tag:blogger.com,1999:blog-7785493.post8369447748847630571..comments2024-01-04T04:11:55.717+02:00Comments on Dienekes’ Anthropology Blog: Recent Tibetan adaptation for high altitudeDienekeshttp://www.blogger.com/profile/02082684850093948970noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-7785493.post-86604180727996052712010-07-09T20:30:48.453+03:002010-07-09T20:30:48.453+03:00John Hawks has extended correspondence with the au...John Hawks has extended correspondence with the authors on his blog:<br /><br />http://johnhawks.net/weblog/topics/evolution/recent/tibet-nielsen-comment-2010.htmlAndrew Oh-Willekehttps://www.blogger.com/profile/02537151821869153861noreply@blogger.comtag:blogger.com,1999:blog-7785493.post-24268215498336585952010-07-09T20:09:49.696+03:002010-07-09T20:09:49.696+03:00The 3000 years ago date appears to be a mutation r...The 3000 years ago date appears to be a mutation rate date, and hence, subject to error bars that are huge relevant to the pre-history and early historical dates that matter to people trying to get the story of East Asian origins straight.<br /><br />The overall similarity of Han and Tibetan genomes in non-adaptive traits supports the linguistic and archeological indications of the relatively recent common origins of the groups.<br /><br />More relevant that the estimated date itself is the sequencing of the split that it implies. <b>This study shows that the Han broke off from the Tibetans before the Tibetans made selective adaptations to high altitude.</b> Genetic drift out of a high near current Tibetan population levels frequency of a no longer necessary high altitude oxygen processing allele would not have happened fast enough for it to be as rare as it is now in the Han Chinese population.<br /><br />Thus, rather than being a Tibeto-Burmese urheimat, as an examination of linguistic diversity might suggest, Tibet looks more like a mountain refugia from a true homeland for the language family. This would put a Tibeto-Burman linguistic homeland not in the headwaters of the Yellow River, but further downstream, at Lanzhou or further East.<br /><br />Since it is fair to guess, selective pressure on proto-Tibetans to adapt to high altitude would have been early and intense. Babies born without these adaptations are far less likely to survive to have children of there own. Even if half a dozen generations, an adaptation of this extreme level of adaptive benefit would become dramatically more frequent. It would probably have taken hold more rapidly than lactose tolerance, for example.Andrew Oh-Willekehttps://www.blogger.com/profile/02537151821869153861noreply@blogger.comtag:blogger.com,1999:blog-7785493.post-43900004478869889722010-07-02T10:34:09.983+03:002010-07-02T10:34:09.983+03:00Interestingly, Razib also discusses the age issue ...Interestingly, Razib also discusses the age issue in his thread about the same study: <br /><br />http://blogs.discovermagazine.com/gnxp/2010/07/very-recent-altitude-adaptation-in-tibet/#more-4684Onur Dincerhttps://www.blogger.com/profile/05041378853428912894noreply@blogger.comtag:blogger.com,1999:blog-7785493.post-84976886134056228272010-07-02T10:20:19.569+03:002010-07-02T10:20:19.569+03:00How do they know the age of the genetic change? Hu...How do they know the age of the genetic change? Humans inhabited the Tibetan Plateau since Pelaeolithic times. Language relationships do not prove anything.Onur Dincerhttps://www.blogger.com/profile/05041378853428912894noreply@blogger.com