Surviving the Extremes: A Doctor's Journey to the Limits of Human Endurance (24 page)

Jerboas and Tuaregs in the Sahara and desert toads and opal miners in the Australian Outback all go underground to escape the heat. The jerboa, a jumping rodent with long hind legs and a long tale, estivates—a kind of reverse hibernation in which it spends the entire summer safely beneath the surface of the sand. Tuaregs build houses with basements 30 feet deep where they can take refuge when the heat is overwhelming. Australian toads escape the blazing heat of the Outback by burrowing well below the surface. They store water in their bladders and can live underground for years. Opal miners also go underground, using digging machines to carve out enormous caves for themselves and their families. These caves have their own water supply and sometimes even swimming pools. Though the aboveground temperatures can exceed 120°F, their house temperature remains constant at about 75°F. The town the miners founded, Coober Pedy, was given its name by the local aborigines who refer to the place as
kupa piti,
which means “white man in a hole.”

Humans survive mostly by using their nimble brains to adapt the desert to their bodies, yet there are indications that they can also adapt their bodies to the desert, albeit at a much slower pace. Heat sculpts body parts. An obvious example, one that developed in mammals long before there were humans, is the positioning of testicles. Since the sperm cells in testicles cannot tolerate the internal temperature maintained by warm-blooded animals, a thin pouch evolved to hang them
outside the body. Suspended in the scrotum, testicles can be cooled by air flow and, at least in four-legged animals, blocked from the sun’s rays. Humans have actually interfered with this adaptation by standing up and putting on clothes. Clothes retain radiant heat and block convective heat loss, increasing the temperature inside the scrotum. “Civilized” males have disordered cell patterns in their testicles compared to those in males who go naked.

Heat also sculpts body shapes. The geometric shape that has the smallest surface area in proportion to its interior mass is the sphere; if internal heat can be dissipated only at its surface, spheres will retain heat the longest. The shape works well for Eskimos, who tend to have well-rounded bodies. Desert dwellers are better served by a tubular or angular design, providing far more surface area for cooling. People of the African plains, like the Masai and Samburu, who evolved in hot dry climates, are tall with long arms and legs. To favor heat loss further, they have only a thin layer of insulating fat under their skin.

Tall and thin may be good for heat loss, but if there is no place to store fat, it is a dangerous shape in a barren wilderness, whether a desert of sand or of water. The Polynesians’ ability to store fat allowed them to survive long uncertain sea voyages, and desert nomads could use some insurance too. If their body fat were concentrated in one place rather than spread out evenly, it would be readily available for energy production yet still have a minimal insulating effect. Camels have perfected this idea by developing not just long slender legs for heat dissipation but humps in which to store their body fat. Similarly, the long-limbed Hottentots of South Africa are able to store large amounts of fat in their buttocks. A proclivity for depositing fat unevenly remains widespread among humans. In deference to the demands of thermal regulation, tubular areas of high heat exchange—the head, neck, arms, and lower legs—remain mostly free of extra fat. The bulk of it is targeted to the buttocks, thighs, or abdomen, much to the consternation of weight-conscious individuals everywhere.

Besides relocating body parts and remodeling body shapes, heat has a say in selecting body color. Dark skin has always been advantageous for humans in central Africa because it contains more melanin, a pigment that fends off the intense ultraviolet radiation of the equatorial
sun. It gives its wearer protection against sunburn and skin cancer. But darker pigments also retain heat. In tropical areas with plenty of water, the added heat load is neutralized by increased sweating, but for humans who have migrated into arid areas, the advantage of ultraviolet protection is offset by the disadvantage of needing more water to maintain optimum body temperature. Light skin reflects more heat and lowers the water requirement but allows more radiation into the body. Evolution has apparently not yet solved this dilemma; deserts contain people of every skin color. The ideal skin pigment would be one that blocks ultraviolet light yet still allows heat to escape. However, now that humans have invented clothing, skin pigmentation will become irrelevant to evolution. It is easier and quicker to change clothes than to change skin, and just as effective. Natural selection as a driving force of adaptation will be disconnected, and evolutionary improvements will stop.

Human beings are a work in progress, still incompletely adapted to the various environments into which they have ventured but often able to survive there through a combination of animal instincts and intelligence—their own and their culture’s—that trumps their physical shortcomings. Still, how much environmental adversity can an out-of-place, disconnected human overcome? Could instinct and intelligence really have kept Mauro Prosperi alive in the desert for nine days? Prosperi’s story is not unique. A century ago, a prospector named Pablo Valencia survived eight days in the Mojave Desert with one day’s supply of water. He didn’t have civilization, desert wisdom, or even a marathoner’s body, but, like Prosperi, he had animal instinct, human intelligence, and a fierce will to live.

The Mojave is part of a forbidding expanse of desert that runs like a corridor through the southwest United States and into Mexico. For settlers migrating westward, it was the desperately hard final leg of the trail that they encountered as they descended the Rockies. The finish line was the Sierra Nevada mountain range of California, which blocks rainfall from the Pacific and guards the desert. The trail offers no relief until it reaches the far side of the mountains.

One particularly desolate stretch of the trail lay along the southern Arizona territory just a few miles north of the Mexican border, barren
except for occasional cactus and chaparral, with an average temperature over 95°F. The only water to be found consisted of chance remnants of rare rainfall collected in potholes or rock crevices below granite ledges. The route was known as El Camino del Diablo, “The Route of the Devil,” marked nearly every mile by the grave sites of travelers unable to complete their onetime, one-way journey west. Even today the region remains a death trap for migrant workers trying surreptitiously to cross the border from Mexico.

In 1905, in addition to settlers heading for California, there were isolated explorers in the region—among them a naturalist looking for the secrets of desert life, and prospectors looking for gold. W. J. McGee, the director of the Saint Louis Museum, and his Papagos Indian guide, Jose, were camped by a water pool when in rode Pablo Valencia, a Mexican prospector, accompanied by his vaquero guide, Jesus Rios. Valencia was returning to a “lost mine” he said he had rediscovered, and had hired Rios to help him stake a claim. McGee described Rios as sixty-five years old and “claiming familiarity with the country but erratic and inconsequent, and little dependable in any way.” Valencia was “about forty, of remarkably fine and vigorous physique, openly scorning hunger and thirst and boasting ability to withstand far beyond ordinary men the habitual inconveniences of the range.” McGee judged him “lightly burdened with acute sensibility, imagination or other mentality; indeed, an ideal man to endure stressful experience.”

After a day’s rest Valencia and Rios set out on horseback before dawn. Sometime after midnight, Rios came back alone but with both horses, reporting that after riding 35 miles, Valencia had “sent him back to re-water the horses” while Valencia kept a 2-gallon canteen of water and continued ahead on foot into the trackless desert. They had agreed to rendezvous the next day on the far side of some mountain. McGee called it “an inane if not insane” plan.

Rios left the next morning but returned again that evening, declaring that he had been unable to find Valencia. McGee sent out Jose, an expert animal tracker, to look for Valencia, directing him “to go to the limit of his horse’s endurance and then to his own limit beyond.” Jose easily found the trail and followed it through the day and into the night. When his horse became too tired, he continued on
foot until he could go no farther, returning to his horse at dawn and then back to camp where he collapsed in exhaustion. McGee and Jose agreed that any further attempts at rescue, besides being dangerous, would be pointless. Valencia had now been out in the desert over three days with but one day’s supply of water. The naturalist and the Indian were both sure that Valencia was already dead.

Rios rode away, and McGee and Jose uneasily resumed their normal camp routine. Eight days after Valencia’s disappearance they were awakened just before dawn by a strange noise that at first they took to be the bellowing of a lost bull steer. They ran out to investigate and, at the base of a dry gulch, came upon “the wreck of Pablo.” McGee described him as “stark naked; his formerly full-muscled legs and arms were shrunken and scrawny; his ribs ridged out like those of a starving horse; his abdomen was drawn in almost against his vertebral column. . . . His eyes were set in a winkless stare . . . able to distinguish nothing save light and dark.” His ears were “deaf to all but loud sounds. . . . His lips had disappeared” so that “his teeth and gums projected like those of a skinned animal, but his flesh was black and dry as jerky. . . . Even the freshest cuts were as scratches in dry leather without a trace of blood.” In short, McGee provided a very acute description quite similar to the one provided by the military doctors who treated Mauro Prosperi. Both McGee and Prosperi’s doctors estimated that their patients had lost 25 percent of their body weight.

Valencia needed water desperately, but he was unable to swallow, so McGee rubbed water all over his body. At first it rolled off his skin as it would off tanned leather; then the skin began “absorbing it greedily as a dry sponge.” Soon he was able to drink, and in a few hours his circulation was restored enough for him to bleed from his numerous cuts. Blood-borne immune cells were now able to reach his open wounds to fight infections that already had several days’ head start, and McGee observed a rapid and fearful swelling and inflammation of Valencia’s limbs. With the essential ingredient of water, plus some food, all Valencia’s body systems were gradually restored, though McGee reported that the Mexican prospector’s once black hair remained permanently gray. In three days he was well enough to recount his ordeal.

After separating from Rios, Valencia had continued on foot, slept
in the sand, and reached his mining site the next morning. He set about collecting samples and posting notices for a mineral claim, finishing his work before noon. He drank the last of his water shortly after, expecting to rendezvous soon with Rios. When he failed to show, Valencia headed out for a road Rios had described to him. By nightfall he had found neither Rios, nor the road, nor any water. He soothed his dry throat by gargling his urine. The following day he found some trails that led nowhere and an immense pothole, completely dry. Trying to relieve the heat and reduce his weight, Valencia threw away his clothes and even his shoes, keeping only the canteen so that he could save his drops of urine, which he was now drinking.

By the fourth day Valencia became convinced that the trail he was searching for didn’t exist, that Rios had never had any intention of meeting him, and that Rios’s plan all along had been to let the desert kill Valencia and then return to stake the mining claim himself. Valencia rued throwing away his clothes, not so much for the loss of sun protection but because in his pocket was the knife he would have used to stab Jesus Rios. His desire for vengeance became an obsession, giving him the will to continue. He walked in the mornings, rested in the shade of a bush to avoid the afternoon heat, then walked again in the evenings. At sunset he caught flies and spiders and one green scorpion, which, after he ground off its stinger with a stone, yielded a few precious drops of moisture. At last Valencia came across the El Camino del Diablo wagon trail. There were no settlers traveling on it, but he followed the ruts, knowing they would lead back to McGee’s camp. Several times he collapsed on the trail but was inspired to go on by thoughts of Rios and the pleasure he would take in knifing him.

Valencia’s recollection of his final day on the trail was vague except for one experience that he described clearly: as the sun rose that last morning, he died. The sun burned down on his body, but his soul was reluctant to abandon it and hovered over him the whole day. When darkness fell and the desert cooled, he felt a shadow stir his naked body and push it along. Whatever it was lay beyond his control. Just before dawn he was surprised to hear a bellowing noise coming from within his body. He crawled a little farther on and was met by Jose and McGee, who had heard the noise.

Pablo had lived eight days in the desert, seven of them without water other than the few drops he extracted from the scorpion and his recycled urine, which dried up after five days. His survival would seem to be a physiological impossibility, yet, as McGee was to write, “his wrath spurred him on—a potent incentive which carried him miles and doubtless saved his life.”

Valencia was convinced he died on the last day though his body kept going, not even losing its trail sense. Did his out-of-body experience represent a disconnect of his cerebral cortex, taking away his will? At the moment his endurance reached its limit, did his higher functions relinquish control, diverting it to the lower brain in order to save power? It seems Valencia was able to energize his most basic animal instincts for a last desperate, and successful, attempt to save himself.

Pablo Valencia was conditioned to the desert. He was a hardened prospector, physically fit, and powered by vengeance. Mauro Prosperi was a world-class endurance runner, acclimated to the heat, inured to physical hardships through years of training and discipline. Each man was able to deploy a fine-tuned body defense and activate a fierce will to survive, adding human intelligence to latent animal instincts.