Surviving the Extremes: A Doctor's Journey to the Limits of Human Endurance Read Online Free

high seas, dense jungles, tall mountains, and outer space were all safely inaccessible, so the challenge to adapt to more extreme conditions simply did not exist. With gradual exposure over enough generations, humans demonstrate enormous adaptability. Without that exposure, such remote regions are deadly.
    With no one willing or able to go there, forbidding environments long remained empty spots on the map. Advancing technology, however, has suddenly made these places accessible. Moreover, the peculiarities of modern civilization have made them alluring to explorers, scientists, and adventurers. In an evolutionary instant the rules have changed, though the game—survival—remains the same. For example, the body “understands” tiger bites; it doesn’t “understand” nitrogen bubbles. It knows the rules for tigers because it has been dealing with them for thousands of years. Through trial and error, natural selection has equipped humans with a complex and precise sequence of physiological responses, refined over countless generations, whose aims are to counteract a tiger’s predation. First, the mind recognizes that the fast-approaching creature is dangerous; then it sends a signal to the body, instructing it to flee. Should the escape mechanism not work, the body prepares to defend itself. And if it gets injured, there is a preset sequence of healing cells and chemicals that can assess the damage and initiate repairs. The effort may prove unsuccessful, but the body understands the threat and has developed the tools that enable it to fight.
    What happens to the same meticulously developed defenses when nitrogen bubbles attack the body? Deep-sea diving has only beenaround for a few generations, and exposure, when it occurs, is anything but gradual. In the body of a diver, the bends, the onslaught of nitrogen bubbles in the bloodstream, is like an alien invader. Having never seen it before, and with no time to adapt, the body’s response will be as chaotic and misdirected as planet Earth’s reaction would be to an attack from Mars. The body undertakes equally chaotic responses to other unfamiliar enemies: the low air pressure on a Himalayan mountain or the high water pressure under the ocean; the constant daylight of a polar summer or the constant darkness and extreme cold of a polar winter; the relentless heat in an African desert; the weightlessness of outer space. Yet, as we will see, people who live on or near extreme environments—from jungle Indians to Sherpas, from Eskimos to Bedouins to South Sea pearl divers—have each developed specific adaptations to the environmental insults they confront every day. Evolution has molded humans to fit along the various frontiers of survival, but even their special protection breaks down quickly if they push themselves beyond their borders.
     
    Pasang should not have survived, but he did. Over the course of the night, his thready pulse strengthened, the swelling in his face receded, and he opened his eyes. With the morning light, the chanting stopped and the spell was broken. Though I felt I had been watching the scene from afar, I was certain I had witnessed a healing force that was beyond medicine. The chanting had released an energy within Pasang, a will to live, and this had reversed his decline. A spiritual force had created a tangible effect, what a religious person would call a miracle. My medical training should have led me to explain his recovery in terms of nerve impulses and chemical reactions, but confronted with such incontrovertible testimony high on a Himalayan mountain, even a faithless man believes. There was no medical reason for Pasang to be alive. I realized then, that practicing extreme medicine would sometimes mean witnessing, and working alongside, phenomena I might never understand.
    A rescue helicopter was on its way and we had to get the patient ready to go. I busied myself with the details of an evacuation that,last night, I was sure wouldn’t be