Don't Look, Don't Touch, Don't Eat: The Science Behind Revulsion

by Valerie Curtis

  David Tolin at Yale University demonstrated this “law of contagion” in a study using pencils and toilet bowls. He rubbed a pencil around a (clean) toilet bowl and then asked people to rate how aversive they found it. He then took another pencil, touched it to the first one and again asked how aversive it was. Taking the second pencil, he touched it to a third, and so on, up to pencil number 10. He found that for “normal” people the aversive effect fell off rapidly and had disappeared by the fourth or fifth pencil. For people suffering from OCD, however, the chain of contagion persisted; even the twelfth pencil was still contaminated. He describes the world of the OCD patient as being one of “looming waves of spreading contamination.”27 For the unfortunate sufferers, it seems that the law of contagion has gone into overdrive; even the slightest suggestion of taint spreads to every possible contact and hardly ever fades. Their perception of contagion can become so pervasive that it makes normal life impossible.

  Culture: The Collective Brain

  We all come equipped with high, medium, or low disgust settings, and different sensitivities to different kinds of disgust; life also tunes our system up or down according to how much we need it at the time, and according to our experience of encountering and learning about disgusting stuff. This is all very clever of our brains. But, smart as this is, we humans have an even better way of learning to be disgusted. One reason for our rampant success as a species is that we are more than just individuals; we are also wired into a collective brain. This hive brain is a fantastic repository of information, providing cultural maps that we use to navigate the dangers of hidden pathogens.

  How does living in a collective brain affect our disgust sensibilities? And how far can culture influence those sensibilities? And to take us back to our castaways: Could the practice of cannibalism ever be so socially acceptable that we could all become cannibals? Could there even be cultures where the Medusa story would fail to elicit shock and disgust?

  Individual brains affect the content of culture, and culture affects individual brains. While the collective culture of any one society reflects the psychological makeup of the individuals contained within it, it also reflects the shared experiences of those individuals and it reflects those ideas that people have found most profitable to pass on. More controversially, the collective culture of a group may also reflect a past history of being selected for as a group.28 This can happen, at least in theory, when cultural ideas confer on groups the qualities that make them more successful and persistent than their competitor groups.29

  Different groups have different cultures—as a result of their different experiences—and it is technically possible that there may be genetic differences in the underlying psychology of different groups. Imagine, for example, a population beset by famine. A small proportion of that population, by chance, were less disgusted by cannibalism. Those individuals survived the period of scarcity by eating the dead and dying. A population squeezed through such a genetic bottleneck would tend, on average, to have a lower disgust threshold and so be more predisposed to eating human flesh than neighbors who had not had the same experience. Whether that group would retain any distinctive genetic psychological differences would depend on the strength of the selection pressure and on the amount of population mixing after the famine event. A similar argument applies to disease. One society’s constituent individuals could be more genetically disgust sensitive than another’s because of a previous water- or louse-borne epidemic that led to the differential survival of the society’s most fastidious individuals.

  This is straightforward individual selection producing a change in the genetic makeup of the group. But now imagine a people who, for some reason, invented a mortuary rite that involved honoring the bodies of deceased elders by offering around small portions of their brains in a public ceremony. Imagine that this ceremony was shocking and powerful, and created a feeling of closeness among brethren, of social continuity, of family values, and of cohesion. Imagine then that such people had a competition over land with a neighboring tribe with no such ideology. Who would win, all else being equal? Clearly our cephalophagous group with its tighter social structure should have an advantage. The brain-tasting cultural ideology could then spread though conquest. This might help explain the persistence of the mortuary practices of the Fore people of Papua New Guinea, which continued for hundreds of years, despite being the cause of kuru—a degenerative brain disease contracted through the consumption of brain tissue.30

  Now imagine a small sect that invents a ritual that involves pretending to eat the flesh and drink the blood of their leader. The rite is, again, emotionally “sticky,” involving a collective experience of transgression, of overcoming disgust together, binding the celebrants into a tight brotherhood, with shared emotional memories. The brotherhood of the shared rite builds confidence and strengthens armies to conquer. The human tendency to follow charismatic leadership, and to blindly copy one another, does the rest. Conquest and evangelism spread the cannibalistic rite and the brotherhood across time and space, till Christianity becomes the dominant culture of the West and much of the rest of the world. (The substitution of bread and wine for real body bits removed the disease risk downside, of course.) There is some evidence that it was not just the ideas of Christianity that spread, but that, helped by such ideas, the genes of the Christians spread too.31

  During the recent Liberian civil war, boy soldiers were reported roasting and eating human flesh. Acts of depravity serve to terrify enemies and to create a bond of brotherhood between members of a fighting band. Our own children can similarly indulge in World of Warcraft. The game currently has twelve million subscribers; players can choose to play as a race of zombies, called the Forsaken, which have a “spell” that allows the character to cannibalize corpses. In the equally popular Grand Theft Auto, media tycoon Donald Love has Toni Cipriani kill Avery Carrington and bring him to his private jet in order to eat him on the trip.32

  All people, not just computer gamers, love to experiment with objects and ideas to learn how they work and what they do. Such “play” activity is generally accomplished in a safe environment, with a pretend object (a doll, a fairground ride), or in imagination, in a story (folktale, novel, movie, or computer game, for example). Emotional responses to simulated risks or experiences still get recorded as mental “Post-its” on objects or ideas, and they are then available to be called up when needed “for real.” The profits to be made in the cannibalism industry—whether from books about Jeffrey Dahmer or Hannibal Lecter, from movies about zombies, from computer games, or indeed from the sales receipts for tickets to see Géricault’s picture of the raft of the Medusa when it was exhibited in London—testify to the fact that “play” cannibalism is alive and well in Western culture.

  But this evidence of cannibalism around us still hasn’t proven that culture can make cannibalism an acceptable and normal part of social activity. We’ve seen examples of desperate cannibalism, deviant cannibalism, ritual cannibalism, and play cannibalism, but were there ever any societies where cannibalism was “normal”? Where cannibalism was practiced just for the sake of nutrition? Gastronomic cannibalism, as it were?

  There are plenty of historical accounts, but it is very hard to find any solid evidence of normal, everyday, culturally sanctioned cannibalism. Though the historical literature is full of colorful tales of the cannibal tribes of Africa, the Indies, and the Caribbean (the Caribs gave their name to cannibalism), a closer look reveals how unreliable the accounts are. The typical report of cannibalism goes like this: “Our disgusting next-door neighbors are uncivilized savages, their women like nothing better than roasted baby, or boiled-up visitor, and they sleep around too.” Or like this: “Tribe X were uncivilized savages who went around eating each other until we [insert name of colonial power] brought them order and civilization.” In William Arens’s investigation for his book The Man-Eating Myth, he found no reliable firsthand accounts of “everyday” cannibalism. He concluded that cann
ibal tales are just that—tales told by individuals keen to blacken the reputation of the despised enemy.33 These are then faithfully recorded by the credulous anthropologist, wanting to believe the best of “his” pet tribe, and ill of its enemies.

  Travelers also have a vested interest in being credulous, since shock-horror sells travelers’ tales. Missionaries and colonists, too, have a motive for suspending their disbelief, since the worse the habits of the dreadful savages, the better the job they can claim to have done in bringing them to civilization. The flesh markets of eighteenth-century Fiji were probably a myth, and the Korowai of today’s eastern Papua eat human flesh only in special circumstances. The archaeological record is similarly equivocal about cannibalism; cut marks on bones and heat-altered human remains have been found in many sites but can be interpreted in various ways.34 The best evidence for the consumption of human flesh comes from the discovery of the human protein myoglobin in cooking pots and in feces in one hastily abandoned Pueblo Indian site in Colorado from AD 1150. But the fact that seven individuals were dismembered and eaten during, or soon after, the evacuation of the site again suggests drastic circumstances, not habitual flesh eating.35 Cannibalism may only ever have been an act of deviance, a means to shock or to reinforce a ritual, or in desperation in times of famine—as in biblical Samaria or on the raft of the Medusa.

  The ordinary, everyday consumption of other people for food has probably always been found disgusting, showing the limits to what can become a normal part of human culture. Cannibalism does, however, nicely illustrate the diversity of our disgust responses. They can be naturally strong or weak, they can be modified by experience, they can be suppressed—in extremis, they can be toyed with, and they can be elicited in powerful social rituals that shock and bind. Disgust is an adaptive system, standard equipment for humans (and all animals, as I have argued), whose basic themes around disease avoidance allow a degree of variation.36 The disgust system is not infinitely elastic, however; we can never get rid of the ancestral voices in our heads that say, “Don’t touch! Don’t eat!” and call out alarms whenever infection cues, like the opportunity to consume human flesh, are detected.

  CHAPTER FOUR

  MANER MAYKS MAN

  Manners are of more importance than laws. . . . Manners are what vex or soothe, corrupt or purify, exalt or debase, barbarize or refine us, by a constant, steady, uniform, insensible operation, like that of the air we breathe in.

  Edmund Burke, Letters on a Regicide Peace

  Imagine a world without manners. Getting up in the morning, your partner burps and drags on a grubby dressing gown. You can’t find your toothbrush so you use his, and then wipe some muck off the bathroom floor with it. Downstairs, your daughter gives you a big dribbling kiss and then sits picking her nose at the breakfast table, wiping her fingers on the chair cushion. You select the least filthy plate from last night’s pile and slop leftover curry onto it. Everyone grabs for the best bits, even before you can get it on the table, and the little one goes hungry again. On the way to work, you step over the large turd deposited by a neighbor on your front path and then drive into a jam caused by everyone ignoring the traffic lights. In your open-plan office, it’s hard to concentrate for the flies and the smell coming from the rubbish pile in the corner, which has been used as a toilet by someone. You are distracted by a colleague recounting last night’s sexual exploits over the phone in a loud voice. Your boss stands so close to you that you see the crud accumulated in his eyes and are overpowered by the smell of his unwashed armpits. Suddenly hungry, you reach over and grab your colleague’s half-eaten sandwich, which you munch with your mouth open. In the conference room, everyone talks at once until a spitting match breaks out. Leaving work, the strangers in the elevator press up close to you, and one sneezes in your face. Home that evening, you slip in some grease that has been dripped on the kitchen floor; the kids have a farting competition while squabbling over the TV remote. Suddenly you can’t bear it any longer, and it’s time that everybody learned some manners!

  Somehow all that is good about life is missing. Here there is no love, no caring, no respect, no community, no beauty, no quality of life. Without good manners, life hardly seems worth living. Yet manners are so ingrained in our lives that we hardly notice them.

  Though there are plenty of self-help books on etiquette, explaining how to behave at a party, write a thank-you letter, or use table utensils in a foreign country, as well as tracts about how one should behave, such as Stephen L. Carter’s book on civility,1 few behavioral scientists have written about manners.2 So where do manners come from, and what is their relationship with disgust?

  One of the hottest topics in evolutionary biology is the question of what makes us human: what is it that makes us different from other animals? Some argue for language, others for tool use, others that fire allowed us to cook food to fuel big brains;3 others suggest “theory of mind.”4 Undoubtedly, something important happened in the “great leap forward” about fifty thousand years ago that saw the change to truly modern humans with their ratchet of inventiveness, their cumulative shared culture, and their extraordinary ability to extract resources from the environment through cooperative enterprise.5 For me, manners are a prime candidate for the key factor that distinguishes us from animals, one of the fundamental building blocks of what it takes to be a Homo sapiens. An old saw says, “Maner mayks Man.” The acquisition of manners was the first baby step we humans took on the road to large-scale cooperation, and cooperation, underpinned by our moral sense, was the great leap forward that allowed humans to become a hypersocial species, a species that figured out how to work together and so to dominate our planet. So if we want to understand our modern world and the morality that makes it possible, we should start with manners, what the French call la petite morale.

  Keep Your Distance

  Looking at it from my perspective, when I meet you in person, I can respond in one of several adaptive ways. I can approach you and be friendly, signal that I mean well, and cooperate with you. On the other hand, it might be a lot better for me if I walked away, because you are a walking bag of microbes. With every exhalation, you might be emitting billions of influenza viruses or millions of plague bacilli; with every handshake, you might provide hundreds of salmonella bacteria or cholera bacilli; with your friendly embrace, you might be donating a dose of diphtheria or sharing scores of your scabies mites. Your immediate area might be full of your wastes, containing fungus from your fallen hairs or intestinal worms from your feces. If I wanted to get more intimate with you, I might contract hepatitis, syphilis, or worse. Proximity is potentially deadly.

  Yet at the same time, you are a source of value to me. You may have objects to trade, gossip to exchange, social networks to tap into, or good genes to share. If I want to profit from associating with you, I have to take a measured risk—that these positive benefits will outweigh the negative costs of possibly catching something infectious. So I have to make a difficult trade-off calculation: shall I approach you or avoid you? And you too, of course, have to make the same calculation (albeit subconsciously), because to you I am a walking bag of human-adapted parasites that are looking for an opportunity to transmit themselves to you. So how do we get around this problem? How do we maximize our chances of getting the most out of our social contacts, while limiting the risk of catching something nasty?

  Let’s try another thought experiment. Let’s say you have invited an old friend to stay the night. What do you do to minimize disease transmission between you while keeping your relationship friendly?

  The day your friend is due, you tidy the house, picking up unwashed underwear from floors and clearing away used tissues from the sofa, thus removing niches where microbial parasites might be lurking or breeding. You make a particular effort to scrub the bathroom and kitchen, where the sparkling tiles and shined taps display their freedom from bodily fluids. You vacuum up fallen skin cells, crumbs, and organic wastes from the carpet and put fresh lin
en on the bed, reducing the chance that she’ll be bitten by one of your family’s bedbugs or fleas. The white towel you place on her chair has been laundered clean of all traces of the family’s bodily fluids, and a vase of lavender from the garden scents the air, masking the slight stale odor emanating from the microbial decay of the old mattress under the clean sheets. You brush your hair to signal that you groom carefully and have no ectoparasites, and pull on a dirt—and hence parasite—free blouse. You greet your friend with a warm hug, demonstrating that she is so valuable to you that you are prepared to run the risk of contracting one of her viral infections. With impeccable manners, she offers to take off her shoes, so as not to bring environmental pathogens into the house. With impeccable manners, in return, you say, “Don’t bother,” again to demonstrate that she is of more value to you than the state of your carpets.

  You lay the table for dinner so that everyone sits as far apart as possible, to minimize the chances of sharing bodily emanations, and you give the wineglasses a special polish to make sure that there’s no trace of saliva left on them. You are careful to serve potatoes to her with a clean fork, not the one that you’ve coated with microbes from your tongue. Though the dish is unfamiliar, your guest suppresses the desire to sniff at it, to check for fungal decay, showing that she is prepared to take a risk for the sake of your friendship. You remark that the coq au vin is a recipe that you learned from your mother, conveying covert reassurance that you know how to prepare food safely, according to the wisdom of your ancestors. Before dessert you carefully decant the cream from its tub with the out-of-date sell-by label into a pretty serving jug for the dessert. She chews her tart politely, with her mouth closed, so you don’t have to catch any sprays of saliva or look into, and so think about, her microbe-filled cavities. She compliments you on your cooking and then jumps up to help clear the plates, politely offering to wash up. She helps you remove the saliva-contaminated food leftovers while you share the latest gossip over the kitchen sink.