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Mouthful of air

Santanu Chakraborty | Updated on May 08, 2020 Published on May 08, 2020

Peak challenge: The Himalayas became the focus of mountaineers in the late-19th and early-20th centuries ISTOCK.COM   -  Getty Images/iStockphoto

Mountaineers have to deal with intense oxygen deprivation yet remain supremely athletic. How does the human body deal with this challenge?

The imposing mountains have always evoked a primal fear as well as an enduring fascination in humans. Despite the physical hardships high altitude brings on, humans have made their homes in the great mountain ranges of the Earth since the beginning. But only a few have attempted to climb atop the highest peaks.

Mountaineering as a serious pursuit took off in Europe in the 18th and 19th centuries and was shaped by the many attempts at climbing Mont Blanc and the Matterhorn, the most difficult peaks on the Alps. That these pursuits were quite popular is clear when one considers the fact that the first party to successfully climb the Matterhorn — a sharp, steep, pyramidal giant in the Alps between Italy and Switzerland — was led in 1865 by Edward Whymper, an artist and illustrator from England.

Popular interest in mountaineering soared after the first alpine ascents, and mountaineers garnered immense popularity. Not every European, though, could afford these expeditions, but many would attempt to climb the alpine peaks in a minimalist manner, carrying their own loads and learning to walk and climb freely on the mountain without using ropes for support.

By the late-19th and early-20th centuries, mountaineers turned their attention to the Himalayas, then considered the last great unclimbed mountain range with peaks rising 8,000m above sea level. The treacherous ranges continued to defy human attempts to conquer them for a long time.

Mountaineers began attempts to scale the great Himalayan peaks only to be confronted by challenges that existed at a greater scale than anywhere else on Earth. Those climbing it Alpine style — with minimum technological support — tried to do so without any bottled oxygen. In order to understand how difficult this aim was, consider this: People who land in the city of Leh and start walking, at an altitude of 3,500m, often immediately begin to experience trouble breathing. Now imagine what it takes to trek to the foot of a great mountain, carrying heavy loads, set up base camp and, over the course of a month or more, attempt to climb beyond 8,000m on low oxygen and in biting cold. Such an expedition drains every ounce of strength and exhausts one’s oxygen-gathering capacity, for, on top of the highest mountain on Earth, there is very little oxygen — only one-third the amount available at sea level. Mountaineers have to grapple with two challenging conditions — they need to be intensely athletic even while dealing with extreme oxygen deprivation, which is akin to running a marathon while partially choking. Expeditions to the Himalayan peaks require endurance that only a few can muster.

So scientists have striven for insights into the physiology of humans at high altitude and low temperatures. Anecdotal evidence suggests that the Sherpas, a community from Nepal, as well as Tibetans can operate effortlessly at altitudes that would leave those from the plains gasping. Modern technologies allow us to measure metabolic and physiological indicators with precision. Modern genetics, with its molecular and computational tools, makes it possible to sequence the genome of a human in about $1,000. As early as 1965, scientists had deduced that Sherpas used oxygen more efficiently at the level of a single cell. Studies since have shed light on the selective pressures that operate in highlander communities due to the continuous exposure to an extreme environment. Now biologists who study evolution are hardly surprised by the discovery of unique genetic signatures which helpin adaptation to low-oxygen environments in highlander populations. It turns out that certain versions of at least three different genes are found more often in Sherpas and those with Tibetan descent, one of which (a gene called EPAS1) appears to be the result of a partial descent from Denisovans, a species of extinct humans whose remains were first found in a Siberian cave.

Transgenic mice with similar gene alterations were studied to understand the interaction of low-oxygen environments with these genes. Versions of another gene — PPARA — found in highlanders allow them to metabolise fuels such as sugars more efficiently. They can turn food into fuel faster and reduce the wasting away of the body at high altitude, where certain fats stored in muscle, liver and other organs are rapidly cannibalised for survival. There are multiple pathways of fatty acid metabolism in the body and scientists speculate that the Sherpas have specialised genetics that allow them to switch to a different form of fat burning that may be less fatigue-inducing in the muscles.

While a great deal of work continues on the mechanisms of extreme athleticism under low-oxygen and low-temperature environments in humans, some scientists have chosen to study animals that demonstrate feats of endurance that not even the strongest humans can achieve. Of particular interest are bar-headed geese, which migrate from Mongolia to South India, flying over the great Himalayan peaks and valleys at over 5,000m altitude. That almost all these birds can achieve such feats of endurance, constantly using their muscles instead of gliding over headwinds, suggests massive adaptations over evolution. These cellular, metabolic and genetic adaptations are today being studied at the molecular level by scientists around the world.

And yet genetics is not all. Peter Habeler and Reinhold Messner did the unthinkable in 1978 by scaling Mount Everest, standing tall at 8,848m, without any supplemental oxygen; the first humans — and lowlanders to boot — to achieve such a feat. Perhaps determination, training and human will can still overcome the limitations of our selves. Or so one hopes.

Santanu Chakraborty   -  BUSINESS LINE

 

Santanu Chakraborty is a Bengaluru-based engineer, scientist and photographer

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Published on May 08, 2020
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