Introduction An Ode to a Jellyfish I don't like to suffer. Nor do I particularly want to be cold, wet, or hungry. If I had a spirit animal it would probably be a jellyfish floating in an ocean of perpetual comfort. Every now and then I'd snack on some passing phytoplankton, or whatever it is that jellyfish snack on, and I'd use the tidal forces of the ocean to keep me at the optimal depth. If I were lucky enough to have come into the world as a Turritopsis dohrnii , the so-called "immortal jellyfish," then I wouldn't even have to worry about death. When my last days approached, I could simply shrivel into a ball of goo and reemerge a few hours later as a freshly minted juvenile version of myself. Yes, it would be awesome to be a jellyfish. Unfortunately, as it turns out, I am not an amorphous blob of seagoop. As a human I am merely the most recent iteration of several hundred million years of evolutionary development from the time we were all just muck in a primordial soup. Most of those previous generations had it pretty rough. There were predators to outwit, famines to endure, species-ending cataclysms to evade, and an ever-changing struggle to survive in outright hostile environments. And, let's be real, most of those would-be ancestors died along the way without passing on their genes. Evolution is a continual battle waged through generations of minute mutations where only particularly fit or lucky creatures outperform hapless genetic dead ends. The body we have today hasn't stopped evolving, but I still think if we peel back all the eons of changes that brought us here today that we will still find a little bit of jellyfish at the very core of our beings. This is because we have a nervous system that is almost perfectly attenuated for homeostasis: the effortless state where the environment meets every physical need. Our nervous system automatically responds to challenges in the world around us--triggering muscle contractions, releasing hormones, modulating body temperature, and performing a million other tasks that give us an edge in a particular moment. But barring an urgent need for survival the human body is perfectly content to simply rest and do nothing. Doing things, doing anything, requires a certain amount of energy, and our bodies would rather save up that energy just in case they need it later. The great bulk of these bodily functions lie just beneath our conscious thoughts, but if whatever motivates our nervous system could express itself, it would probably maintain that the body that it is responsible for would best tick by admirably well in a state of perpetual and stressless comfort. But what is comfort? It's not really a feeling as much as it is an absence of things that aren't comfortable. Our species might never have survived necessary but arduous treks across scorching deserts or over frigid mountain peaks if there weren't the promise of some physical reward at the end of the journey. We sate our thirst, don layers of clothing on cold winter days, and clean our bodies because that yearning for comfort is hardwired into our brains. It's what Freud called the "pleasure principle." The programming that makes us gluttons for the easy life didn't emerge out of nowhere. Aside from my jellyfish spirit animal, almost every organism struggles against the environment that it inhabits. Every biological adaptation that makes life incrementally easier came through the glacial progress of natural selection, when two animals were able to pass favorable traits onto their descendants. Yet evolution requires more than a biological duty that culminates in a moment of intense passion; it needs the cumulative luck, motivations, and skill of individual creatures to use their biological abilities to the fullest. Every creature, whether it is an amoeba or a great ape, needs motivation to overcome the challenges of the world around it. Comfort and pleasure are the two most powerful and immediate rewards that exist. Anatomically modern humans have lived on the planet for almost 200,000 years. That means your officemate who sits on a rolling chair beneath fluorescent lights all day has pretty much the same basic body as the prehistoric caveman who made spear points out of flint to hunt antelope. To get from there to here humans faced countless challenges as we fled predators, froze in snowstorms, sought shelter from the rain, hunted and gathered our food, and continued breathing despite suffocating heat. Until very recently there was never a time when comfort could be taken for granted--there was always a balance between the effort we expended and the downtime we earned. For the bulk of that time we managed these feats without even a shred of what anyone today would consider modern technology. Instead, we had to be strong to survive. If your pasty-skinned officemate had the ability to travel back in time and meet one of his prehistoric ancestors it would be a very bad idea for him to challenge that caveman to a footrace or a wrestling match. Over the course of hundreds of thousands of years humans invented some things that made life easier--fire, cooking, stone tools, fur skins, and foot bindings--but we were still largely at the mercy of nature. About 5,000 years ago, at the dawn of recorded history, things got a little easier still as we domesticated various animal species to do work for us, built better shelters, and carried more sophisticated gear. As human culture advanced at least it all was getting incrementally easier. Even so, being a human was not exactly carefree. Each age let us depend more on our ingenuity and less on our basic biology until technological progress was poised to outpace evolution itself. And then, sometime in the early 1900s, our technological prowess became so powerful that it broke our fundamental biological links to the world around us. Indoor plumbing, heating systems, grocery stores, cars, and electric lighting now let us control and fine-tune our environment so thoroughly that many of us can live in what amounts to a perpetual state of homeostasis. It doesn't matter what the weather is like outside--scorching heat, blizzards, thunderstorms, or just fine summer days--a person can wake up long past when the sun rises, eat a breakfast chock-full of fruits flown in from a climate halfway across the globe, head to work in a temperature-controlled car, spend the day in an office, and come home without ever feeling the outside air for more than a few minutes. Modern humans are the very first species since the jellyfish that can almost completely ignore their natural obstacles to survival. Yet comfort's golden age has a hidden dark side. While we can imagine what a difficult environment might feel like, very few of us routinely experience the stresses of our forebears. With no challenge to overcome, frontier to press, or threat to flee from, the humans of this millennium are overstuffed, overheated, and understimulated. The struggles of us privileged denizens of the developed world--getting a job, funding a retirement, getting kids into a good school, posting the exactly right social media update--pale in comparison to the daily threats of death or deprivation that our ancestors faced. Despite this apparent victory, success over the natural world hasn't made our bodies stronger. Quite the opposite, in fact: Effortless comfort has made us fat, lazy, and increasingly in ill health. The developed world--and, for that matter, much of the developing world--no longer suffers from diseases of deficiency. Instead we get the diseases of excess. This century has seen an explosion of obesity, diabetes, chronic pain, hypertension, and even a resurgence of gout. Countless millions of people suffer from autoimmune ailments--from arthritis to allergies, and from lupus to Crohn's and Parkinson's disease--where the body literally attacks itself. It is almost as if there are so few external threats to contend with that all our stored energy instead wreaks havoc on our insides. There is a growing consensus among many scientists and athletes that humans were not built for eternal and effortless homeostasis. Evolution made us seek comfort because comfort was never the norm. Human biology needs stress--not the sort of stress that damages muscle, gets us eaten by a bear, or degrades our physiques--but the sort of environmental and physical oscillations that invigorates our nervous systems. We've been honed over millennia to adapt to an ever-changing environment. Those fluctuations are ingrained in our physiology in countless ways that are, for the most part, unconnected to our conscious minds. Muscles, organs, nerves, fat tissue, and hormones all respond and change because of input they get from the outside world. Critically, some external signals set off a cascade of physiological responses that skip the conscious parts of our brains and connect to a place that controls a wellspring of hidden physical reactions called collectively fight-or-flight responses. For example, 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. A person actually has to get uncomfortable and experience that frigid cold if they want to initiate those systems. But who wants to do that? The bulk of us don't see environmental stress in the same light as we do, say, exercise. There doesn't seem to be an obvious reason to leave our shells of environmental bliss. Maybe that's not entirely fair. In recent years a counterculture has tried to push back against technological overzealousness to reclaim some of our animal nature. They've shucked fancy footwear for flat shoes (and some cases no shoes at all). They've turned away from climate-controlled exercise gyms in favor of rough obstacle courses and boot camps that force muscle groups to work in unison. They're hacking their diets: eating tubers and meat and foregoing grains reminiscent of our Paleolithic ancestors. At least eight million people have bought a product called the Squatty Potty, a device for the toilet to help a person poop in a squatting stance like our pre-toileted forebears did. Millions more sign up for obstacle course races that feature electrified grids, pools of freezing water, and grueling climbs over wooden barriers. They compete until they are so bone tired that their muscles shake. They puke in the mud with tears in their eyes. It's not exhilaration they're seeking: it's suffering. Their pain is so much on the forefront of the experience that the industry of obstacle courses and boot camps are sometimes called "sufferfests." Think about that for a second: There are companies out there that literally make fortunes by selling suffering. How did pain become a luxury good? Could it be that there is a specific sort of pain that might serve a hidden evolutionary function? It would be wrong to call this movement a fad. To some degree there have always been people who have straddled the line between biology and technology. In ancient Sparta, soldier-scholars wore only simple red cloaks and no shoes, regardless of the weather. They believed exposure made them fiercer in battle and immune to the ravages of the outside world. For almost a thousand years in China and Tibet, mystics and monks endured months or even years on Himalayan peaks with just their robes and daily meditations to protect them. Before Europeans arrived in North America, the natives of what is today the city of Boston wore little more than loin cloths to protect them during the icy winters. In the 1920s in Russia, a movement born from religious fervor convinced hundreds of thousands of Siberians to pour cold water on themselves every day in order to stave off infections and illnesses. Advanced technology permeates everything we do, but the people who decide to abandon some of that comfort for the rawness of nature represent an indigenous ethos that has almost been wiped out by a societal desire for comfort. They're learning that if they embrace the way their bodies respond to the natural world, they can unlock a hidden wellspring of animal strength. Today tens of thousands of people are discovering that the environment contains hidden tools for hacking the nervous system. But no matter what they might be able to accomplish, they're not superhuman. The fortitude they find comes from within the body itself. When they forego a few creature comforts and delve more deeply into their own biology they're becoming more human. For at least half a century the conventional wisdom about maintaining good physical health has rested on the twin pillars of diet and exercise. While those are no doubt vital, there's an equally important, but completely ignored, third pillar. And what's more? By incorporating environmental training into your daily routine, you will achieve big results in very little time. It only takes a matter of weeks for the human body to acclimatize to a dazzling array of conditions. Once you arrive at high altitude, your body automatically produces more red blood cells to compensate for lower oxygen saturation. Move to an oppressively hot environment and your body will sweat out fewer salts over time and produce lower volumes of urine. Heat will also stimulate your cardiovascular system to become more efficient and increase evaporation and cooling. Yet no environmental extreme induces as many changes in human physiology as the cold does. Imagine, if you will, a native Bostonian's experience in the winter. Though beset by ice storms, sleet, blizzards, and constant overcast skies, Boston is not the coldest city in America. But the Boston winters are sufficiently miserable to motivate most of its population to head indoors and jack up the thermostat in the colder months. In Boston, the mean difference between the indoor temperature and the outside air in January is a shiver-inducing 39 degrees. When this typical Bostonian walks out the front door of her stately brownstone she probably cringes with pain as a blast of icy air quickens her nerves and turns her face into a grimace. Beneath the surface of her skin a series of nerve and muscle responses cause the blood vessels to constrict, which can be painful if the underlying muscles haven't been strengthened from repeated prior exposures. If, in a fit of uncharacteristic madness, she decides to remove her shoes and plant her bare feet in the snow, the almost 70-degree swing in temperature would feel akin to walking across a hot bed of coals. These unhabituated responses of the human body are not pleasant, but the physiology of the process is worth examining. The human circulatory system is made up of a series of spongy arteries and veins that carry our blood supply (and oxygen) to every tissue. Arteries carry red, oxygen-rich blood away from the heart and lungs while blue-tinged veins carry it back. This vast and complex network of vessels would extend more than 60,000 miles if laid end to end. In a single day, the 5.6 liters of blood in a human body travels a total of almost 12,000 miles through the system, or almost four times the distance across the United States. This great blood superhighway is more than just a series of tubes; it's an active and responsive system. Lining most of the important veins is a similarly complex network of tiny muscles that constrict the flow of blood away from one particular area to boost the supply to another. These muscles are so strong that if someone were to cut off your leg with a sword below the knee, the muscles would immediately clench shut with enough force to almost completely stem the loss of blood. That, luckily, is not the sort of muscular reflex that we need to test on a daily basis, but it's nice to know it's there just in case. However, the second our intrepid Bostonian opens the door to her house and has a brush with that near-Arctic wind, she feels a miniature version of that reaction. Excerpted from What Doesn't Kill Us: How Freezing Water, Extreme Altitude, and Environmental Conditioning Will Renew Our Lost Evolutionary Strength by Scott Carney All rights reserved by the original copyright owners. Excerpts are provided for display purposes only and may not be reproduced, reprinted or distributed without the written permission of the publisher.
