I was so impressed that I decided to watch another Chinese Tibetan propaganda film. I have forgotten the name, but it was about a group of Chinese Possum Cops led by a Tibetan turncoat who hunt down and kill a band of peasant poachers who are after Chiru antelope. The scenes are harrowing, instead of happy kids at play in wildflower meadows, it is high altitude hell where everybody's fingers fall off and nobody can breathe. The goal is to show how horrible Tibet and Tibetans are, and how enviros ought to support the Chinese who are clearly superior to the benighted greedy superstitious fuzzy bunny killing peasants. If the reality of Tibet is even remotely similar to the frozen wasteland shown in the flick then you can cancel my reservation!
How interesting that Han Chinese government propaganda would depict the Tibetans as ill-adapted to their high altitude environment, when a recent genomic study has shown that indeed the residents of the Tibetan plateau are the only human population that has evolved to adapt to such an environment. This study was recently published in the journal Science ("Sequencing of 50 Human Exomes Reveals Adaptation to High Altitude" Science 2 July 2010: Vol. 329. no. 5987, pp. 75 - 78, DOI: 10.1126/science.1190371--many of the authors are Chinese).
The gist of the article is as follows: The Tibetan plateau has been inhabited for around 25,000 years. It has long been observed that people who are not native to elevations higher than 4,000 meters respond to the lower concentration of oxygen at high altitude by synthesizing a much larger number of red blood cells in order to increase their hemoglobin concentration (the well-known "natural blood doping effect"). This creates complications due to increased blood viscosity, and can actually compromise transfer of oxygen from hemoglobin to peripheral tissues. Native Tibetans do not display an increased number of red blood cells, and actually appear to have a similar number of red blood cells as people who reside at sea level. How is this possible? The researchers found that multiple proteins in a signaling pathway related to response to hypoxia (low oxygen) were mutated to facilitate transfer of oxygen from hemoglobin to the peripheral tissues at the reduced oxygen conditions found at high elevations. Hence no need for extra red blood cells! The estimated rate of mutations in the genes in this pathway is a faster rate of change than previously observed for any human gene, and the authors say this represents the strongest instance of natural selection seen to date in the human population. Also, populations that reside at high altitude in the Andes do not show the same changes, probably because they haven't lived at high altitude for as long as the Tibetans.
The authors didn't address the question that immediately jumped to my mind: what happens to Tibetans when they go to sea level? Do they lose red blood cells?
Diana * * * * * * * * * * * * * * * * * * * * * * * * * * * * Diana R. Tomchick Associate Professor University of Texas Southwestern Medical Center Department of Biochemistry 5323 Harry Hines Blvd. Rm. ND10.214B Dallas, TX 75390-8816, U.S.A. Email: [email protected] 214-645-6383 (phone) 214-645-6353 (fax) --------------------------------------------------------------------- Visit our website: http://texascavers.com To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
