“All we can really say about asthma is that it is primarily a Western disease,” says Pearce. “There is something about having a Western lifestyle that sets up your immune system in a way that makes you more susceptible. We don’t really understand why.” One suggestion is the hygiene hypothesis—the idea that early exposures to infectious agents strengthen our resistance to asthma and allergies later in life. “It’s a nice theory,” says Pearce, “but it doesn’t completely fit. There are countries like Brazil where asthma rates are high but so are infection rates.”

  The peak age for asthma onset is thirteen, but large numbers of people first experience it in adulthood. “Doctors will tell you that the first few years of life are crucial for asthma, but that’s not exactly true,” says Pearce. “It’s the first few years of exposure. If you change jobs or change countries, you can still get asthma even as an adult.”

  Some years ago, Pearce made a curious discovery—that people who had had a cat early in life seemed to derive lifelong protection from getting asthma. “I like to joke that I’ve studied asthma for thirty years and I have never prevented a single case, but I have saved the lives of a lot of cats,” he says.

  In what way exactly Western lifestyles might provoke asthma isn’t easy to say. Growing up on a farm seems to protect you, and moving to the city increases your risk, but once again we don’t really know why. One intriguing theory, suggested by Thomas Platts-Mills of the University of Virginia, links asthma increases with children spending less time running around outdoors. As Platts-Mills has noted, children used to play outside after school. Now more often than not they go indoors and stay there. “We now have a population that sits around the house and sits still in ways that children have never sat still before,” he told the journal Nature. Children who sit watching television not only are not exercising their lungs as they would if they were at play but even breathe differently from children who are not transfixed by a screen. Specifically, children who are reading take deeper breaths and sigh more often than children watching TV, and that slight difference in respiratory activity may be enough to increase TV watchers’ susceptibility to asthma, according to this theory.

  Other researchers have suggested that viruses may be responsible for asthma onset. A study at the University of British Columbia in 2015 suggested that an absence of four gut microbes (namely, Lachnospira, Veillonella, Faecalibacterium, and Rothia) in infants was closely associated with the development of asthma in the first years of life. But so far all these are just hypotheses. “The bottom line is that we just don’t know yet,” says Pearce.

  III

  ONE OTHER ALL-TOO-COMMON affliction of the lungs deserves a mention, not so much because of what it does to us as because of how extraordinarily long it took us to accept that it was doing it. I refer to smoking and lung cancer.

  It would seem almost impossible to ignore a link between the two. A person who smokes cigarettes regularly (about a pack a day) is fifty times more likely than a nonsmoker to get cancer. In the thirty years between 1920 and 1950, which is when cigarette smoking took off in a big way in the world, the number of lung cancer cases soared. In America, they tripled. Similar increases were noted elsewhere. Yet it took forever to gain consensus that smoking caused lung cancer.

  It seems crazy to us today, but it wasn’t so crazy to people back then. The problem was that huge proportions of people smoked—80 percent of all men by the late 1940s—yet only some of them developed lung cancer. And some people who didn’t smoke also developed lung cancer. So it was not especially straightforward to see a direct link between smoking and cancer. When lots of people are doing something and only some of them are dying from it, it makes it hard to impute blame to a single cause. Some people blamed air pollution for the rise of lung cancer. Others suspected the increased use of asphalt as a paving surface.

  One leading skeptic was Evarts Ambrose Graham (1883–1957), a chest surgeon and professor at Washington University in St. Louis. Graham famously (but facetiously) maintained that we might as plausibly blame lung cancer on the development of nylon stockings because they had become popular at the same time as smoking. But when a student of his, the German-born Ernst Wynder, sought permission to conduct a study on smoking and cancer in the late 1940s, Graham gave his consent, mostly in the expectation that it would disprove the theory of a link between smoking and cancer once and for all. In fact, Wynder demonstrated conclusively that there was a link—so much so that Graham was persuaded by the evidence to change his mind. In 1950, the two men published a joint paper in The Journal of the American Medical Association outlining a clear statistical link between smoking and lung cancer. Soon afterward, the British Medical Journal ran a study with more or less identical findings by Richard Doll and A. Bradford Hill of the London School of Hygiene and Tropical Medicine.*1

  Although two of the world’s most prestigious medical journals had now demonstrated a clear association between smoking and lung cancer, the findings had almost no effect. People just loved smoking too much to quit. Richard Doll in London and Evarts Graham in St. Louis, both lifelong smokers, quit tobacco, but too late in the case of Graham. He died of lung cancer seven years after his own report. Elsewhere smoking just kept rising. The volume of smoking in the United States increased by 20 percent in the 1950s.

  Spurred on by the tobacco industry, many commentators mocked the findings. Because Graham and Wynder could hardly train mice to smoke, they developed a machine that would extract tar from smoked cigarettes, which they then daubed on the skin of laboratory mice, causing tumors to erupt there. A writer from Forbes magazine wondered acidly (and, it must be said, a touch imbecilically), “How many men distill their tar from their tobacco and paint it on their backs?” Governments took little interest in the question. When Britain’s minister of health, Iain Macleod, formally announced at a press conference that there was an unequivocal connection between smoking and lung cancer, he rather undercut his position by smoking conspicuously as he did so.

  The Tobacco Industry Research Committee—a scientific panel paid for by cigarette manufacturers—argued that although cancer from tobacco had been induced in laboratory mice, it had never been demonstrated in humans. “No one has established that cigarette smoke, or any one of its known constituents, is cancer-causing to man,” wrote the panel’s scientific director in 1957, conveniently overlooking that there could never be an ethical way to experimentally induce cancer in a living person.

  To further obviate concerns (and to make their products more appealing to women), cigarette manufacturers introduced filters in the early 1950s. Filters had the great effect that they could claim their cigarettes were now much safer. Most manufacturers charged a premium price for filtered cigarettes, even though the cost of filters was less than the tobacco they displaced. Moreover, most filters didn’t filter out tars and nicotine any better than the tobacco itself had, and to compensate for a perceived loss of taste, the manufacturers started using stronger tobacco. The upshot was that by the late 1950s the average smoker was taking in more tar and nicotine than he had before filters were invented. By this point, the average American adult was smoking four thousand cigarettes a year. Interestingly, quite a lot of valuable cancer research in the 1950s was done by scientists funded by the cigarette industry who were urgently searching for causes of cancer other than cigarettes. As long as tobacco wasn’t directly implicated, their research was often impeccable.

  In 1964, the U.S. surgeon general announced an unequivocal link between smoking and lung cancer, but the announcement had little effect. The number of cigarettes smoked by the average American over the age of sixteen fell slightly from 4,340 a year before the announcement to 4,200 afterward, but then climbed back to about 4,500 and stayed there for years. Remarkably, the American Medical Association took fifteen years to endorse the surgeon general’s finding. Throughout this period, one of the members of the board of the American Cancer Society was a tobacco magnate. As late as 1973, Nature ran an editorial backing women’s smoking during pregnancy on the grounds that it calmed their stress.

  How things have changed. Today just 18 percent of Americans smoke, and it is easy to think that we have pretty much solved the problem. But it’s not quite as simple as that. Nearly one-third of people below the poverty line still smoke, and the habit continues to account for one-fifth of all deaths. It is a problem we are a long way from rectifying.

  * * *

  —

  Finally, let us close on a common breathing affliction that is much less alarming (at least for most of us, most of the time), if no less mysterious: hiccups.

  A hiccup is a sudden spasmodic contraction of the diaphragm, which essentially startles the larynx into closing abruptly, making the famous hic sound. No one knows why they happen. The world record for hiccups appears to have been held by a farmer in northwest Iowa, named Charles Osborne, who hiccuped continuously for sixty-eight years.*2 The hiccups began in 1922 when Osborne tried to lift a 350-pound hog for butchering and somehow triggered a hiccup response. At first he hiccuped about 40 times a minute. Eventually, that slowed to 20 times a minute. Altogether he was estimated to have hiccuped 430 million times over nearly seven decades. He never hiccuped when he was asleep. In the summer of 1990, a year before he died, Osborne’s hiccups abruptly and mysteriously ceased.

  If you do get hiccups and they don’t go away spontaneously after a few minutes, medical science is at a more or less complete loss to help you. The best remedies any doctor can suggest are the same ones you’ve known about since you were small: startling the victims (by sneaking up and going, “Boo!” say), rubbing the back of their neck, having them take a bite of a lemon or a big sip of iced water or pulling on their tongues, and at least a dozen others. Whether any of these age-old remedies actually work is not a matter medical science has addressed. More significantly, no one appears to keep figures on how many people suffer from chronic or sustained hiccuping, but the problem seems not to be trivial. I was told by a surgeon that it happens fairly often after chest surgery—“more often than we like to admit,” he added.

  *1 Hill had already made a signal contribution to medical science. Two years earlier, he had invented the randomized control trial, in a study of the effects of streptomycin.

  *2 Osborne was from the town of Anthon, Iowa. Although the town had a population of only about six hundred people, it was also the home of the tallest person in the world. Bernard Coyne stood over eight feet tall when he died at the age of twenty-three in 1921, just before Osborne began his hiccuping marathon.

  14 FOOD, GLORIOUS FOOD

  Tell me what you eat, and I will tell you what you are.

  —JEAN ANTHELME BRILLAT-SAVARIN, THE PHYSIOLOGY OF TASTE

  WE ALL KNOW that if we consume too much beer and cake and pizza and cheeseburgers and all the other things that make life frankly worth living, we will add pounds to our bodies because we have taken in too many calories. But what exactly are these little numerical oddments that are so keen to make us round and wobbly?

  The calorie is a strange and complicated measure of food energy. Formally, it’s a kilocalorie, and it is defined as the amount of energy required to heat one kilogram of water by one degree centigrade, but it seems safe to say that no one ever thinks of it in those terms when deciding what foods to eat. Just how many calories each of us needs is pretty much a personal matter. Until 1964, the official guidance in the United States was for thirty-two hundred calories per day for a moderately active man and twenty-three hundred for a similarly disposed woman. Today those inputs have been reduced to about twenty-six hundred calories for a moderately active man and two thousand for a moderately active woman. That’s a big reduction. Over the course of a year, for a man that would be almost a quarter of a million fewer calories.

  It probably won’t come as a surprise to hear that in fact the inputs have gone in exactly the other direction. Americans today consume about 25 percent more calories than they did in 1970 (and, let’s face it, we weren’t exactly going without in 1970).

  The father of caloric measurement—indeed of modern food science—was the American academic Wilbur Olin Atwater. A devout and kindly man with a walrus mustache and a stout frame that showed he was no stranger to the larder himself, Atwater was born in 1844 in upstate New York, the son of a traveling Methodist preacher, and studied agricultural chemistry at Wesleyan University in Connecticut. On a study trip to Germany, he was introduced to the exciting new concept of the calorie and returned to America with an evangelical urge to bring scientific rigor to the infant science of nutrition.*1 Taking a position as professor of chemistry at his alma mater, he embarked on a series of experiments to test every aspect of food science. Some of these experiments were a touch unorthodox, not to say risky. In one, he ate a fish poisoned with ptomaine to see what effect it would have on him. The effect was that it nearly killed him.

  Atwater’s most celebrated project was the building of a contraption he called a respiratory calorimeter. This was a sealed chamber, not much larger than a large cupboard, in which subjects were confined for up to five days while Atwater and his helpers minutely measured various facets of their metabolism—inputs of food and oxygen, outputs of carbon dioxide, urea, ammonia, feces, and so on—and so calculated caloric intake. The work was so exacting it took up to sixteen people to read all the dials and perform the calculations. Most of the subjects were students, though the lab janitor, Swede Osterberg, was also sometimes drafted in; quite how voluntarily is unknown. Wesleyan’s president was mystified by the point of the calorimeter—the calorie was an entirely new concept, after all—and especially appalled at the cost, and ordered Atwater to take a 50 percent pay cut or hire an assistant at his own expense. Atwater chose the latter and, undeterred, worked out the calories and nutritional values of practically all known foods—some four thousand in all. In 1896, he produced his magnum opus, The Chemical Composition of American Food Materials, which remained the last word on diet and nutrition for a generation. For a time he was one of the most famous scientists, of any type, in America.

  Much of what Atwater concluded was ultimately wrong, but that wasn’t really his fault. Nobody yet understood the concept of vitamins and minerals or even the need for a balanced diet. To Atwater and his contemporaries, all that made one food superior to another was how well it served as fuel. So he believed that fruits and vegetables provided comparatively little energy and needed to play no part in the average person’s diet. Instead, he suggested that we should eat a lot of meat—two pounds every day, 730 pounds a year. The average American today eats 268 pounds of meat a year, about a third of Atwater’s recommended amount, and most authorities say that is still too much.

  Atwater’s most unsettling discovery—to himself as much as to the world at large—was that alcohol was an especially rich source of calories, and thus an efficient fuel. As the son of a clergyman and a teetotaler himself, he was appalled to report it, but as a diligent scientist he felt his first duty was to the truth, however awkward. In consequence, he was swiftly disowned by his own, devoutly Methodist university and its already scornful president.

  Before the controversy could be resolved, fate intervened. In 1904, Atwater suffered a massive stroke. He lingered for three years without recovering his faculties and died aged sixty-three, but his long efforts secured the calorie’s place at the heart of nutrition science, evidently for all time.

  * * *

  —

  As a measure of dietary intake, the calorie has a number of failings. For one thing, it gives no indication of whether a food is actually good for you or not. The concept of “empty” calories was quite unknown in the early twentieth century. Nor does conventional calorie measurement account for how foods are absorbed as they pass through the body. A great many nuts, for instance, are less completely digested than other foods, which means that they leave behind fewer calories than are consumed. You may eat 170 calories’ worth of almonds, but keep only 130 of them. The other 40 sluice through without, as it were, touching the sides.

  By whatever means you measure it, we are pretty good at extracting energy from food, not because we have an especially dynamic metabolism but because of a trick we learned a very long time ago: cooking. No one knows even approximately when humans first began cooking food. We have good evidence that our ancestors were utilizing fire 300,000 years ago, but Richard Wrangham of Harvard, who has devoted much of his career to studying the matter, believes that our ancestors mastered fire a million and a half years before that—which is to say long before we were properly human.

  Cooking confers all kinds of benefits. It kills toxins, improves taste, makes tough substances chewable, greatly broadens the range of what we can eat, and above all vastly boosts the amount of calories humans can derive from what they eat. It is widely believed now that cooked food gave us the energy to grow big brains and the leisure to put them to use.

  But in order to cook food, you also need to be able to gather and prepare it efficiently, and that is what Daniel Lieberman of Harvard believes is at the heart of our becoming modern. “You can’t possibly have a large brain unless you’ve got the energy to fuel it,” he told me when we met in the autumn of 2018. “And in order to fuel it, you need to master hunting and gathering. That’s more challenging than people realize. It’s not just a question of picking berries or digging up tubers; it is a matter of processing foods—making them easier to eat and digest, and safer to eat—and that involves toolmaking and communication and cooperation. That is the essence of what drove the shift from primitive to modern humans.”