tag:blogger.com,1999:blog-8304928500646903522.post1337314839635764145..comments2024-03-28T00:11:33.489-04:00Comments on bensozia: Denisovan Jawbone Found in TibetJohnhttp://www.blogger.com/profile/01037215533094998996noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-8304928500646903522.post-27973348600823912182019-05-03T21:41:12.101-04:002019-05-03T21:41:12.101-04:00It seems to work in concert with other factors:
W...It seems to work in concert with other factors:<br /><br />Wikipedia (section on Tibetans)-"The genes (EPAS1, EGLN1, and PPARA) function in concert with another gene named hypoxia inducible factors (HIF), which in turn is a principal regulator of red blood cell production (erythropoiesis) in response to oxygen metabolism.[58][59][60] The genes are associated not only with decreased haemoglobin levels, but also in regulating energy metabolism."<br /><br />https://en.wikipedia.org/wiki/High-altitude_adaptation_in_humans#Tibetans_2<br /><br />May 1, 2019 at 9:14 PM<br />Kpgooghttps://www.blogger.com/profile/00270609696502839431noreply@blogger.comtag:blogger.com,1999:blog-8304928500646903522.post-43296042374214507122019-05-01T23:47:34.461-04:002019-05-01T23:47:34.461-04:00Don't ask my why having less haemoglobin helps...<i>Don't ask my why having less haemoglobin helps you survive with less oxygen, but wikipedia's article about EPAS1 says the same thing, so there it is.</i><br /><br />A quick bit of Googling confirms what intuition tells us - less hemoglobin does NOT, by itself, help you survive with less oxygen.<br /><br />When under the effects of hypoxia, the human body produces MORE hemoglobin, not less. This (along with certain other changes) helps oxygen saturation in the blood to be maintained at roughly the same levels.<br /><br />The effect is most pronounced when first moving to higher elevation, and after a few weeks it begins to wear off, but it does level out at higher than normal concentrations while at higher elevation. And it is firmly established that people living at high altitudes have more hemoglobin than those who live at sea level.<br /><br />That said, as with most things, too much hemoglobin actually causes problems. With not enough plasma in the blood compared to red blood cells, the blood becomes thicker and more viscous, raising blood pressure and making pumping it around the body more difficult, which can cause chronic mountain sickness.<br /><br />From what I'm reading, it appears highland Tibetans - despite having higher than normal hemoglobin levels - actually have lower levels than other ethnic groups living in the same region, in particular Han individuals whose genomes originate from lower altitudes.<br /><br />The supposition seems to be that the Tibetans have lower relative hemoglobin levels because their bodies have adapted to cope with hypoxia in other ways. It seems that rather than just continuing to increase the raw amounts of oxygen available to the body via hemoglobin (and causing major health problems in doing so), instead their organs and muscles developed to make more efficient usage of the oxygen available.<br /><br />As I understand it, the effect seems to be somewhat comparable to the ability of certain aquatic / oceanic species to hold their breaths for very long periods.<br /><br />Dolphins, for example, don't have larger lungs (relative to total size) compared to other species - their lungs are just vastly more efficient at gas exchange, and they can extract a far greater percentage of oxygen out of the same volume of held air. Additionally, when diving they actually greatly reduce blood flow to certain non-critical parts of the body, in order to drastically slow their overall consumption of oxygen. They aren't packing more total oxygen into their bodies, they just make much more efficient usage of it.<br /><br />The same underlying principle seems to be at work with Tibetans and other high altitude peoples. They don't rely on more hemoglobin to increase the amount of oxygen in their systems - they instead have systems that have adapted to use less total oxygen, more efficiently.<br /><br />The rest of us don't have those adaptations, and so our only way of coping with hypoxia is to create tons more hemoglobin, but that comes with its own problems, which Tibetans and others manage to entirely avoid.G. Verlorennoreply@blogger.com