Tibetans handle high altitudes much better than most people. New research pinpoints the genes that allow them to breathe easily on mountain peaks, and avoid deadly side-effects.
The people of Tibet are essentially Fremen of the heights. Evolutionary pressure has created a population of people that have a distinct set of physiological traits that help with the dangers of high altitude: decreased arterial oxygen content (low levels of oxygen in the blood), increased resting ventilation (rapid breathing while resting), lack of hypoxic pulmonary vasoconstriction (meaning blood vessels don't constrict when oxygen content of the blood is low), lower incidence of reduced birth weight, and reduced hemoglobin concentration (hemoglobin is a protein in red blood cells that helps transport oxygen from lungs or gills to the body). Put together, this means that Tibetans have evolved to function with far less oxygen in their blood than other people - perfect for high altitudes with low oxygen.
A new study focuses on this final trait, the reduced hemoglobin concentration. Tibetans have 3.6 grams per deciliter less hemoglobin than other populations. When you go up to the insane altitudes that mountain climbers tend to go for, your body ramps up red blood cell production in order to compensate for the low levels of oxygen. This is why athletes train at high altitude — to get more red blood cells into their system, and transfer oxygen around more efficiently. However, a side effect of this increase is the that your blood increases in viscosity. When it gets really bad, your body is pushing around blood the density of motor oil, something it's not designed to do. By naturally having much lower hemoglobin levels, people from Tibet (and assumedly Nepal, and other regions in the area) maintain proper blood fluidity.
While researchers have known about these beneficial mutations for a while, the question remained as to how they worked, and their genetic cause. This new study could help us understand human response to high altitudes, and related physical difficulties. Plus, you know, genetically engineering a race of super-beings for invading K'un-L'un.
By comparing genomic variation between Tibetans, Han Chinese, and Japanese, the researchers from the University of Utah School of Medicine and the Research Center for High Altitude Medicine in China were able to identify the variant genes responsible for the change. There was a strong association between the low levels of hemoglobin and haplotype variation at EGLN1 and PPARA. The variation of these allele loci is what's thought to give Tibetans their low levels of Hb, and help them survive at incredibly high altitudes.
In other words: Suck it, Sir Edmund Hillary.
Paper published in Science