A novel mechanism for getting high

There is a new paper out that finds that Tibetans are the product of admixture between a Han-like population and a Sherpa-like population – and that the altitude-adaptive alleles come from the Sherpa side,  which split from the Han a long time ago (20-40k years) and have likely been living at high altitude for a long time.  The admixture was a few thousand years ago.  Last year, I talked about an article in MBE in that came to similar conclusions – but this new paper has gone farther, identifying the population source for these adaptive alleles.  At least, they were the immediate source…

This is contrast to Rasmus Nielsen’s earlier paper, in which he argued that Tibetans and Han split about 3,000 years ago, and that the Tibetan altitude adaptations arose in that relatively short time frame.  I thought that was obviously wrong, since the Tibetan adaptations work so much better than those in Andean Indians – and since there is archaeological evidence that people settled Tibet much earlier than that.

Maybe the silliest line in any of these papers was in the abstract of the new one, where they say  (about adaptive introgression) “Therefore we identify a novel mechanism, beyond selection on new mutations or standing variation,  through which populations can adapt to local environments. “

People have been deliberately using admixture in domesticated animals to add favored local traits for thousands of years.  That ought to be long enough to get into the genetics curriculum, no matter what Ernst Mayr may have said.

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19 Responses to A novel mechanism for getting high

  1. Anonymous says:

    I suffer from altitude sickness and my identical twin does not

  2. Patrick Boyle says:

    I was perusing Wikipedia a week or so ago and I ran across an article on Tibet and the Chinese invasion. Apparently the vast majority of the Chinese public believes that they liberated the Tibetans. The Chinese claim that 95% of all Tibetans had formerly been slaves of one kind or another. They are proud that they have been able to free them.

    I don’t think this was any kind of Marxist interpretation – just some kind of altruism. That must also be the reason for them developing the Chengdu J-20.

    • harpend says:

      “Therefore we identify a novel mechanism, beyond selection on new mutations or standing variation, through which populations can adapt to local environments. “

      This is just painfully embarrassing, a consequence of the segregation of eebers and robbers in our biology departments. See our old post at http://westhunt.wordpress.com/?s=eebers .

      No matter, journalists will breathlessly proclaim the discovery of “a new mechanism of evolution”.

  3. dearieme says:

    @Stovner: it reads like a parody. Can you assure me that it isn’t?

  4. Jim says:

    I’ve read stuff on the internet regarding epigenetics that explicitly use the word “Lamarckism” and state that Lamarckism has now been vindicated.

  5. Alan says:

    If you read the paper, the mechanism they describe is selective enrichment of adaptive loci from high-altitude ancestors post admixture. It is actually a new mechanism, albeit nuanced, different than selection on standing variation or de novo mutations. Judging a paper based on its abstract is a poor idea. Harpend: criticizing a paper off of one line from the abstract spreads the very journalistic sensationalism you seem to dislike.

    • gcochran9 says:

      I read the whole paper.

      John Hawks and I wrote about adaptive introgression from archaic humans in 2006. Which has since been confirmed. 2006 < 2014.

      But we never claimed that we were the first to talk about this mechanism.

      People were talking about it in the late 1930s: (Anderson and Hubricht 1938; Anderson 1949; Heiser 1949) 1938 < 2014.

      Ernst Mayr (1963)argued that this didn't happen, or was insignificant, in mammals, but he was an idiot.

      Lewontin talked about it in 1966.

      Plenty of cases are known. For example, mice in Europe have a high frequency of a warfarin-resistance allele that introgressed from a fairly divergent Algerian mouse, one that is barely interfertile (F1 males sterile, some F1 females sterile)

      Surely everyone knows about the rapidly spreading introgressive genes in that California salamander.

      Xeric tolerance apparently spread from Utah cliffrose to bitterbrush (Stutz and Thomas 1964)

      It has been a common phenomenon in domesticated plants and animals for thousands of years.

      I talk about it fairly often – for example, mentioned that SLC24A5 is more common in highland Ethiopia than one would expect from the overall fraction of non-African ancestry there.

      So how could anyone call it a new mechanism? I could put this more strongly.

  6. Douglas Knight says:

    I’ve heard the claim that invasive species don’t become invasive immediately on being introduced to the new environment, but take several generations of adaptation and usually have a sharp jump in fitness. I’ve heard the further claim is that this is by introgression of local defenses.

    • gcochran9 says:

      Sometimes this is the case. Obviously it can only happen when there are closely related native species – if someone introduced the platypus to Tennessee, the species wouldn’t be able to pick up any useful local genes. Except by horizontal gene flow through a retrovirus or whatever, which is quite rare.

      People have talked about this for some time, too.

  7. Greying Wanderer says:

    “At least, they were the immediate source…”

    i’d imagine cold adapted critters would survive longer up mountains especially if they had other advantages. yeti introgression ftw.

  8. dave chamberlin says:

    Here’s a question related to this thread. I remember Bruce Lahn way back in 2006 stating that a gene had entered the human gene pool around 37,000 years ago from another source, presumably neanderthals, and had existed in that population for something like 800,000 years. Now being an utter ignoramus on the technicalities of making such a claim I am asking a few questions. How come this kind of analysis isn’t done more often? For example on these altitude adaptive alleles. I facetiously commented last time we talked about this advantageous mutation that maybe it came from the abominable snowman, but who knows when and where these mutations came from. Was the science Bruce Lahn used to make his claim dubious? I dunno, it seemed awfully cool that he could do it but since I haven’t heard or seen much of this kind of analysis since then I have to wonder. What people don’t seem to realize is that southeast Asia was probably populated with loads of archaic humans but thanks to bones rarely being preserved in hot or humid environments we have virtually no record of them. It would be so cool if we could find a hundred more genes that entered the existing human gene pool at X date but existed in another archaic population for X years. So much is lost, so little is known before written history, it seems such a shame.

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  10. The fourth doorman of the apocalypse says:

    I think the introgression of alcohol tolerance genes was the most important way of getting high.

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