What Doesn't Kill Us: How Freezing Water, Extreme Altitude, and Environmental Conditioning Will Renew Our Lost Evolutionary Strength

by Scott Carney

Nature gave us the ability to heal ourselves. Conscious breathing and environmental conditioning are two tools that everyone can use to control their immune system, better their moods, and increase their energy.

The Western-lifestyle makes it all-too-easy to take nature for granted. All mammals share the same underlying physiology, but somehow humans are so caught up thinking big thoughts with their big minds that they’ve come to believe that they’re different from everything else around them. Sure we can build skyscrapers, fly airplanes and simply turn up the thermostat to combat the cold, but it turns out that the technologies that we believe are our greatest strengths are also our most tenacious crutches. The things we have made to keep us comfortable are making us weak.

Conscious breathing and mental focus can jump-start a chemical change to alkalize the body, while immersion in cold water creates a mental and physical mirror for seeing ourselves in a state of fight-or-flight. Feeling that change is powerful.

Reasonable people take 5 to 10 days to reach the top of Kilimanjaro, climbing in slow and deliberate stages along the route so that their bodies can generate enough new red blood cells to compensate for the decrease in oxygen as the altitude increases. But we are not reasonable people. Our rather audacious plan is to make the summit in 2 days.

In the past six million years of human evolution our ancestors mounted expeditions across frozen mountains and parched deserts with only a whisper of technology to aid them. While they might not have aimed to get up this particular mountain, they surely crossed the Alps and the Himalayas, navigated oceans, and populated the New World. What power did they have that we have lost? More important, is it possible to get it back? The underlying hypothesis of this expedition is that when humans outsource comfort and endurance they inadvertently make their bodies weaker, and that simply reintroducing some common environmental stresses to their daily routines can bring back some of that evolutionary vigor.

With no challenge to overcome, frontier to press, or threat to flee from, the humans of this millennium are overstuffed, overheated, and understimulated.

Effortless comfort has made us fat, lazy, and increasingly in ill health.

a plunge into ice-cold water not only triggers a number of processes to warm the body, but also tweaks insulin production, tightens the circulatory system, and heightens mental awareness.

By incorporating environmental training into your daily routine, you will achieve big results in very little time.

Yet no environmental extreme induces as many changes in human physiology as the cold does.

Weak circulatory muscles are a side effect of living in a very narrow band of temperature variation. The vast majority of humanity today—the entire population that spends the bulk of its time indoors and/or whose only experience when it gets too cold or too hot is wearing state-of-the-art outdoor gear—never exercises this critical system of their body. Even people who appear physically fit, with lean muscles and chiseled abs, might be secretly hiding weak circulatory muscles. And the stakes are huge: In the long run, circulatory diseases contribute to almost 30 percent of the world’s mortality.

The body that you have isn’t too different from an ant colony. Long before animals ever appeared on earth, in a time when life comprised mostly single-celled organisms, microscopic bean-shaped bacteria called mitochondria flourished in the wild. These single-cell life-forms ate up oxygen from the environment and expelled an energy-rich waste product called adenosine triphosphate, or ATP. Over the course of millions of years, larger single-cell critters needed more energy to perform complex functions. Rather than develop a novel approach to creating ATP, they evolved to absorb mitochondria into their own cellular structures. Thus the first animal cells were born out of a symbiotic relationship. If you were to peer through a microscope into almost any cell in the body, you would find thousands of mitochondria sucking up oxygen and excreting ATP.

In addition to mitochondria, scientists estimate you have more than 10 trillion other microbes in your body, comprising more than 10,000 different species, and accounting for 1 to 3 percent of your body weight.

Without stimulation, the responses that were designed to fight environmental challenges don’t always lie dormant.

This book is largely about what happens when we reexamine our relationship with the environment and see ourselves as a part of something bigger than the comfortable spaces we mostly choose to live in. It explores how changing the environment around the body also fundamentally changes the body itself. More importantly, it shows how it is possible to manipulate our external environment to trigger autonomic responses in predictable ways. Once you realize that you can manipulate deep parts of your physiology by intentionally tweaking identifiable preprogrammed responses, you can begin to cede aspects of that automation to your consciousness.

Hof promises he can teach people to hold their breath for 5 minutes and stay warm without clothes in freezing snow. With a few days of training, he says, I should be able to consciously control my immune system to ramp it up against sicknesses or, if necessary, possibly even use it to suppress autoimmune malfunctions such as rheumatoid arthritis and lupus.

We cycle between hyperventilating and holding our breath for almost an hour, and every repetition makes it incrementally easier to hold on just a little bit longer. Hof tells us that the quick breathing adds oxygen to our blood supply so that, at least until we use it up, we won’t have to rely on the air in our lungs to survive. The autonomic urge to gasp for air is based on the mind’s ordinary programming: oxygen-depleted lungs means it’s time to breathe. My nervous system has not yet realized there is still oxygen in my bloodstream.1 The heavy breathing lets me trick my nervous system into doing things that it isn’t evolutionarily designed for. In other words, I am hacking my body.

The breathing technique emerged naturally. He started by mimicking the rapid breaths people take instinctively when they plunge into icy water, which he says are similar to the breaths a woman takes during childbirth. In both cases the body switches to an instinctual program. When Hof dunked under the ice, his body went naturally from rapid breathing to a breath hold. That’s when he began to feel changes in his body.

The way Hof explains it, humans must have evolved with an innate ability to resist the elements. Our remote ancestors marched across endless expanses of frosty mountains and navigated parched deserts long before they invented the most basic footwear or animal-skin coats. While technology has made us more comfortable, the underlying biology is still there, and Hof believes the key to unlocking our lost potential lies in re-creating the sorts of harsh experiences our ancestors would have faced.

The body’s natural reaction to cold is self-preservation. To keep the core warm, the muscles that control the arteries clench tightly and restrict the flow of blood only to vital areas. The process is known as vasoconstriction. This is why frostbite starts in the extremities: the lack of blood flow to those areas makes them cool much faster than if they were flush with warm blood. The sudden change to heat has the opposite effect. Arteries suddenly pop open and blood surges back into those cold areas, generating an excruciating wave of pain.

After years of exposing himself to the cold, Hof says that he can now operate his arteries much like he could his fingers. That is, he can consciously restrict the blood flow of his limbs and send it to any part of his body that he wants to.

What we know about how the human body reacts to cold comes mostly from gruesomely accurate studies that emerged from the Dachau death camp. Nazis tracked Jewish prisoners’ core temperatures as they died in ice water. As terrible as they are, these morally compromised studies have helped doctors understand how quickly the body loses heat in such conditions. Sitting in 32-degree water, humans begin to feel sluggish after only a minute or two. By 15 minutes most people fall unconscious. They die between 15 and 45 minutes depending on their underlying physiology. When the core body temperature falls below 82 degrees, death is almost inevitable. Measured against that data set, Hof seems to perform miracles.

In 2007, at the Feinstein Institute for Medical Research on Long Island, Kenneth Kamler, a world-renowned expedition doctor who has worked on Everest, observed an experiment in which Hof was connected to heart and blood monitors and immersed in ice. At first the experiment hit a major snag. The standard hospital devices that track respiration declared him dead after he’d been in the ice only 2 minutes. The machine got confused because he hadn’t taken a breath and his resting heart rate was a mere 35 beats per minute. He wasn’t dead, though, and Kamler had to disconnect the device to continue. Hof stayed in the ice for 72 minutes. The results were astounding. Hof’s core temperature initially declined a few degrees but then rose again. It was the first scientific validation of Hof’s method.

“The brain uses a lot of energy on higher functions that are not essential to survival. By focusing his mind, he can channel that energy to generate body heat,” he speculates.

Researchers at Maastricht University in the Netherlands wondered if Hof’s abilities stemmed from a high concentration of mitochondria-rich brown adipose tissue, also known as brown fat. This little-understood tissue can rapidly heat the body when it metabolizes its fuel source: ordinary white fat. Brown fat is what allows infants—who don’t have the muscles to warm themselves like most adults—not to succumb to cold in their earliest months. Usually brown fat mostly disappears by early childhood, but evolutionary biologists believe that early humans may have carried higher concentrations of it to resist extreme environments.

The scientists learned that Hof, then 51, had built up so much brown fat over the course of his training that he could produce five times more heat energy than the typical 20-year-old—most likely because he repeatedly exposed himself to cold.

Brown fat may be the missing organic structure that separates humans from the natural world. White fat stores caloric energy from food, which the body tends to burn only as a last resort. In fact, it’s difficult to burn the spare tire off your waistline because the body is programmed to store energy; even during intense exercise routines the body will completely deplete muscles of energy before it switches to white fat. Brown fat is different. Most people create it automatically when they’re in cold environments by way of a process called beiging. Essentially, the body detects physical extremes and starts to store mitochondria. When brown fat starts to work, the mitochondria suck white fat through the bloodstream and metabolize it directly to generate heat. Because most people do everything they can to avoid environmental extremes, they never bui...

Warm environments are supposed to make me feel warm, but that’s not what is happening. Things are backward. At first a small shiver escapes up my spine. A minute or two later it is a full blown shake. My teeth clatter audibly and soon I can’t remember ever being this cold before in my entire life. This, I will learn later, is what paramedics who rescue hypothermic patients call “afterdrop.”

During vasoconstriction the limbs get much colder than the core. When the body starts to warm up, it lets blood through the vascular system again.

At birth someone who has the mutation for absolute pitch might indeed have the raw potential to become an expert musician, but only with training and concentration can that individual hone the sense for optimal performance. Once trained, that inborn ability becomes “perfect pitch,” a skill and ability prized by musicians. But if left untrained, musical ability can disappear with disuse like a vestigial tail, even when the underlying biology for absolute pitch is still present. A person with such a gift but with no musical inclinations could live their whole life without ever realizing the ability they might have had.

Indeed, Captain Cook—the most famous English explorer of the Pacific and the first European to circumnavigate New Zealand—achieved much of his success with the aid of a Tahitian chief who boarded his ship, the Endeavour. The chief, named Tupaia, sailed with the crew for almost 20 months and used his memories of the waters to help Cook create a map of 130 islands along a 2,500-mile swath of ocean. Much to Cook’s astonishment, no matter where the Endeavor traveled, and despite turbulent conditions, dark of night, or the stillness of a featureless day, Tupaia could always point to the direction of his home island. Tupaia was a wave pilot who could read the minute signatures that land leaves on ocean currents, something he called di lep. Cook, who had the aid of a Royal Navy compass, recorded in his account of his trip that Tupaia was never once wrong with his directional sense.

In the 1970s a biologist at the University of Manchester in England named Robin Baker attempted to test a theory that some humans, like birds, are able to sense direction through the use of an innate cellular compass. The theory was that humans have magnetically sensitive cells in their nasal bones and eyes that can feel the pull of the magnet poles in the same way that compass needles always point north. Baker decided to test the idea by tying magnets to the heads of healthy college male volunteers in order to reorient any magnetic cells to the local interference. He tied nonmagnetic brass bars to the heads of his control group and then drove his blindfolded test subjects into the English wilderness and asked them to point the way home. In his groundbreaking findings, he reported that the nonmagnetized students could point the way home with a significantly higher degree of accuracy than the others. The research set off a flurry of subsequent research, not all of which was able to replicate Baker’s results. Other magnet-tying tests failed. However, after many contentious debates carried out over the course of a decade, researchers reached a consensus that whether the cause was magnetism or some other aspect of underlying biology, humans do indeed have an innate directional sense. It’s just that we don’t use it very much anymore.

I lost my directional sense after just a few short months of depending on a digital knick-knack. Like most people who use their phones to ping their GPS coordinates off of mobile phone towers, I had outsourced my wayfaring abilities from my brain, and maybe the tiny magnets in my nose and eyes, to an electronic gizmo. Culture and technology overtook my biology.

Researchers hooked up cabbies to MRI machines and discovered that the longer they drove cabs, the larger the volume of their hippocampi increased. The finding proved that thinking spatially can drastically change the brain. However, and perhaps more interesting, is that once the drivers retired, their brain structures returned to ordinary sizes.

While digital maps are a fairly recent phenomenon, there are other much more fundamental biological abilities that have simply vanished from our everyday use altogether. They lie there dormant and unused until the right stimulus wakes them up.

The water, it turned out, triggered a series of physical changes in his subjects that advantageously prepared them to survive in a hostile underwater environment where breathing would mean death.

If you happen to be prone to panic attacks, then submerge your face in ice water at the peak of the attack, which will signal your body to prepare for going underwater and disrupt the heart palpitations.

It’s not easy to know how many vestigial responses like these lay dormant deep within our human physiology. They are the sorts of abilities that only manifest themselves when the right conditions arise. They are the gift of millions of generations of incremental biological changes from ancestors whose daily challenges we only have a dim understanding of. Because most humans nowadays live within a narrow band of homeostasis, unlocking new responses occurs mostly by chance. And yet, when they do trigger, we are not always conscious enough to notice how they kicked in. In the modern world there are almost no people who are truly “untouched” by civilization.

While Geronimo’s successes are a rare example of indigenous triumph over the juggernaut of Western progress, there are many tales of native healers and shamans who displayed similar abilities. The nomadic reindeer herders of Norway, the Sami, were said to be able to communicate telepathically with one another over impossible distances. Similar feats show up with certain Aboriginal groups in Australia and among various South American tribes.

Either way, there was surely some contact between us and the Neanderthals, and it appears that the two species mixed and reproduced together.

The invention of technology, as a rule, seems to correlate with a generally weakening of the raw physicality and resilience of our species.

“It was much colder then, and during the time that we didn’t have fire they would have had to eat a lot of raw meat,” Kissel says. “This almost certainly meant that they had some pretty impressive gut bacteria.” If not for resilient guts humans would never have been able to survive on uncooked meat without risking serious illness. Indeed, the fossil record tells us that some of the most obvious skeletal changes occurred in conjunction with cooked food. Richard Wrangham, a biological anthropologist at Harvard, argues that the human jaw started shrinking once we learned how to control fire. Since cooking softens meat and kills potentially harmful bacteria, we no longer needed the pronounced mouths and powerful forward-jutting jaws of our more apelike ancestors.

Homo erectus was different than the great apes that preceded it. Homo erectus walked upright on two feet, and, because digestion takes less time when food is cooked, has a smaller gut than most apes. Over the next million years or so Homo erectus experienced a gentle progression into the more refined human form we now enjoy. Presumably because Homo erectus didn’t have to spend so much time chewing, it could do other things that led to evolutionary pressure that increased reliance on technical skill; therefore, brain size increased. At some point, Homo erectus also lost its body hair, seemingly because he could use fire to keep himself warm at night.

Wrangham’s analysis breaks new scientific ground precisely because he shows that technology has had a profound effect on the human form. In fact, its effect is so strong that it is almost impossible to separate human evolution from cultural and technological changes. To put it another way, the body you have now would not have been possible had we not invented fire. But that doesn’t mean the transitions were always smooth, or, for that matter, fast. At various points, as technology and biology altered course together, when the pace of change was too rapid, we began to suffer from evolutionary mismatches between our outdated biology and the world we were quickly inventing.

The most classic example of an evolutionary mismatch—and an easy one to locate in the fossil record—is the position of our teeth. As the human mouth shrank over time, the number of teeth remained constant. Today, as we grow older, wisdom teeth poke out of our gums and shunt the other teeth ...

Understanding changes in soft tissue that give rise to evolutionary mismatches is a far less straightforward affair. Barring an amazing stroke of luck, like discovering a flash-frozen Neanderthal body in permafrost, there is no definitive way to tell how our muscles, brains, fats, and organs have changed over time. Anthropologists and biologists are stuck making educated guesses about the vast majority of our early biology.

This observation was hardly revolutionary and would have gone unnoticed if he hadn’t also suggested that Neanderthals used brown adipose tissue (BAT), colloquially known as “brown fat,” to keep themselves warm.

Brown fat is a fundamental tissue in mammals that, at the time, was mostly understood as something that rodents used to help heat themselves during hibernation. The spongy, fatty tissue looks a lot like ordinary white fat that most mammals use to store excess caloric energy. But where white fat can serve as an insulator, brown fat has an active role to burn white fat to generate body heat. It’s the only mammalian tissue whose sole purpose is to make heat, or, in scientific terms, thermogenesis. In humans, however, BAT was only considered important in newborns. The very first challenge that a human faces once it is born is the constant fight to keep a stable body temperature. With a relatively high ratio of surface area to body mass, babies lose heat much faster than adults. This is why many premature babies spend their first weeks in incubators.

The easiest way for an adult to rapidly increase their core temperature is through shivering. The activity of muscles generates a moderate amount of heat as a byproduct of movement. Fresh from the womb, infants lack significant musculature and can’t shiver themselves warm. Instead they are usually born with a layer of chubby rolls of insulating white fat. When their core temperature be...

Once the infant becomes a child and its muscles begin to tone up, the white baby fat disappears and along with it the brown adipose tissue. By the time they’re adults, most humans have very little BAT in their system. What does remain is often just a ...