast England, or that cocaine and heroin addiction is commoner in Harlem than in affluent suburbs. Hence it is tempting to dismiss drug abuse as a human hallmark with obvious social and cultural causes, and in no need of a search for animal precedents.

However, none of the motives that I have just mentioned goes to the heart of the paradox of our actively seeking what we know to be harmful. In this chapter I shall propose one other contributing motive which does address that paradox. It relates our chemical self-assaults to a wide range of seemingly self-destructive traits in animals, and to a general theory of animal signalling. It unifies a wide range of phenomena in our culture, from smoking and alcoholism to drug abuse. It has potential cross-cultural validity, for it may explain not just phenomena of the Western world but also some otherwise mystifying customs elsewhere, such as kerosene drinking by Indonesian kung-fu experts. I will also reach into the past and apply the theory to the seemingly bizarre practice of ceremonial enemas in ancient Mayan civilization.

Let me begin by relating how I arrived at this idea. One day, I was abruptly struck by the puzzle that companies manufacturing toxic chemicals for human use advertise their use explicitly. This business practice would seem a sure route to bankruptcy. Yet, while we do not tolerate advertisements for cocaine, advertisements for tobacco and alcohol are so widespread that we cease to regard their existence as puzzling. It hit me only after I had been living with New Guinea hunters in the jungle for many months, far from any advertising.

Day after day, my New Guinea friends had been asking me about Western customs, and I had come to realize through their astonished responses how senseless many of our customs are. Then the months of fieldwork ended with one of those sudden transitions that modern transportation has made possible. On 25 June I was still in the jungle, watching a brilliantly coloured male bird of paradise flap awkwardly across a clearing, dragging its 3-foot-long tail behind it. On 26 June I was sitting in a Boeing 747 jet, reading the magazines and catching up on the wonders of Western civilization.

I leafed through the first magazine. It fell open to a page with a photograph of a tough-looking man on horseback chasing cows, and the name of a brand of cigarette in large letters below. The American in me knew what the photograph was about, but part of me was still in the jungle, looking at that photo naively. Perhaps my reaction will not seem so strange to you if you try to imagine yourself completely unfamiliar with Western society, seeing the advertisement for the first time, and trying to fathom the connection between chasing cows and smoking (or not smoking) cigarettes.

The naive part of me, fresh out of the jungle, thought: such a brilliant anti-smoking ad! It is well known that smoking impairs athletic ability and causes cancer and early death. Cowboys are widely regarded as athletic and admirable. This advertisement must be a devastating new appeal by the anti-smoking forces, telling us that if we smoke that particular brand of cigarette, we will not be fit to be cowboys. What an effective message to our youth!

But then it became obvious that the advertisement had been put there by the cigarette company itself, which somehow hoped that readers would draw exactly the opposite message from the advertisement. How on earth did the company let its public relations department talk it into such a disastrous miscalculation? Surely, that advertisement would dissuade any person concerned about his/her strength and self-image from starting to smoke. Still half immersed in the jungle, I turned to another page. There I saw a photo of a whisky bottle on a table, a man sipping presumably the bottle's contents from a glass, and an obviously fertile young woman gazing at him admiringly as if she were on the verge of sexual surrender. How can that be, I asked myself? Everyone knows that alcohol interferes with sexual function, tends to make men impotent, makes one likely to stumble, impairs judgement, and predisposes to cirrhosis of the liver and other debilitating conditions. In the immortal words of the porter in Shakespeare's Macbeth, 'It [drink] provokes the desire, but it takes away the performance. A man with such handicaps should conceal them at all costs from a woman he aims to seduce. Why is the man in the photograph intentionally displaying those handicaps? Do whisky manufacturers think that pictures of this impaired individual will help sell their product? One could expect that Mothers Against Drunk Driving would be the ones producing such advertisements, and that the whisky companies would be suing to prevent publication.

Page after page of advertisements flaunted the use of cigarettes or strong alcohol, and hinted at their benefits. There were even pictures of young people smoking in the presence of attractive members of the opposite sex, as if to imply that smoking too brought sexual opportunities. Yet any non-smoker who has ever been kissed by (or tried to kiss) a smoker knows how severely the smoker's bad breath compromises his or her sex appeal. The advertisement paradoxically implied not just sexual benefits but also platonic friendships, business opportunities, vigour, health, and happiness, when the direct conclusion to be drawn from the advertisements was actually the reverse.

As the days passed and I reimmersed myself in Western civilization, I gradually stopped noticing its apparently self-defeating advertisements. I retreated into analysing my field data and wondering instead about an entirely different paradox, involving bird evolution. That paradox was what led me finally to understand one rationale behind cigarette and whisky advertisements. The new paradox concerned the reason that male bird of paradise I had been watching on 25 June had evolved the impediment of a tail 3 feet long. Males of other bird of paradise species evolved other bizarre impediments, such as long plumes growing out of their eyebrows, the habit of hanging upside-down, and brilliant colours and loud calls likely to attract hawks. All those features must impair male survival, yet they also serve as the advertisements by which male birds of paradise woo female birds of paradise. Like many other biologists, I found myself wondering why male birds of paradise use such handicaps as advertisements, and why females find the handicaps attractive.

At that point I came across a remarkable paper by an Israeli biologist, Amotz Zahavi, who had conceived a novel general theory about the role of costly or self-destructive signals in animal behaviour. For example, Zahavi attempted to explain how deleterious male traits might attract a female precisely because they constitute handicaps. On reflection, I decided that Zahavi's hypothesis might apply to the birds of paradise I studied. Suddenly I realized, with growing excitement, that his theory perhaps could also be extended to explain the paradox of our use of toxic chemicals, and our touting it in advertisements.

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 f 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 'slotting'. 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 slotted at an approaching lion would seal its fate, whereas a fast gazelle could still outrun the lion after slotting. By slotting, the gazelle boasts lo the lion, 'I'm so fasl that I can escape you even after giving you this head slarl. The lion ihereby has grounds for believing in ihe gazelle's honesty, and both ihe lion and ihe gazelle profit by nol wasling lime and energy on a chase whose outcome is cerlain. Similarly, as applied lo males displaying towards females, Zahavi's iheory reasons lhal any male lhal has managed lo survive despite ihe handicap of a big lail or conspicuous song musl have terrific genes in other respects. He has proved thai he musl be especially good al escaping predalors, finding food, and resisling disease. The bigger ihe handicap, ihe more rigorous ihe lest lhal he has passed. The female who selects such a male is like the medieval damsel testing her knighl suilors by walching ihem slay dragons. When she sees a one-armed knighl who can slill slay a dragon, she knows lhal she has finally found a knighl wilh greal genes. Thai knighl, by flaunting his handicap, is aclually flaunting his superiority.

Il seems lo me lhal Zahavi's iheory applies to much cosily or dangerous human behaviour aimed at achieving stalus in general or al sexual benefils in particular. For inslance, men who woo women wilh cosily gifts and olher displays of weallh are in effecl saying, 'I have plenty of money lo support you and children, and you can believe my boast because you see how much money I'm spending now withoul blanching. People who show off expensive jewels, sports cars, or works of art gain slalus because ihe signal cannol be faked; everyone else knows whal those oslentatious objecls cosl. American Indians of ihe Pacific Norlh-wesl used lo seek slalus by competing lo give away as much weallh as possible in ceremonies known as pollalch riluals. In ihe days before modern medicine, lallooing was not only painful bul dangerous because of ihe risk of infection; hence lallooed people in effecl were advertising two facels of iheir slrenglh, resistance lo disease plus tolerance of pain. Men on ihe Pacific island of Malekula show off by the insanely dangerous practice of building a high tower and jumping off it head first, after lying one end of some sloul vines lo iheir ankles and ihe olher end lo ihe lop of the tower. The length of ihe vines is calculaled to slop ihe braggart's plunge while his head is still a few feel above ihe ground. Survival guaranlees lhal ihe jumper is courageous, carefully calculating, and a good builder. Zahavi's iheory can also be exlended lo human abuse of chemicals. Especially in adolescence and early adullhood, ihe age when drug abuse is mosl likely lo begin, we are devoting much energy to asserting our stalus. I suggesl lhal we share ihe same unconscious inslincl lhal leads birds lo indulge in dangerous displays. Ten ihousand years ago, we 'displayed' by challenging a lion or a Iribal enemy. Today, we do it in olher ways, such as by fast driving or by consuming dangerous drugs.

The messages of our old and new displays nevertheless remain ihe same: I'm strong and superior. Even lo lake drugs only once or Iwice, I musl be slrong enough lo gel pasl ihe burning, choking sensation of my firsl puff on a cigarette, or to gel pasl ihe misery of my firsl hangover. To do ii chronically and remain alive and heallhy, I musl be superior (so I imagine). Il is a message to our rivals, our peers, our prospective malesand lo ourselves. The smoker's kiss may lasle awful, and the drinker may be impotenl in bed, bul he or she slill hopes lo impress peers or allracl mates by the implicil message of superiorily.

Alas, ihe message may be valid for birds, bul for us il 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 thai you have high levels of liver alcohol dehydrogenase, bul il implies no superiority in olher respects. If you have not developed lung cancer after chronically smoking several packs of cigarettes daily, you may have a gene for resistance to lung cancer, but thai gene does nol convey intelligence, business acumen, or the ability to creale 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 instinctthe reliance on handicap signalsthat 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.

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 jerry can 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. In my last example, I shall generalize my theory further by extending its application to the pastin 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 beverageprobably 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. 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 counterproductivesuch as stotting by gazelles, or costly structures and risky displays with which males court femalescan 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 costly 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.