The Skeptics Society & Skeptic magazine

“Nothing in biology makes sense except in the light of evolution.” —Theodosius Dobzhansky

Why can one person smoke and drink heavily into their 90s while another dies from cancer in their 40s? Why are we fat? Why does a suntan look and feel so good if it is bad for us? Why is alternative medicine so popular? Do vaccines work and are they safe? Do toxins in our food cause cancer?

In this article I outline the emerging field of Evolutionary Medicine, looking at how our Stone Age ancestors lived, got sick, and got well over millions of years, and pointing to how we can live longer, healthier, and happier lives today.

As a skeptic, I have learned to often question ideas that are accepted as “common knowledge.” As a physician, I know that some of the drugs and treatments that we are encouraged to use today are only marginally useful at times and sometimes even toxic. Where does evolution come in? I have found that applying evolutionary thinking to common medical knowledge can provide us with fresh insight into the cause and cure of common diseases.

Evolutionary medicine draws insights from three areas of scientific research: (1) archaeologists’ ongoing discoveries about the lives of our paleolithic ancestors; (2) anthropologists’ observations of modern humans living in cultures that have changed little since the Stone Age; and (3) findings of molecular geneticists that have unraveled the story told by our DNA.

These studies have led to fundamental changes in our understanding of what it means to be healthy. We now know that many problems we experience today are, in fact, understandable in terms of the natural capacities that helped us survive in earlier times. Evolutionary medicine can expose many fallacies behind commonly accepted medical practices and the quackery that fosters popular health fads.

What is Evolutionary Medicine?

Some time ago I was invited to co-teach a course in Evolutionary Medicine at the University of California, Santa Barbara. Professors of parasitology and evolutionary biology, Armand Kuris and Bob Warner, explained that they needed a “real doctor” in the class because their knowledge of human disease and medical treatment was understandably limited. Since inviting a practicing physician to join the mix aligns with the interdisciplinary approach for which UCSB has become known, how could I refuse?

We were fortunate to use the just-published Why We Get Sick as the course text. In it, evolutionary theorist George Williams and psychiatrist Randolph Nesse merged their knowledge of health and disease with emerging archaeology and evolutionary biology to begin answering questions about why rather than simply how we get sick.

It soon became impossible to avoid seeing my own patients as the not-so-distant descendants of our Stone Age forbears. From allergies to the most terrifying cancer, from the ravages of mental illness to the most mysterious autoimmune disease, Darwinian evolution was no longer simply an elegant theory. I was seeing its consequences daily: in the diseases from which my patients suffered but also in how they could be healed.

When I began to share these evolutionary insights with my patients—for example, how we heal from a sprained ankle or why so many people struggle with diabetes— it didn’t take long to see positive effects. These conversations often helped patients develop an entirely new approach to problems from which they’d long suffered as significant improvements in their health soon followed.

The Primal Diet

Consider your teeth. Many of the best-preserved fossils we have found are teeth. That’s because tooth enamel is the hardest, longest lasting substance in the body. These fossils reveal that Stone Age teeth had a rough time of it, undergoing wear and tear as tools for cutting and grinding and chewing many hours a day. Remarkably, however, they had few cavities, the number one dental problem we have today! Since cavemen didn’t have toothbrushes, fluoridated water, dental floss, or dentists, why were their teeth so healthy?

The answer is diet. The bacteria that rot teeth feed mainly on sugars. Unlike proteins and fats, sugars are tiny and sticky. Streptococcus mutans, the main bacterial culprit in tooth decay, lives in the crevices around our teeth and turns sugar into lactic acid that then erodes the surrounding dental enamel, leaving holes—or cavities—in which more bacteria can live. We know from genetic studies that S. mutans has existed in its current form for several million years. It has found a good niche, so why mutate?

When fibrous roots, sour fruits, and occasional honey were the only scarce carbohydrates in a paleolithic person’s diet, these bacteria found very little to feed on. In contrast, our modern diet, overloaded as it is with simple carbs and sugary sodas, offers a bacterial paradise. It’s no surprise, then, that dental cavities are the most widespread chronic disease of childhood in the world today.

This understanding about dental hygiene leads to one of the most frequent and important questions I hear in my practice. What should I eat? Our early human ancestors spent several million years gathering and chasing down every bite of food they ate. The reason we covet sweet, salty, and greasy foods today is that they are important for survival and were rare. Not so today. Simply by reaching into the refrigerator, in a few minutes we can snag all the calories we need to get through the day. We know that eating too much is bad for us, but we seem powerless to stop.

The problem is not just a lack of willpower. We spend billions of dollars a year on foods low in carbohydrates, fats, and sugars or high in vitamins, antioxidants, or omega-3 fatty acids—hoping they will help us lose weight. We dish out billions more on diets, unused gym memberships, surgery, and appetite suppressing injections. Meanwhile, our healthcare system is burdened with hundreds of billions spent on obesity-related illnesses. Gluttony may be a vice, but overeating is an epidemic fed by wholly modern myths about food.

In the past 50 years, we’ve witnessed a tidal wave of obesity as nutritionists, doctors and food manufacturers promoted a fear of fatty foods. But low fat doesn’t mean low in calories. And calories count. Making food with less fat often means packing in more carbohydrates to make it appealing. A low-fat label gives us the false impression that we can eat as much of these “harmless, healthy” foods as we want. But if there were an easy diet that really worked, we’d all know about it. We’d all be thin. The fact that so many diet books sell each year is all the evidence we need that none of them is universally effective.

What did our ancestors eat? We can calculate that to get enough calories our earliest primate ancestors spent up to 12 hours a day finding, chewing, and grinding mostly plant-based foods, much as gorillas do today. As they evolved, their diet expanded to include berries, grubs, fruits, eggs, mushrooms, and the occasional small animal when they could catch one. They were omnivores. We estimate that our ancestors consumed up to 300 different foods in a typical week; today we average about 30.

Many of the roots and vegetables on which ancestral humans thrived were loaded with what your mom might call roughage. Stone Age fruit bore little resemblance to today’s plump, sweet, and juicy produce. An apple then looked and tasted more like today’s hard crabapple. Berries were small, and archaic citrus fruits would make a sour lime taste sweet in comparison. Along with honey and later primitive grains, these fruits were the main source of carbohydrates. Before the advent of agriculture barely 12,000 years ago, most foods contained very few starchy carbs. Before people began cultivating wheat, corn, and rice, the wild versions of these grains grew sparsely, had thick husks, and produced few kernels containing little starch. Root crops were tough and required a lot of chewing. Nuts were tiny and bitter, more like today’s acorns. Fruits were scrawny, fibrous, and none too sweet.

Since fruit and grains appeared for only a few weeks each year, it was vital for our ancestors to eat as much of them as possible when available, before the birds, insects, and other animals could get to them. When fruit ripened, early humans gorged themselves until they were stuffed—then ate again an hour or two later. As a result, our ancestors evolved a nearly insatiable craving for carbohydrates. The only limit was the size of their stomachs, and those could stretch to accommodate the seasonal abundance.

During times of plenty, Stone Age people ate a whole lot more each day than they needed. Those whose bodies were better at storing up those extra calories as fat, bought some insurance for any lean times ahead and passed on their genes for getting fat on to the next generation. This cycle of abundance and want lasted for millions of years. We are its inheritors.

Paleoanthropologists love to debate, “Which came first, bigger brains or more protein in the diet?” We do know that as our ancestors became cleverer, they became better hunters. (Hunting and tracking may indeed be the evolutionary basis for our ability to think scientifically, but that is another, long story.) Eating animals added protein and fat to their diets, providing more calories often for less effort than eating plants. Before farming changed everything, abundant meat was the main course for hundreds of thousands of years.

Taming fire, roughly one million years ago, was a key evolutionary event. Cooking breaks down starch and proteins, making them easier to chew and digest. More energy became available from every bite. Quickly, time spent chewing dropped from 12 to 3 hours a day. This may have been the advent of leisure; time to sit around the fire and tell stories, sing, and pass along knowledge.

Only a few hundred thousand years after harnessing fire, early hominids set out on their first great migrations around the globe. Humans loved meat. In areas where game was abundant, some settled for tens of thousands of years. When meat became scarce, because of a changing climate, overhunting, or just bad luck, it was time to pick up stakes and search for happier hunting grounds. The disappearance of many species of large animals such as massive marsupials in Australia, ground sloths in North America, and bison, elk, and aurochs in Europe, followed the spread of modern humans.

By the late Stone Age, around 50,000 years ago, Homo sapiens emerged as accomplished and resourceful hunters. Studies show they got around half their calories from meat and fat, 40 percent from roots and vegetables, and 10 percent from fruits and berries. These humans, with bodies and brains similar to yours and mine, ate very well. It is from this time that we have evidence of the first obese people. There probably weren’t many of them, but a few were able to lead pampered, sedentary lives, supported by the advancing skills of the growing tribe. Sculpted images of enormously obese women, known as “Venus” figurines, are among the earliest surviving works of art, carved more than 30,000 years ago. Of course, we don’t know the exact meaning these images held for their late Stone Age makers, but it is likely that they were expressions of beauty, or at least attractiveness. Fat women have been cherished for their fertility in most cultures until very recently. “Survival of the fittest” might be better expressed as “reproduction of the fattest.”

Some hormones evolved to shut down our appetites when we had eaten enough fats and proteins. That is why fatty foods are so “satisfying.” However, others, such as GLP-1—the hormone that the new weight loss drugs Wegovy and Ozempic mimic so effectively—are released by sugar and carbs in our diet. They trigger the production of insulin and in our past helped us to pack away those excess carb calories as fat. In higher doses (mimicked by the weight loss injections) they slow down movement of food through the gut, making us feel “full” and thus suppressing our appetite.

Germ Warfare

Drop the word infection into any conversation and watch ears prick up. Mention diarrhea or COVID, and people will begin to edge away. Measles, mumps, or mononucleosis get little reaction any longer. However, up the ante with herpes, tuberculosis, or syphilis, and you can sense people starting to squirm. Invoke pus, bleeding, or plague, and you are edging beyond the bounds of polite conversation.

Most of us have a primal fear of infectious diseases, for good reason. Alongside medicine’s stellar achievements of the past few centuries—hygiene, antibiotics, vaccines, and vastly safer childbirth—many microbes have battled humans to a draw, and some are even gaining ground. As soon as we conquer one infectious disease, another seems to take its place. We defeat smallpox, arm-by-inoculated-arm, and HIV comes out swinging. COVID-19, a more lethal cousin of the common cold, caused us to apply dampers to the world economy for months. We are in an evolutionary arms race with no end in sight. As the human population rises, there are more hosts for our microscopic enemies to attack.

Even with the discovery of antibiotics less than a century ago, bacteria, parasites, and viruses have not retreated. Within a year of the first use of penicillin, some germs were found to resist it. And while vaccines have loosened the stranglehold once held on us by measles, mumps, hepatitis, and polio, as yet we have no shots to prevent HIV, herpes, West Nile, or a horde of other viruses. In the tropics, new strains of influenza emerge annually from animal hosts and spread at jet speed onto the wider world stage.

On the home front, patients come to me every day sneezing and coughing, aching and fevered, hoping an antibiotic will provide a quick fix. Sadly, these drugs have no effect against viral infections and, when used inappropriately, breed drug-resistant bacteria in our bodies. At the same time, some people worry that vaccines against the killer diseases of childhood actually damage their children. They resist immunizations, depending on others to get the shots that derail an epidemic.

Fighting infections has never been easy. Microbes invade our bodies and evade our immune systems in clever ways that science is still deciphering. In the past, they jumped from person to person, while today they leapfrog from city to city. They are nimble adversaries. Evolution happens when genes mutate and spread to the next generation—and many bacteria produce a new generation every 90 minutes!

Nevertheless, working in our favor are the very Stone Age defenses we often misunderstand. Our healthy skin, thick mucus, fever, inflammation, and antibodies are the body’s first responders on the front lines of the fight against infections. We suppress them at our peril. Understanding how our cave-dwelling forebears survived such onslaughts, long before they could reach for a bottle of pills, can teach us how to respond better to infections today.

A Few Paleolithic Symptoms That Have Lingered On

Coughing evolved to clear our airway of foreign particles—dust blown by the wind, smoke from a fire, and food inhaled when we meant to swallow. By forcefully expelling air from our lungs, coughing gets the grime out. A sneeze serves a slightly higher purpose.

Mucus, or phlegm, is also a defense mechanism. This complex and wonderful concoction of proteins and other gooey stuff entraps and disarms germs, helping us to swallow them into our stomachs where powerful acids wait to destroy them.

What happens when we are confronted with a cold virus? A virus is really very simple. It’s just a bundle of genes, wrapped in a protein coat. All it needs is to find a good place, i.e., you, in which to set up housekeeping, make a few million copies of itself, and then move on. For contagious diseases, it’s the moving on that matters. If they can’t get out of us to a new victim, they die out. Cold viruses such as COVID are spread on airborne droplets of moisture when we cough. Making us cough, by irritating our airways, is the evolutionary tactic a virus uses to spread itself. Diarrhea is a similar strategy of gut viruses, the “stomach bug.”

Well-meaning parents often encourage their sick children to “cough it up” to clear phlegm out of their airways. However, coughing actually irritates our airways. It’s like scratching an itch. The more you scratch, the more irritated it gets. Coughing actually makes a sore throat worse and spreads the virus to others. We are playing right into the virus’s hands.

Sneezing is even worse. Have you ever seen the famous photo of a sneeze, spraying droplets ten feet across a room? Sneezing serves the virus’s purpose by loading them on an express flight to the next victim—our children, coworkers, spouses, or strangers. This is why masks are useful in stopping the spread of airborne viruses. To really be helpful, however, you need a really good mask, such as an N95, made of multiple layers of hydrophobic filters that stop the droplets from ever reaching your nose.

When you feel the need to cough, don’t let the virus win. Suppress it. By drinking a small amount of liquid, you can help your body eliminate the germs by ingesting them. At the same time, you will prevent the irritation and swelling that coughing brings. Sometimes you can’t help but cough. In those cases, your mom had it right: Cover your mouth. Not just a polite hand in front of the face— really press your hand or inner elbow over your mouth to seal off any air from coming out. (And then be sure to wash your hand—thoroughly). This decreases the rapid flow that irritates your airway as well as stops the spread of germs. This was common advice 50 years ago when coughing around others was considered impolite at best.

Unfortunately, all the over-the-counter cough remedies containing dextromethorphan (the DM in Robitussin-DM) and other ingredients don’t do much. They coat your throat, but they don’t help suppress coughing. Without any evidence they are effective, we spend billions a year on cold remedies such as Echinacea, Airborne, vitamin C, Dayquil, Nyquil, antihistamines, decongestants, cough suppressants, and fever reducers that do nothing to shorten the infection and have minimal effect on the symptoms. Some even work against the healing process.

When we take an antihistamine to dry up the sniffles, it limits the mucus available to help engulf the virus. The sole over-the-counter expectorant used in the United States, guaifenesin, thins mucus, which makes it less effective at trapping bacteria. Codeine-based cough suppressants, now very hard to come by, can help and are useful when simply making an effort to suppress the cough fails, especially at night when we need to sleep.

The most effective way to defeat a cold virus is to recognize that we are all in this together. Once we’re infected, washing our hands and covering up when sneezing or coughing is the kindest thing we can do for others. Rest, stay hydrated, and let your immune system do what it evolved to do. When a true cure for the common cold comes along, it won’t need to be advertised or sold in alluring packages at the checkout counter. It will be obvious to all of us because of how well it works, every time. And then, like polio and smallpox, colds will be history.

You Give Me Fever

If evolution is a long war between us and germs, then a cold is a daily skirmish on the front line. While viruses reproduce quickly, our bodies react more slowly. It can take days for our immune system to mobilize specific antibodies to fight a virus.

Over millennia, we evolved a quicker response. Germs are adapted to infect us when our body temperature is normal. By turning up our internal thermostat when we first detect an infection, our bodies make it harder for the virus to grow. Shivering probably evolved to warm us when we got cold. A shaking “chill” making us hot—called a rigor in medicine—is often our first line of defense. When we feel a chill, we want to take to our beds because that is exactly what we should do. If we take a fever reducer, such as aspirin or Tylenol, we can suppress the fever and may feel well enough to be up and around. This can divert energy our body needs to fight off the infection—and affords the virus many more opportunities to spread to others.

Increasing our temperature also speeds up the activity and circulation of disease-fighting white blood cells. In early mammals, those who responded to microbe invasion by developing a fever and limiting their activity would have survived better and passed on these defenses to their descendants. It makes evolutionary sense that children get hotter faster than adults. Kids are more likely to run into germs they have never encountered before and to which they have no immunity. They need the quick general defense a fever can muster.

If a fever provides an evolutionary advantage for a near naked primate, what happens when we bundle up in blankets? We can cause our temperature to rise higher than it naturally would and so overshoot the safety mark. Exceeding 103F (39.5C) degrees can do more harm than good. Extreme temperatures can lead to seizures in children and dehydration and worse in adults. Taking a fever reducer such as aspirin, acetaminophen (Tylenol), ibuprofen (Advil and Motrin), or naproxen (Aleve) is entirely appropriate in these conditions. These medications all short-circuit our body’s natural ability to raise a fever.

Is there any sense in the old saying, “feed a cold and starve a fever”? When we have a simple cold, eating has been shown to quadruple the production of the virus-fighting hormone interferon. When we start to get hot, however, it’s not food we need but fluids. It’s no coincidence that a fever kills our appetite. Fluids trigger the production of interleukin-4, which works particularly well against many of the bacteria that cause fevers. The return of hunger is usually a sign that you are getting better.

A Paradox of Prevention

Polio offers a good example of how “progress” can inadvertently help a virus to spread in a way that evolution couldn’t. Polio is a virus that usually grows in our guts. When excreted, it survives for weeks in freshwater pools and stagnant ponds.

Throughout history, infants who were exposed to the virus early in life while they were still protected by antibodies in their mothers’ milk, usually experienced only a mild infection. Fewer than one in a thousand had the paralytic form associated with the epidemics of the last century.

Paradoxically, modern hygiene in the late nineteenth century prevented infants from ingesting water contaminated with the virus while still breastfeeding. Coming in contact with that virus later in life in swimming pools or ponds, at a time when they were no longer protected by maternal antibodies, caused them to contract the much more serious paralytic form of the disease. By 1900, small epidemics of paralytic polio began to appear throughout the industrialized world. By 1952, with breastfeeding at a minimum and better sanitation more widely practiced, polio infected thousands of children who had failed to acquire immunity in infancy. At its peak in 1950, the epidemic paralyzed 60,000 people a year.

A vaccine developed in 1952 by Jonas Salk arrested the spread of the disease within a few years. Polio is now almost wiped out. However, certain religious and political objections still hamper universal use of the vaccine.

Other diseases that could be eradicated, linger on—mumps, measles, chickenpox, and hepatitis. As vaccination has made certain childhood infections so uncommon in Western countries, some people have become comfortable with not vaccinating their children. These parents are counting on the immunity of those who do get vaccinated (herd immunity) to prevent the spread of these childhood illnesses to their own kids.

Remember measles? Measles ranks high on the list of all-time lethal diseases. By some estimates, measles wiped out up to a third of all the people along the trade routes of the Middle Ages—and that was even before the European Age of Exploration opened vast new territories for the virus. In the past 150 years it has killed 200 million people—including 128,000 in 2021, most under the age of five.

The measles virus evolves very slowly. With so many innocent immune systems to infect in the past, it didn’t need to change much to find plenty of hosts. Luckily, it’s easier to make vaccines for slower-changing viruses because they are so stable. Faster-changing viruses, such as COVID, HIV, and influenza, form more elusive moving targets.

Today, many of us have forgotten how dangerous many formerly common infections were. Measles was a worldwide scourge. Mumps can make men sterile. Rubella can cause birth defects when it infects a pregnant woman. One vaccine, MMR, prevents all three. Diphtheria and Whooping Cough (Pertussis) were once dread diseases of childhood. Tetanus kills. Here too a single vaccine, DPT, prevents all three. Smallpox, which killed 300 million people in the last century, has now been eradicated by a worldwide vaccine campaign.

By skipping vaccination, some parents hope their children will dodge a risk. However, serious side effects of the vaccine occur at a much lower frequency than serious complications of the disease. Fears once raised that measles vaccine causes autism have been thoroughly debunked.

If enough people avoid vaccination, those once serious diseases will continue to evolve and come roaring back. Mumps and whooping cough are returning to the United States. Polio is still making its crippling rounds. Skipping vaccination is a terrible gamble. When these viruses strike, unvaccinated children are the first to fall.

During the COVID-19 pandemic, the science of vaccination became even more politicized. This is unfortunate because priming our immune systems to recognize and fight off infections is one of the most effective and least harmful methods of protection we have. In the Stone Age, every infection set off a race between the “bugs” and our defenses. Vaccines activate this age-old system by injecting tiny amounts of weakened strains of these germs, allowing us to be forearmed.

The Not So Common Cold

Colds are caused by viruses—not by being out in cold weather or getting tired or soaked with rain. Understanding the evolutionary origins of viruses can help us stop them in their tracks. Most cold viruses evolved in enormous prehistoric populations of migrating birds and beasts. Because there were millions of animals in these flocks and herds, viruses could spread from one individual to another, never needing to infect the same creature twice—much like a wave spreading across the water.

By contrast, our paleolithic ancestors lived in isolated bands of a few dozen people. Archaeologists estimate that as recently as 70,000 years ago there were only 10,000 humans alive on the entire planet. Each family or clan clung together as closely as possible, seldom interacting with other groups. Stealing food or mates posed too great a risk to encourage much contact. So even if an animal virus managed to infect a person, it was very difficult for it to spread beyond the group it first entered. The common cold was not so common back in the Stone Age. Clearly, we aren’t going to solve the problem of colds by going back to living in isolated tribes. However, the insights of evolutionary medicine can help in arresting the rapid spread of these and other viruses in our modern world.

Under the Influenza

Influenza, the “flu,” kills around 400,000 people worldwide, and 36,000 people in North America—most years. In flu pandemics, which occur every 20 years or so, tens of millions die.

As with the common cold viruses, the earliest humans didn’t have enough contact with other groups to allow the flu to spread. Yoshiyuki Suzuki (Oxford University), who studies the evolution of influenza, estimates the first flu epidemics in humans occurred no earlier than 8,000 years ago. This coincided with the development of farming and village life, when people, fowl, and pigs first began living cheek by beak by jowl.

Unlike the more stable measles, mumps, and chickenpox viruses, the flu virus changes its outward appearance (that is, it evolves) rapidly. Shrouded in an ever-varying coat of proteins, like a shape-shifter in a science fiction novel, it cloaks itself in order to hide from our immune systems. However, once it gets past our defenses, it always causes the same miserable symptoms—high fever for days, severe body aches, a racking cough, and nasal congestion. It’s like a cold, only much worse.

Flu’s ability to change its surface coat so rapidly forces us to come up with a revised flu vaccine every year. Modern medicine maintains a constant watch for emerging strains in order to predict which to include in the following year’s vaccine. Before the advent of annual flu vaccines, many more people got sick and died of the flu every year, especially those over 60.

Occasionally, farmers and food handlers are infected with a strain of flu derived from another animal at the same time they have a human flu virus in them. When this happens, the two kinds of flu can merge to become an entirely new strain. The combined virus is often better at infecting us because we have no antibodies that recognize its novel appearance. This is how the avian flu pandemics of 1918, 1957, 1968 and the swine flu pandemic of 2009 occurred, and also why some people think COVID-19 originated in a live animal food market in China. (Doing justice to the debate between the “wet market” and the alternative “lab leak” theory of the origin of COVID-19 requires a separate article).

Quarantine, an early scientific method for halting the spread of disease, yields excellent results—if it is done quickly enough. That’s how SARS, the first well-known Coronavirus, was stopped in 2003. With proper public health policies in place, and enough people who take them seriously, we could likely contain any newly emerging virus within weeks, even a novel strain of the flu, without relying on vaccines. However, quarantine is expensive, inconvenient, and may even deprive people of some rights or even their livelihood for a short period. Still, that price would be minuscule compared to the devastation of a full-blown pandemic such as we have recently experienced.

On the home front, the best way to protect ourselves is to be clear about how such germs spread. Not being “part of the herd” and not going out in public when we are sick can go a long way toward stopping the spread. Covering our mouths when we cough or wearing effective masks helps a lot, as does thoroughly washing with plain old soap and water. Washing is a lot more effective than hand sanitizer, which doesn’t kill all types of viruses or even fully remove them from our hands.

Toxins and Cancer

Many things in our world are toxic. Radium, benzene, arsenic, and asbestos are widely known to cause cancer, but most of us are rarely exposed to them. On the other hand, smoking, drinking, obesity, and excess sun exposure together account for about 50 percent of all cancers.

The most significant food toxin known to cause cancer in humans is Aflatoxin, a fungal byproduct found in moldy peanuts. It contributes to the occurrence of liver cancer, mostly in parts of Africa and Asia where the hepatitis B virus, a cofactor for this cancer, is prevalent and moldy food is common. Yet, if you search online, you will find a long list of alleged cancer-causing culprits, including soda, hydrogenated oils, microwave popcorn, farmed fish, refined sugar, white flour, pickled, salted or smoked foods, and grilled red meat. We frequently hear that some common chemical such as the sweetener we use in our coffee “causes cancer.” None of these claims is backed by scientific evidence.

When scientists say a chemical “may cause cancer,” it usually means it was tested and found to damage the DNA of a bacteria or cause tumors in rats. However, such research uses doses hundreds or thousands of times what a person would ingest, pound-for-pound. And rats are genetically different from you and me. They get cancer very easily and that’s why we use them for tests. Just showing that a toxin causes cancer in rats, or abnormal changes in bacteria or cells in a Petri dish, doesn’t come close to demonstrating it will do so in humans. Our livers are three times the size of the whole rat and work hard to protect us. Please don’t misunderstand what I’m saying. I am a scientist. I trust good evidence. However, not all research is done well and we must remain skeptical—though not cynical—especially of fear-inducing claims.

Since we can’t ethically test toxins on humans, we look for “natural experiments”—groups of people exposed to a chemical at work or by accident. We then compare them against a similar but unexposed group to see what effects these toxins have. Beyond a few well-studied carcinogens—and Erin Brockovich’s cinematic arguments about a cancer cluster—there is scant linkage between trace toxins in our environment or food and cancer or other illnesses.

Your plastic water bottle, for example, won’t give you cancer. If it did, we would have detected thousands, indeed millions, of cancer cases already. The same is true for tap water. There’s no credible evidence that food preservatives, deodorant, stress, aluminum, processed foods, aspartame (Equal), or saccharin (Sweet’N Low) cause cancer. If you examine the reports carefully you will see that they are usually based on extrapolating from experiments on cells or animals given huge relative doses and always contain qualifiers such as “can” or “may” cause cancer.

We have always lived in a world chock full of poisons, and we have evolved potent defenses against the natural threats we’ve encountered in our long ascent from the primordial swamp. Our not so fragile forebears thrived among greater toxic threats than we might imagine. Why do some things smell and taste “bad”? Often it’s because they were bad for us. Our tough skin, hardy livers, and purifying kidneys evolved to neutralize many toxins that passed the nose test to make their way past this first line of defense.

Meanwhile, there is no shortage of products being offered to help our bodies “cleanse” ourselves of toxins by using homeopathy, chelation, or colonics. We can buy “probiotics” to counter the antibiotic we took when we had a cold. (The marketers don’t mention that all yogurts have these bacteria—it’s what makes them yogurt in the first place.) We can sweat in saunas, chill in ice baths, soak in spas, or spend money on supplements—all in the name of “cleansing.”

Is there any real evidence that people who make such efforts are healthier than the rest of us? Not one bit. Contrary to countless celebrity testimonials, decades of research provide zero evidence that using any detoxifying products actually improves health or prevents cancer.

Dodging Cancer

There’s a good evolutionary reason why we heal so well from wounds and infections but have trouble fending off cancer. Natural selection, the weeding out of harmful traits, has a hard time acting on illnesses that occur later in life. By the time most cancers appear, people have usually finished having children. A cancer predisposition that appears only after our reproductive years gets a free pass to the next generation.

Children do get cancers, of course. Terrible as these cases are, fortunately they are rare compared to other causes of death. Most cancers occur in older people. The single most important reason cancer is increasing in the developed world is because we are living longer, not because of toxins in our food and environment.

Cancer still kills one in six people worldwide, but that means 84 percent of us will die of something else. In less-developed countries where life expectancy is shorter, most people die of infections and accidents, as in times past. In those places, cancers don’t even make it into the top ten causes of death.

While research has made significant progress against certain cancers, our fear leaves plenty of openings for a Pandora’s box of alternative therapies. This has always been the case with poorly understood diseases. In the days before the discovery of the poliovirus, rumor attributed polio to everything from fleabites to airborne toxins, insecticides, and poverty. When the vaccine came along, some people thought it was the cause. Many of these same suspects are blamed for cancer today.

One popular theory suggests that a diet low in fiber causes colon cancer. This idea arose from a 1979 book that reported a lower rate of colon cancer in men in Africa than in the West. The author attributed this to their high-fiber diet and using a squatting posture during defecation. He forgot to take into account that men in Africa die younger than men in the West, and the rate of colon cancer increases as we age. A meta-analysis of more than 80,000 participants demonstrated that fiber doesn’t prevent colon cancer. Still the myth lives on in health food stores and breakfast cereal ads.

Antioxidants are now popularly claimed to prevent cancer (as well as aging, heart disease, and “inflammation”). These molecules do limit oxidation, a kind of cell damage that can contribute to cancer—in the lab. Remember, however, oxidants and free radicals are part of how our cells fight off infection and clear damaged cells from our bodies! When tested in people, there is no evidence that antioxidants—including beta carotene, lycopene, acai berries, cumin, turmeric, or vitamins A, C or E—can prevent cancer. Vitamin A in excess can cause liver damage, osteoporosis, hair loss, dry skin, and birth defects. It seems our bodies make all the antioxidants we need, so supplementing them can make matters worse. Studies done in actual people, not Petri dishes, show that excess vitamin E, folic acid, and beta-carotene can actually increase the risk of cancer.

Vitamin Supplements

Our Stone (and Iron, Bronze, Middle, and Steam) Age ancestors survived without ever taking vitamin pills, but it wasn’t always easy. In hard times, especially when they roamed into new territory, experienced harsh winters, droughts, and floods, food could be hard to find. Their bodies evolved to be very good at absorbing whatever vitamins they needed, especially when they were in short supply. We inherited this ability to store most vitamins for times of scarcity.

Today, of course, we can buy a plethora of vitamins and minerals off the shelf, mixed in myriad combinations. Some of us gulp down enough to choke a horse. This is a high-risk endeavor because an excess of certain vitamins (A, D, E, and K) can be toxic. Some of our legislators are enthusiastic supporters (read: on the payroll) of the vitamin industry. Vitamins are sold as “dietary supplements,” not as drugs, and are largely unregulated. There are no safety inspections or uniform requirements for those who manufacture or market them, and therefore no guarantee you are getting what you pay for.

This article appeared in Skeptic magazine 28.4
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The only real proof we need for the benefit of vitamin pills should be that taking them makes us healthier. However, people who take them, in small or mega doses, are sick just as often and have just as many other illnesses as those who don’t. Of the 13 known vitamins, six can be taken in overdose. Every year more than 60,000 people in the United States overdose on vitamins—80 percent of them are children under the age of six.

If you eat a variety of unprocessed food you get all the vitamins, minerals, and antioxidants you need. Let your body do all it evolved to do, and you will get just the amounts you need.

Alternative Medicine

Many “alternative” therapies, such as acupuncture, massage, Reiki, homeopathy, aromatherapy, naturopathy, and ayurveda promise to make us well while causing less harm than medicine. Do they work?

As most doctors and some alternative practitioners know, most people who seek medical attention get better on their own, no matter what we do to them. This is because most illnesses are mild and self-limiting. Still, many of us are not content with letting nature take its course. When we feel a sniffle, we reach for some over the counter medicine. None can make us better. When we get better, we want to believe it was because of what we took.

We spend billions each year on brand named pills and folk remedies that have lingered from earlier times. They became popular in the same manner as do all superstitions. One person tried them, got better, and believes the treatment worked. They pass this along through retelling and retailing, and so a so-called cure is born.

Alternative medicine practitioners now use TikTok, YouTube, Facebook and X (Twitter) to speed the spread of their “cures.” Although some of these practices are actually harmful, the false hope they offer to the seriously ill is misleading at best and criminal at worst. Sadly, modern medicine has sometimes been little better, pushing marginally useful pills or physical therapy on us when time and a better understanding of the natural process of healing would accomplish just as much—and at less risk and a lower cost.

What’s Next?

If you find this approach intriguing, I urge you to look further into what evolution has to say about how we heal from injuries, why allergies are more common today than in earlier times, how much sleep we really need, who we find sexually attractive, the benefits of grandparents, how many periods should a woman have in her lifetime, why morning sickness was good for us, why we get depressed, the advantages of Attention Deficit Disorder, what use are emotions, the origins of anxiety, whether cholesterol is really bad for us, why do so many people need glasses, how does sickle cell disease protect some people from malaria, and what can we do to live longer healthier lives. These topics and dozens more are the subject of the fascinating new science of Evolutionary Medicine.