A Natural History of the Senses

by Diane Ackerman

  THE BLOOM OF A TASTE BUD

  Seen by scanning electron microscope, our taste buds look as huge as volcanoes on Mars, while those of a shark are beautiful mounds of pastel-colored tissue paper—until we remember what they’re used for. In reality, taste buds are exceedingly small. Adults have about 10,000, grouped by theme (salt, sour, sweet, bitter), at various sites in the mouth. Inside each one, about fifty taste cells busily relay information to a neuron, which will alert the brain. Not much tasting happens in the center of the tongue, but there are also incidental taste buds on the palate, pharynx, and tonsils, which cling like bats to the damp, slimy limestone walls of a cave. Rabbits have 17,000 taste buds, parrots only about 400, cows 25,000. What are they tasting? Maybe a cow needs that many to enjoy a relentless diet of grass.

  At the tip of the tongue, we taste sweet things; bitter things at the back; sour things at the sides; and salty things spread over the surface, but mainly up front. The tongue is like a kingdom divided into principalities according to sensory talent. It would be as if all those who could see lived to the east, those who could hear lived to the west, those who could taste lived to the south, and those who could touch lived to the north. A flavor traveling through this kingdom is not recognized in the same way in any two places. If we lick an ice cream cone, a lollipop, or a cake-batter-covered finger, we touch the food with the tip of the tongue, where the taste buds for sweetness are, and it gives us an extra jolt of pleasure. A cube of sugar under the tongue won’t taste as sweet as one placed on the tongue. Our threshold for bitter is the lowest. Because the taste buds for bitter lie at the back of the tongue; as a final defense against danger they can make us gag to keep a substance from sliding down the throat. Some people do, in fact, gag when they take quinine, or drink coffee for the first time, or try olives. Our taste buds can detect sweetness in something even if only one part in two hundred is sweet. Butterflies and blowflies, which have most of their taste organs on their front feet, need only step in a sweet solution to taste it. Dogs, horses, and many other animals have a sweet tooth, as we do. We can detect saltiness in one part in 400, sourness in one part in 130,000, but bitterness in as little as one part in 2,000,000. Nor is it necessary for us to recognize poisonous things as tasting different from one another; they just taste bitter. Distinguishing between bitter and sweet substances is so essential to our lives that it has burst through our language. Children, joy, a trusted friend, a lover all are referred to as “sweet.” Regret, an enemy, pain, disappointment, a nasty argument all are referred to as “bitter.” The “bitter pill” we metaphorically dread is likely to be poison.

  Taste buds got their name from the nineteenth-century German scientists Georg Meissner and Rudolf Wagner, who discovered mounds made up of taste cells that overlap like petals. Taste buds wear out every week to ten days, and we replace them, although not as frequently over the age of forty-five—our palates really do become jaded* as we get older. It takes a more intense taste to produce the same level of sensation, and children have the keenest sense of taste. A baby’s mouth has many more taste buds than an adult’s, with some even dotting the cheeks. Children adore sweets partly because the tips of their tongues, more sensitive to sugar, haven’t yet been blunted by years of gourmandizing or trying to eat hot soup before it cools. A person born without a tongue, or who has had his tongue cut out, still can taste. Brillat-Savarin tells of a Frenchman in Algeria who was punished for an attempted prison escape by having “the forepart of his tongue … cut off clear to the ligament.” Swallowing was difficult and tiring for him, although he could still taste fairly well, “but very sour or bitter things caused him unbearable pain.”

  Just as we can smell something only when it begins to evaporate, we can taste something only when it begins to dissolve, and we cannot do that without saliva. Every taste we can imagine—from mangoes to hundred-year-old eggs—comes from a combination of the four primary tastes plus one or two others. And yet we can distinguish between tastes with finesse, as wine-, tea-, cheese- and other professional tasters do. The Greeks and Romans, who were sophisticated about fish, could tell just by tasting one what waters it came from. As precise as our sense of taste is, illusions can still surprise us. For example, MSG doesn’t taste saltier than table salt, but it really contains much more sodium. One of its ingredients, glutamate, blocks our ability to taste it as salty. A neurologist at the Albert Einstein College of Medicine once tested the amount of MSG in a bowl of wonton soup in a Chinese restaurant in Manhattan, and he found 7.5 grams of MSG, as much sodium as one should limit oneself to in an entire day.

  After brushing our teeth in the morning, orange juice tastes bitter. Why? Because our taste buds have membranes that contain fatlike phospholipids, and toothpastes contains a detergent that breaks down fat and grease. So the toothpaste first assaults the membranes with its detergent, leaving them raw; then chemicals in the toothpaste, such as formaldehyde, chalk, and saccharin, cause a sour taste when they mix with the citric and ascorbic acids of orange juice. Chewing the leaves of the asclepiad (a relative of the milkweed) makes one’s ability to taste sweetness vanish. Sugar would taste bland and gritty. When Africans chew a berry they call “miraculous fruit,” it becomes impossible to taste anything sour: lemons taste sweet, sour wine tastes sweet, rhubarb tastes sweet. Anything off-puttingly sour suddenly becomes delicious. A weak enough solution of salt tastes sweet to us, and some people salt melons to enhance the sweet flavor. Lead and beryllium salts can taste treacherously sweet, even though they’re poisonous and we ought to be tasting them as bitter.

  No two of us taste the same plum. Heredity allows some people to eat asparagus and pee fragrantly afterward (as Proust describes in Remembrance of Things Past), or eat artichokes and then taste any drink, even water, as sweet. Some people are more sensitive to bitter tastes than others and find saccharin appalling, while others guzzle diet sodas. Salt cravers have saltier saliva. Their mouths are accustomed to a higher sodium level, and foods must be saltier before they register as salty. Of course, everyone’s saliva is different and distinctive, flavored by diet, whether or not they smoke, heredity, perhaps even mood.

  How strange that we acquire tastes as we grow. Babies don’t like olives, mustard, hot pepper, beer, fruits that make one pucker, or coffee. After all, coffee is bitter, a flavor from the forbidden and dangerous realm. To eat a pickle, one risks one’s common sense, overrides the body’s warning with sheer reason. Calm down, it’s not dangerous, the brain says, it’s novel and interesting, a change, an exhilaration.

  Smell contributes grandly to taste. Without smell, wine would still dizzy and lull us, but much of its captivation would be gone. We often smell something before we taste it, and that’s enough to make us salivate. Smell and taste share a common airshaft, like residents in a high rise who know which is curry, lasagna, or Cajun night for their neighbors. When something lingers in the mouth, we can smell it, and when we inhale a bitter substance—a nasal decongestant, for example—we often taste it as a brassiness at the back of the throat. Smell hits us faster: It takes 25,000 times more molecules of cherry pie to taste it than to smell it. A head cold, by inhibiting smell, smothers taste.

  We normally chew about a hundred times a minute. But, if we let something linger in our mouth, feel its texture, smell its bouquet, roll it around on the tongue, then chew it slowly so that we can hear its echoes, what we’re really doing is savoring it, using several senses in a gustatory free-for-all. A food’s flavor includes its texture, smell, temperature, color, and painfulness (as in spices), among many other features. Creatures of sound, we like some foods to titillate our hearing more than others. There’s a gratifying crunch to a fresh carrot stick, a seductive sizzle to a broiling steak, a rumbling frenzy to soup coming to a boil, an arousing bunching and snapping to a bowl of breakfast cereal. “Food engineers,” wizards of subtle persuasion, create products to assault as many of our senses as possible. Committees put a lot of thought into the design of fast foods. A
s David Bodanis points out with such good humor in The Secret House, potato chips are:

  an example of total destruction foods. The wild attack on the plastic wrap, the slashing and tearing you have to go through is exactly what the manufacturers wish. For the thing about crisp foods is that they’re louder than non-crisp ones.… Destructo-packaging sets a favorable mood.… Crisp foods have to be loud in the upper register. They have to produce a high-frequency shattering; foods which generate low-frequency rumblings are crunchy, or slurpy but not crisp.…

  Companies design potato chips to be too large to fit into the mouth, because in order to hear the high-frequency crackling you need to keep your mouth open. Chips are 80 percent air, and each time we bite one we break open the air-packed cells of the chip, making that noise we call “crispy.” Bodanis asks:

  How to get sufficiently rigid cell walls to twang at these squeaking harmonics? Starch them. The starch granules in potatoes are identical to the starch in stiff shirt collars … whitewash … is … near identical in chemical composition.… All chips are soaked in fat.… So it’s a shrapnel of flying starch and fat that produces the conical air-pressure wave when our determined chip-muncher finally gets to finish her chomp.

  These are high-tech potato chips, of course. The original potato chip was invented in 1853 by George Crum, a chef at Moon Lake Lodge in Saratoga Springs, New York, who became so angry when a guest demanded thinner and thinner French fries that he sliced them laughably thin (he thought) and fried them until they were varnish-brown. The guest loved them, envious fellow guests requested them, word spread, and ultimately Crum started up his own restaurant, which specialized in potato chips.

  The mouth is what keeps the prison of our bodies sealed up tight. Nothing enters for help or harm without passing through the mouth, which is why it was such an early development in evolution. Every slug, insect, and higher animal has a mouth. Even one-celled animals like paramecia have mouths, and the mouth appears immediately in human embryos. The mouth is more than just the beginning of the long pipeline to the anus: It’s the door to the body, the place where we greet the world, the parlor of great risk. We use our mouths for other things—language, if we’re human; drilling tree bark if we’re a woodpecker; sucking blood if we’re a mosquito—but the mouth mainly holds the tongue, a thick mucous slab of muscle, wearing minute cleats as if it were an athlete.

  THE ULTIMATE DINNER PARTY

  Romans adored the voluptuous feel of food: the sting of pepper, the pleasure-pain of sweet-and-sour dishes, the smoldery sexiness of curries, the piquancy of delicate and rare animals, whose exotic lives they could contemplate as they devoured them, sauces that reminded them of the smells and tastes of lovemaking. It was a time of fabulous, fattening wealth and dangerous, killing poverty. The poor served the wealthy, and could be beaten for a careless word, destroyed for amusement. Among the wealthy, boredom visited like an impossible in-law, whom they devoted most of their lives to entertaining. Orgies and dinner parties were the main diversions, and the Romans amused themselves with the lavishness of a people completely untainted by annoying notions of guilt. In their culture, pleasure glistened as a good in itself, a positive achievement, nothing to repent. Epicurus spoke for a whole society when he asked:

  Is man then meant to spurn the gifts of Nature? Has he been born but to pluck the bitterest fruits? For whom do those flowers grow, that the gods make flourish at mere mortals’ feet?… It is a way of pleasing Providence to give ourselves up to the various delights which she suggests to us; our very needs spring from her laws, and our desires from her inspirations.

  Fighting the enemy, boredom, Romans staged all-night dinner parties and vied with one another in the creation of unusual and ingenious dishes. At one dinner a host served progressively smaller members of the food chain stuffed inside each another: Inside a calf, there was a pig, inside the pig a lamb, inside the lamb a chicken, inside the chicken a rabbit, inside the rabbit a dormouse, and so on. Another host served a variety of dishes that looked different but were all made from the same ingredient. Theme parties were popular, and might include a sort of treasure hunt, where guests who located the peacock brains or flamingo tongues received a prize. Mechanical devices might lower acrobats from the ceiling along with the next course, or send in a plate of lamprey milt on an eel-shaped trolley. Slaves brought garlands of flowers to drape over the diners, and rubbed their bodies with perfumed ungents to relax them. The floor might be knee-deep in rose petals. Course after course would appear, some with peppery sauces to spark the taste buds, others in velvety sauces to soothe them. Slaves blew exotic scents through pipes into the room, and sprinkled the diners with heavy, musky animal perfumes like civet and ambergris. Sometimes the food itself squirted saffron or rose water or some other delicacy into the diner’s face, or birds flew out of it, or it turned out to be inedible (because it was pure gold). The Romans were devotees of what the Germans call Schadenfreude, taking exquisite pleasure in the misfortune of someone else. They loved to surround themselves with midgets, and handicapped and deformed people, who were made to perform sexually or cabaret-style at the parties. Caligula used to have gladiators get right up on the dinner table to fight, splashing the diners with blood and gore. Not all Romans were sadists, but numbers of the wealthy class and many of the emperors were, and they could own, torture, maltreat, or murder their slaves as much as they wished. At least one high-society Roman is recorded to have fattened his eels on the flesh of his slaves. Small wonder Christianity arose as a slave-class movement, emphasizing self-denial, restraint, the poor inheriting the earth, a rich and free life after death, and the ultimate punishment of the luxury-loving rich in the eternal tortures of hell. As Philippa Pullar observes in Consuming Passions, it was from this “class-consciousness and a pride in poverty and simplicity the hatred of the body was born.… All agreeable sensations were damned, all harmonies of taste and smell, sound, sight and feel, the candidate for heaven must resist them all. Pleasure was synonymous with guilt, it was synonymous with Hell.… ‘Let your companions be women pale and thin with fasting,’ instructed Jerome.” Or, as Gibbon put it, “every sensation that is offensive to man was thought acceptable to God.” So the denial of the senses became part of a Christian creed of salvation. The Shakers would later create their stark wooden benches, chairs, and simple boxes in such a mood, but what would they make now of the voluptuousness with which people enjoy Shaker pieces, not as a simple necessity but extravagantly, as art, as an expensive excess bought for the foyer or country house? The word “vicarious” hinges on “vicar,” God’s consul in the outlands, who lived like an island in life’s racy current, delicate, exempt, and unflappable, while babies grew out of wedlock and bulls died, crops shriveled up like pokers or were flooded, and local duennas held musicales for vicar, matrons, and spicy young women (riper than the saintliest mettle could bear). No wonder they lived vicariously; giving pause, giving aid, and, sometimes, giving in to embolisms, dietary manias, and sin. Puritanism denounced spices as too sexually arousing; then the Quakers entered the scene, making all luxury taboo, and soon enough there were revolts against these revolts. Food has always been associated with cycles of sexuality, moral abandon, moral restraint, and a return to sexuality once again—but no one did so with as much flagrant gusto as the ancient Romans.

  Quite possibly the Roman empire fell because of lead poisoning, which can cause miscarriages, infertility, a host of illnesses, and insanity. Lead suffused the Romans’ lives—not only did their water pipes, cooking pots, and jars contain it, but also their cosmetics. But before it did poison them, they staged some of the wildest and most extravagant dinner parties ever known, where people dined lying down, two, three, or more to a couch. While saucy Roman poets like Catullus wrote rigorously sexy poems about affairs with either sex, Ovid wrote charming ones about his robust love of women, how they tormented his soul, and about the roller coaster of flirtation he observed at dinner parties. “Offered a sexless heaven,” he wrote
, “I’d say no thank you, women are such sweet hell.” In one of his poems, he cautions his mistress that, since they’ve both been invited to the same dinner, he’s bound to see her there with her husband. Don’t let him kiss you on the neck, Ovid tells her, it will drive me crazy.

  MACABRE MEALS

  When the chic, sophisticated Romans conquered the wilds of Britain, their cuisine conquered, too. As Pullar has pointed out, the Anglo-Saxon words “cook” and “kitchen” derive from the Latin, so the Romans no doubt greatly raised the level of sophistication in both spheres. Medieval tastes were still Roman tastes (sweet and sour sauces, spicy, currylike dishes). It was the crusaders who developed a taste for the spices of the East—cinnamon, nutmeg, cardamom, mace, cloves, and rose attar—as they had for the perfumes, silks, dyes, ornate sexual practices, and other delicacies. The poor Britains lived in squalor and the rich lived in ostentation, holding magnificent feasts in honor of marriages and other celebrations. Many people have written that medieval cooks used a heavy hand with spices to mask the odor of their half-decayed meat, but ladling on the spices was a legacy from the Romans and the crusaders.

  Some of the strangest culinary habits arose in England during the eighteenth century, when bored city dwellers became fascinated by sadism, sorcery, and a dungeons-and-skeletons sense of fun. The idea arose that torturing an animal made its meat healthier and better tasting and even though Pope, Lamb, and others wrote about the practice with disgust, people indulged in ghoulish preparations that turned their kitchens into charnel houses. They chopped up live fish, which they claimed made the flesh firmer; they tortured bulls before killing them, because they said the meat would otherwise be unhealthy; they tenderized pigs and calves by whipping them to death with knotted ropes; they hung poultry upside down and slowly bled them to death; they skinned living animals. Recipe openers from the era said such things as: “Take a red cock that is not too old and beat him to death.…” This was all sponsored by the peculiar notion that the taste of animal flesh could be improved if the poor thing were put through hell first. Dr. William Kitchiner, in The Cook’s Oracle, cites a grotesque recipe, by a cook named Mizald, for preparing and eating a goose while it is still alive: