Chronic illness, constant inexplicable headaches, a vague pain where there ought not be one—too many people come to live with one or more of these irritations, some of which prove to be more than mere irritations. In this excerpt from our new book, The Hunter-Gatherer’s Guide To the 21st Century, we aim to provide some tools that will help you understand and improve your own health.

Against Reductionism

Monarch butterflies raised in captivity don’t know how to migrate. Attempt to keep indri—large lemurs that eat dozens of species of leaves on a regular basis—in captivity, and you’ll find that you can’t replicate their diets sufficiently to keep them alive. Observe a problem (of your own creation) of rats in Hawaii eating your sugarcane crop, attempt to solve it by bringing in mongooses to eat the rats, and find yourself soon thereafter in a landscape bereft of native birds, reptiles, and mammals, but still plenty of rats.

None of these should surprise us—complex systems are just that: complex. Reducing them to a few easily observable, easily measurable parts can feel like success, but reductionism generally comes back to bite those who practice it. Add to this the hyper-novel condition of being able to isolate and synthesize molecules that cause physiological change, and we have a recipe for medicalizing the world, which often makes us less healthy, not more so. And yet, the modern approach to medicine can broadly be characterized as reductionist.

It’s a mistake to imagine that we are simply machines, with fixed rules and codes, rather than people. This is the engineer’s approach to what humans are (as opposed to the biologist’s), and it vastly underappreciates how complex and variable we are. 

Considering the Risks of Reductionism as We Choose What to Put in Our Bodies

From fluoridated drinking water to shelf-stable foods with unintended consequences, from the myriad issues with sun exposure, to whether GMOs are safe—we are constantly seduced by reductionist thinking, led astray by the fantasy of simplicity where the truth is complex. Reductionism, particularly with respect to our bodies and minds, is harming us. Sometimes it is even killing us.

Early in the 20th century, fluoride was discovered to be correlated with fewer cavities. So fluoride was put in many municipal water supplies to decrease tooth decay. The fluoride in drinking water is a by-product of industrial processes, though, not a molecular form that appears in nature or has ever been part of our diet. That’s one point against it. Furthermore, we find neurotoxicity in children who are exposed to fluoridated drinking water; a correlation between hypothyroidism and fluoridated water; and, in salmon, a loss of the ability to navigate back to their home stream after swimming in fluoridated water. Is fluoride a magic bullet for reducing cavities, with no costs to other aspects of health? Seems not. More to the point, the quest for magic bullets, for simple answers that are universally applicable to all humans in all conditions, is misguided. If it were that easy, selection would almost certainly have found a way. Think you’ve found a solution that is too good to be true? Look hard for the hidden costs. 

The modern food supply chain benefits from shelf stability of processed foods—while the foods along the perimeter of a grocery store tend to be less processed, and therefore less shelf stable, nearly all of the foods in the middle of grocery stores have expiration dates many weeks or even months away. Minimizing fungal growth in our food is certainly desirable, but at what cost? Propionic acid (PPA) inhibits mold growth, and is a prominent additive to processed foods for that reason, but its presence in utero affects fetal brain cells and is linked to an increase in diagnoses of autism spectrum disorder of children thus affected. We should not be surprised that being “shelf stable” comes with costs.

Similarly, people who live near the poles, or who rarely go outside, can come to suffer from short stature, and weak and curved bones—a condition known as rickets. Vitamin D was identified as the missing molecule for such people, and as we seem to like our pills, we are provided vitamin D as a stand-alone product, or as an additive to milk. But what does our history have to say on the subject?

At the end of the first millennium, the Vikings, unlike other northern Europeans, did not succumb to rickets. This turned out to be due to a diet rich in cod. They didn’t know that it was the cod that was keeping them healthy and strong, but it was. And we can say with absolute certainty that they did not achieve health through the consumption of a distillate version of vitamin D packaged in pills or tinctures. The historical evidence suggests that most of us could go out in the sun for a bit every day, or eat cod, or do some combination of both, but pills are easier, and they reek of scientism, which is easily mistaken for science and for “taking control of your health.” How often have you heard someone say—maybe even said yourself—something like, “I’m being proactive; I’m supplementing with vitamin D!” (Or C, or fish oil, or whatever the quick-fix product du jour is.)

Once again, we should not be surprised to find that this reductionist and ahistorical approach has yielded no evidence to support the claim that adding vitamin D to your diet will keep your bones strong; indeed, lack of vitamin D may be a symptom, rather than a cause, of rickets and related conditions. Not only is loading up on vitamin D not the solution, we are not even sure its scarcity is the problem.

Related to the reductionist thinking around vitamin D is the fact that for decades now, we have received a nearly universal recommendation to slather ourselves with sunscreen whenever we’re in the sun. Reduce your exposure to the sun, the logic goes, and skin cancer rates fall. True enough. Guess what goes up when sun exposure goes down, though: blood pressure. And as blood pressure climbs, so do rates of heart disease and stroke. People who avoid the sun have higher overall mortality rates than do people who seek it. A research study on Swedish women reported this remarkable result: “Nonsmokers who avoided sun exposure had a life expectancy similar to smokers in the highest sun exposure group, indicating that avoidance of sun exposure is a risk factor for death of a similar magnitude as smoking.” So reductionist scientism has misled us yet again, and likely caused many deaths. Should we stay out of the sun and take vitamin D, or seek moderate sun exposure and get the nutrients we need by seeking something closer to an ancestral diet? An evolutionary analysis suggests the latter. At least on this topic, the medical literature is catching up to that conclusion as well.

Given this track record of reductionist science and health advice, should we trust that GMOs are safe, just because those who would profit from their acceptance, either intellectually or financially, tell us they are? We suggest not. Are some GMOs safe? Almost certainly. Are all GMOs safe? Almost certainly not. How will we know which are which, and can we rely on those who have created them to be vigilant on our behalf? Until we know the answer to those last questions, we suggest steering clear.

Finally, it is worth noting that some of the major successes of Western medicine—surgery, antibiotics, and vaccines—are firmly rooted in a reductionist tradition and have saved millions of lives. The problem we are highlighting is the overapplication of a reductionist approach. The germ theory of disease—in its simplest formulation, the recognition that pathogens cause much disease—led to the discovery and formulation of antibiotics, a huge health boon for humanity. Then we overgeneralized, and imagined that all microbes are bad for us.

We are now coming to realize that our microbiome has evolved with us and is necessary for a healthy gastrointestinal tract. Antibiotics are one of relatively few powerhouse tools of Western medicine, but as they have been overprescribed, we have seen an attendant rise in people becoming sick, often chronically so. Just as people are falling ill from lacking healthy microbiomes due to overprescription of antibiotics, so too are our livestock. Furthermore, there are unintended side effects of many antibiotics that will be shocking to most people. Heather’s personal experience with the unintended consequences of antibiotics was a ruptured Achilles tendon. It is now understood that tendon and ligament injury is one side effect of Cipro (and all of the antibiotics in that class, the fluoroquinolones), which Heather took in quantity in the 1990s to ward off GI bugs while conducting research in the tropics.

From fluoridated drinking water to antifungals in shelf-stable food, from sunscreen to the overuse of antibiotics—over and over we make the same kinds of mistakes. Combine reductionism with a tendency to overgeneralize, in a hyper-novel world where quick but expensive and potentially dangerous fixes are common, and we have explained some of the major errors of modern health and medicine.

Rather than the reductionism that pervades much of modern medicine, we need flexible, logic-based, evolutionary thinking with which to navigate. In February 2020, early in the COVID-19 pandemic, both the World Health Organization (WHO) and the US surgeon general repeatedly told the public that “masks aren’t helpful” in protecting against SARS- CoV-2. In this case, too many people listened to the authorities rather than thinking through the logic themselves. Why, for instance, if masks are pointless, are they exactly the equipment used by health professionals when trying to avoid infection from respiratory ailments? When the directives were later reversed, people who had followed them based on authority alone lost faith in those same authorities. It was then difficult to regain the public’s trust sufficiently to encourage a careful, nuanced approach to reducing the spread and impact of this novel coronavirus. Simple prescriptions make snappier sound bites, and they are easier to remember for those looking for set-and-forget solutions, but when they fail you, you are left with nowhere to stand, no ability to problem solve for yourself. Rather than blindly “trusting the science” or following the lead of authorities, learn to do at least some of the logic for yourself, and seek authorities who are willing to both show you how they arrived at their conclusions and admit when they have made mistakes. We hope this can help you become a better problem solver.

 *References to the scientific literature were removed for the purposes of streamlining this excerpt.

Excerpted from A HUNTER-GATHERER’S GUIDE TO THE 21ST CENTURY: Evolution and the Challenges of Modern Life by Heather Heying and Bret Weinstein (Portfolio; September 14, 2021).