Altitude sickness is caused as a decrease in air pressure affects the body's ability to take up oxygen (although the exact causes are not completely understood). The effects are more severe in those unacclimatised to high-altitude conditions. People who have lived all their lives in such conditions are, understandable, less affected. Mountaineers can also spend time at a high-altitude base camp to acclimatise before making the final assent.
Those who live in the mountainous regions of Earth, generation after generation, have the possibility of adapting to the conditions on a more permanent, genetic bases. Altitude sickness can be debilitating and is occasionally fatal so mutations that allow more effective delivery of oxygen will be favoured. Researchers have now found evidence of such mutations in the high-altitude populations of Tibet.
By taking genetic samples of about 30 villagers and subjecting them to single nucleotide polymorphism (SNP) analysis looking for single base changes in crucial genes. By comparing these SNPs to those from a nearby, low-altitude village 10 candidate genes were identified - including two related to haemoglobin. More work needs to be done to understand how (or if) these gene mutations contribute to survival at high-altitudes but it is certainly suggestive evidence that humans evolve too.
Genetic Evidence for High-Altitude Adaptation in Tibet Tatum. S. Simonson, Yingzhong Yang, Chad D. Huff, Haixia Yun, Ga Qin, David J. Witherspoon, et al. Science, 13 May 2010 DOI: 10.1126/science.1189406
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