Life On Top of the World

Mt Everest stand at 29,029 ft above sea level as is in an area of the Himalayas bordering the Tibetan Plateau.  The air is 40% thinner than at sea level and so the human body must adapt in order to survive. Many people attempting to summit Mt Everest develop altitude sickness and don’t make it past base camp, yet native Tibetans live on the Tibetan Plateau at almost 15,000 ft above sea level with little issue. When a human moves from low-altitude to high-altitude usually the body copes with the lack of oxygen in the air by increasing the number of red blood cells in the body so that more oxygen can be carried.  The downside of this tactic is that blood becomes thicker and there is an increased risk of heart attacks or strokes as the heart works harder to pump the more viscous blood around the body. Native Tibetans who were born and spend all their life at high altitude don’t have a higher red blood cell count, instead they have adapted to use a regular red blood cell count and their thinner blood reduces the risks and side effects most low-altitude dwellers people experience when they move to high- altitude. For this unusual trait, the Tibetans have their ancestors to thank.  Recent studies have found that Denisovans (genetic cousins of Homo Sapiens), an ancestor of the modern day human, possessed the EPAS1 gene that had evolved to cope with life at high altitudes.  This was passed to modern day Tibetans most likely through interbreeding of Denisovans with other archaic human societies around 40,000 years ago.  The way this gene works, and why the Tibetans can survive without the need to increase the number of red blood cells in their body is still unclear, but it makes you wonder what other secrets are held in our DNA.

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