Let’s Get Small

I said earlier than it seemed likely that archaic hominid living in special environments, for a long time (sometimes more than a million years) inevitably developed high-quality adaptations to those environments, and since such alleles are easily transmitted, modern humans were likely to pick them up. The recent discovery of a Denisovan altitude adaptation in Tibetans fits this model.

I also said that there was a specific suite of changes favored in dense tropical jungles (Pygmification) and you might expect to see adaptive archaic alleles there too. Mike Hammer and others have an abstract out in ASHG 2014 that supports this notion: there was already evidence for introgression from a very divergent hominid population in Pygmies and Bushmen, and they found some genomic regions that A.  look archaic and B. seem to have been favored by positive selection.

There is a good chance that we will find archaic variants involved in Negritos (probably Denisovan in origin),  Ethiopian altitude adaptations,  and Bushmen ( steatopygia?).  Could also occur with less-visible traits such as resistance to regional infectious diseases outside of Africa (such as scrub typhus in the tsutsugamushi triangle). 

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This entry was posted in Altitude adaptations, Bushmen, Denisovans, Mangani, Pygmies. Bookmark the permalink.

31 Responses to Let’s Get Small

  1. Cloudswrest says:

    “No Officer, I’m tall, I’m tall.”

  2. Ainu Mosir says:

    The Austronesian natives from Taiwan still tell a legend of “small people” that lived in the mountains, probably a Austroloid/Negrito group who got exterminated.

  3. dave chamberlin says:

    Unfortunately (for the sake of interested folks looking for these introgressed archaic genes) it seems very likely when anatomically modern man got his tool making shit completely together he didn’t waste much time in fraternizing with the locally grown archaics. Now this is a very wide sweeping comment that invites correction by our fearless leader so let me box it in further. When we got to Denisovanland we didn’t fuck around., very much., at all. When we anatomically modern humans got to moving out of the middle east after our very long incubation (sorry, no great leap forward) we kicked country butt and didn’t take names. At least that is the picture we now have from our modern DNA except for one glaring exception, there is a sizable Denisovan signature in the area around Australia.

    My guess is there are a lot more introgressed archaic genes to be found in Africa and disappointingly few outside of it.

    • minoritymagnet says:

      Why should there be a difference between Africans and non-Africans in this? The “modern” humans in Africa have no increased likelihood than non-Africans to aquire Archaic alleles (according to your logic). The Archaic alleles then must have been acquired before full modernity and before the out-of-africa migration. This means all humans should share pre-modern Archaic introgression. Alleles not present in non-Africans as against Africans would be attributable to different selective pressures or to founder effects.

      • dave chamberlin says:

        You ask a serious question, “why should there be a difference between Africans and non-Africans in their quantity of Archaic alleles.?’

        Because there was a bottleneck, a founder population, of people that left Africa to populate the rest of the world and this group carried with them a small percentage of the alleles remaining in the human population of Africa. This is widely believed because it is based on the evidence left in modern populations.

        • gcochran9 says:

          Not a small percentage. More like 80%.

          • dave chamberlin says:

            my bad. Apparently I need to be educated on some basics of allele distribution through populations. I would never guess that a small population could hold 80% of allele population in the total human population back in time when humans were expanding out of Africa.

      • Greying Wanderer says:

        I think the idea is that archaic hominids would likely survive longest and mixed most with AMH in regions where the archaics had specific adaptions that were particularly positive in that particular region e.g. the high altitude genes in Tibet.

        So you might expect to find the most archaic introgression in the most extreme environments e.g. tropics, very hot, very cold, very high etc.

    • Matt says:

      Archaic humans outside of African would have had less opportunity to get introgression from para-modern groups.

      So psychologically, I guess that might mean have been less competitive and modern-like.
      On the other hand, they’d have had more of a physical adaptation specialties (although Africa still has some climatic diversity and we don’t know moderns would have had time to adapt to most of it well without recent admixture, cf. jungles).

      Archaics out of Africa would be more psychologically and physically archaic, yet have more of a climatic advantage.

      Introgressions in gross physionomy as relates to climate might be of greater selective effect outside Africa, even if archaic genomes survive less well overall.

  4. Greying Wanderer says:

    a couple of small thoughts so almost on topic

    Do modern Swedes show signs of positive recent selection for malaria resistance? I’d guess no.

    Would the distant ancestors of modern Swedes have been strongly selected for malaria resistance at some point in their past before they got so far north? I’d guess yes.

    Is there potentially a consistent pattern within dna that what would act as a signal of strong positive selection on genes in the past which later stopped and/or went into reverse.

    #

    3 or 4 ifs

    If the average level of testosterone in a population inversely correlates to average levels of cooperation

    and if a human population either moves into a niche requiring more group cooperation or simply the average group expands beyond the size where there is only one dominant male at a time

    then you might think lower average levels of testosterone might be selected for over time when those conditions applied.

    If so and if eventual skull shape is related to testosterone in the womb couldn’t that imply that changes to skull shape could be a signal of changes in average testosterone levels?

  5. Steve Sailer says:

    Where is steatopygia big? Among Bushmen and Andaman Islanders, right? What’s the relationship (if any)?

    • Greying Wanderer says:

      food storage – famine insurance?

      • Kate says:

        the reason why crash diets don’t work is because after famine/crash diet, fat cells increase their ability to store fat – repeat famine insurance.

        btw i found some fascinating refs on sugar but didn’t want to clog up the blog. in a nutshell, oriental flea, rodents addicted to sugar, infected tartars defeated at kaffa, genoese fled back to sicily, plague spread up from med. so tartars might have drifted on into Poland if they hadn’t been stopped at kaffa. sugar depletes immune syst of people newly consuming sugar, Y.pestis attacks immune syst. plus there’s a natural cycle of disease, which may or may not explain why it didn’t get east from germany.

    • Sean says:

      Why is steatopygia in females, eh? There are other things about Bushmen females’ nether regions, got a lot of attention in their cave art . The males have their own peculiarities . Pygmy women don’t have big steatopygia, but the men have an advantage in life, they could replicate Forrest Tuckers ‘no hands’ putting feat. The bushmen can only support one wife.

      The trend in fighter planes and tanks is to get smaller as they get more sophisticated.

      • gcochran9 says:

        “the trend in fighter planes and tanks is to get smaller as they get more sophisticated.”

        Nope. You’re starting to remind me of someone. Try not to.

        • Sean says:

          Boyd’s Energy-Maneuverability would be useful for jumping out the way of projectile weapons. And being smaller means you are a smaller target. If you look at the older human types especially in Africa the amazing thing is how tall they were, and for comparison to us with modern height boosting lack of infection and environment you could add several inches to that. Humans have got a lot smaller in the last 25,000 years. So I think one possibility is that hulkling less agile males would be selected against with the advent of projectile weapons. But that is just a little pet theory of mine .

          I dare say you are right about introgression. However I don’t go along with an environment being the reason people get small in the way I understand you to be saying. Pygmies live in the thick tropical rain forest, where a man can have more than one wife. Bushmen don’t, Saami don’t either, and neither did ice age Euro HG; there was quite a reduction in size of Europeans during the Magdalenian. Which suggests a variety of reasons for getting smaller. Which may explain why Pygmies look a lot different to Bushmen, and why neither look like black Africans in characteristics apart from height. Do these three population really live in such different environments that they ought to look more different that many good species do?

          “The recent discovery of a Denisovan altitude adaptation in Tibetans fits this model.”

          Yes you’ve been right about the introgression. Nonetheless, there is also recent evidence that the altitude at which Tibetans live is correlated with mtDNA mutations, and the elevation -mutation adaption was incredibly fast, within the the last few hundred years. Lower mitochondrial DNA content relates to high-altitude adaptation in Tibetans Doesn’t disprove or take away from the intogression. But mtDNA may be able to evolve faster than, and even drive, nuclear DNA evolution, of growth to adapt to local conditions (food, climate) as found in mtDNA adaptations of fruit flies. And there are is also evidence of diet altering mtDNA, one mutation inevitably becoming dominant . Implications in humans may be that the Euro HG who altered their diet would look like a separate population if you looked at mtDNA. The same population living on meat, then grain, then and milk may have adapted with mtDNA each time. (which may be a little pet theory of mine too, I don’t know if anyone else has suggested it).

  6. Sandgroper says:

    ‘Where is steatopygia big?’ In the arse. I thought you knew, Steve.

    It also occurs in modern Australian white women, commonly associated with the dietary consumption of a food group known as Tim Tams.

    Tim Tams – fattening Australian arses since 1964.

    • MEH 0910 says:

      I know you’re being funny (the same joke occurred to me when I read Steve’s comment), but steatopygia doesn’t look like the typical female fat ass. It looks more like the human female’s version of a camel’s hump.

  7. Greying Wanderer says:

    off-topic

    http://www.sciencedump.com/content/lost-egyptian-city-revealed-after-1200-years-under-sea

    Pics from the city of Heraklion under the sea off Alexandria. Given the rise in sea level since the LGM there might be quite a few of these under the sea so I was wondering were some ancient tombs built with the stones so close together they’d be water tight?

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