DARC matters

DARC (Duffy antigen receptor for chemokines) is a receptor expressed on red cells, key in the infection of those cells by vivax malaria. A version of the gene that eliminates expression of this receptor on red cells (and prevents vivax infection) has reached very high frequency (up to 99%) in sub-Saharan Africa. A new article in PLOS Genetics concludes that this was driven by some kind of strong selection, but a long time ago ( ~40,000 years). They estimate that the Duffy-negative mutation conferred a selective advantage of about 4.3%, leading to effective fixation in about 8,000 years. Not everywhere in Africa – didn’t happen in the Bushmen, Naturally they suspect that the selection was driven by vivax malaria , but they’re a bit mystified because today vivax is usually mild ( at last when compared with falciparum malaria). Vivax is often found in places where it can’t be transmitted year-round (because of winter) : it waits in the liver [hypnozooites] and reappears later, sometimes much later. I’ve heard of cases where it reemerged as much as 40 years later. Which means that it can’t afford to be too severe – it has to let the host survive.

However, in the tropics, it could get away with being more virulent, and perhaps it did, in the past.

An advantage of 4.3% is a lot, as selective advantages go, easily enough to drive a gene frequency from a tenth of a percent to 99% in a few thousand years. In much the same way, a behavioral tendency (heritable of course) that led men to have sexual intercourse with women other than their primary mate, when practical, could become very common even if it only resulted in a few percent extra surviving children per generation, say 2.2 instead of 2.1 . Compound interest. A behavior wouldn’t have to yield 100 extra children in order to become common (although producing an extra 100 would certainly have that effect!). In the same way, a heritable behavioral tendency that reduced the average number of offspring by a few percent would also become rare over a few thousand years.

What fraction of the practitioners in various human sciences understand this wee bit of population/quantitative genetics? Very few, I think.

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44 Responses to DARC matters

  1. Sean Fielding says:

    Women are well prepared in subcortical centers to ‘get’ the selective advantage conferred by these non-provisioning genes, even while in complete denial about it at the cortical level.

    But wise nature has protected even (well, especially) very intelligent men from despair by giving them egos and pride in their civilized achievements, while hiding the real nature of women from them.

    Bad boys.

  2. Paul Conroy says:

    It’s why Cultural Marxism/Feminism = Neo-Shakers

    After this era of relative insanity, if we in the West are not overrun by Muzzies first, society will get more conservative, as conservatives are having the kids!

    • The Monster from Polaris says:

      It isn’t so much a matter of conservatives vs. liberals as of certain religious sects vs. secular people. Google ‘TFR laestadians’, and read especially http://blogs.discovermagazine.com/gnxp/2010/10/the-wheel-of-history-turns-to-the-gods/#.WNg42Z4lGUk.
      I don’t have time to read it right now, but it contains stuff like this:
      ” In Finland there is a branch of the sectarian Laestadian Lutherans. Their fertility is awesome. In the 1980s while the TFR of the majority Finnish Lutherans was 1.5, that of the Laestadians was 5.5.”
      Think about it. 5.5! As selective advantages go, this is enormous.

      • Maciano says:

        Yes, Eric Kaufmann did a good job describing these endogamous religious growth sects.

        I think the process is very clear in Turkey. First the secular Turks got outbred by the religious conservatives; now the Kurds are outbreeding the Turks in general, especially in the southwest. The country’s character seems to slide back to its older illiberal self.

        • albatross says:

          We’re an insanely wealthy society. The common trend is for wealthier societies to have fewer kids, probably because kids cost money in modern society (for braces, private schools, clothes, car, college, etc.), as opposed to bringing money in in earlier societies (going off to work in the dark satanic mills or spending their days in the field staring at the south end of a northbound mule). But people who want a big family can use that incredible wealth to have one–put the kids 2-3 to a bedroom, make it clear to the kids they’re going to public school and the local community college, etc. Most families I know have between 1-3 kids, but I know a fair number with 4, 5, 6, or more kids. The thing is, this can be done on a reasonable middle-class income, if you’re willing to accept a lower standard of living in terms of things like driving an old car, living in a somewhat more run down house, etc.

          The biggest determiner of fitness in the modern world is unwillingness to use birth control, or the desire for a large family. Neither of these things were very important in determining the fitness of a peasant farmer family in Ireland in 1600–nobody had decent birth control, so the size of your family was determined largely by whether you liked sex and how many of the kids made it to adulthood. But now, if there is a heritable element to the desire to have children or the unwillingness to use birth control, it’s being massively selected for.

          • Dave chamberlin says:

            I will troop out my poem again.

            The meek were supposed to inherit the earth
            But they aren’t the ones who most frequently birth
            It’s those without will
            who can’t swallow a pill
            Whose love of their children is their source of self worth.

            Meekness did make agriculturalists more fit for avery long time. A thousand years ago scandinavians were some of the most violent people on earth. Now they are some of the most peaceful law abiding people on earth. I would conjecture Jesus was right about people in his time period, the meek did inherit the earth. But now things have radically changed thanks in large part to the pill. Dumbshits are breeding at a much higher rate because planned parenthood isn’t a concept they can wrap their silly heads around. All we can say or do is wish genetic engineering of higher intelligence hurries up and gets here to save us from idiocracy.

            • ziel says:

              ” I would conjecture Jesus was right about people in his time period, the meek did inherit the earth.”
              Jesus’ stories were all about incongruities – describing a world that didn’t actually exist – fathers celebrating their wayward sons, holy men washing sinners’ feet, landlords commending their crooked caretakers. In early 1st century Roman Palestine, I don’t think anyone thought that the meek inherited the earth.

          • Temples and Ashes says:

            ” Most families I know have between 1-3 kids, but I know a fair number with 4, 5, 6, or more kids. The thing is, this can be done on a reasonable middle-class income, if you’re willing to accept a lower standard of living in terms of things like driving an old car, living in a somewhat more run down house, etc.”

            From personal experience, I can confirm that having a big family does not require much of a trade down in standard of living, especially for someone of above average intelligence. It just requires being practical and careful with your finances, something people should be doing anyway:

            1) Live somewhere with good affordable family formation characteristics (low cost of housing and good public schools), so not in urban coastal areas;

            2) Don’t waste your money on trivialities (such as eating out at restaurants a lot, paying for cable TV, yearly smart phone upgrades, etc.);

            3) Don’t buy new cars. You can find a good, reliable low mileage, late model used car that will last a long time and cost significantly less than a new one.

            4) (This is where intelligence comes into play.) Pick a practical profession with decent pay. There’s lots of options in many different fields, you’ve just got to look.

            And for people who worry about the extra work of having more kids, what I’ve noticed (both for me and friends) is that by far the biggest impact to one’s lifestyle comes after the first kid. Each additional kid adds a marginally lower amount of extra work/lifestyle change. Having one is a big change, the second is not nearly as big of a change, and for the third and subsequent children, the additional work and change in lifestyle is really quite small.

            And having kids is such a joy! By far the best and most rewarding parts of life, at least for me.

          • Salmed says:

            probably because kids cost money in modern society (for braces, private schools, clothes, car, college, etc.), as opposed to bringing money in in earlier societies (going off to work in the dark satanic mills or spending their days in the field staring at the south end of a northbound mule).

            You nailed it. Children take too long to become remotely productive. As society advances TFR (accounting for lifespan) drops and becomes irreversible to any large amount.

            Religion alone doesn’t help. Neither does chauvinism. The majority of Muslim countries outside of Tropical Africa (by far the most backwards area on Earth with the lowest lifespans) only have about two children per parent. The Far East is at best around the same level, if not worse. It’s not a racial issue considering how low Jamaica, Mexico, and South America’s TFRs are.

            Our world is designed around an apparent economic model that assumes you can have an industrial Earth that won’t keep on becoming more industrial remotely soon, AND a world TFR that largely has about two, maybe three at best, kids per parent.

            • Salmed says:

              Our world is designed around an apparent economic model that assumes you can have an industrial Earth that won’t keep on becoming more industrial remotely soon, AND a world TFR that largely has about two, maybe three at best, kids per parent.

              Let me fix that. I meant to say this:

              Our world is designed around an apparent economic model that assumes you can have an industrial Earth that won’t stop becoming more industrial remotely soon, AND a world TFR has three kids as a minimum instead of a higher reach

      • another fred says:

        Sometimes I get the feeling that a realization of these trends is part of what drives the policy of expanded immigration. Ted Kennedy (spit) and his ilk didn’t want those nasty old conservative religious people taking over the country by outbreeding the Left, hence the Immigration Reform Act of 1965.

    • Greying Wanderer says:

      didn’t conservatives have most of the kids in the 1960s?

      it seems the schools and TV might be more critical

  3. JayMan says:

    1%. I’m feeling generous.

  4. pyrrhus says:

    I have taught many grade school kids who would understand this basic process in very short order, some within seconds….The fact that there are scientists who don’t understand it is frightening.

  5. MawBTS says:

    Why didn’t the Bushmen grab this gene? No inward gene flow, or selective pressure against?

    Ed Yong thinks they didn’t need resistance, because their low population density reduced incidence of disease. That doesn’t sound right to me. Malaria is spread by mosquitoes, not person to person contact!

    Schuster’s team also analysed the genes of three other Bushmen – G/aq’o, D#kgao and !Aıˆ

    I always liked how Bushman names are completely indistinguishable from a cat walking across a keyboard.

    • Sandgroper says:

      Malaria is passed from one person who is a carrier to another uninfected person – the mosquito is just the vector. Most mosquito species have a very limited flight range. So Ed Yong’s logic still applies.

      In the past, efforts to control malaria were directed at the mosquitoes. Wrong idea. New research is now being conducted by Australian scientists in Papua New Guinea aimed at detecting people who are asymptomatic carriers – if all those people can be detected and treated, malaria can be eliminated.

    • Temples and Ashes says:

      There’s no malaria in the Kalahari, or in the other areas where most bushmen live in Namibia, Botswana, and South Africa. There’s a reason people of European ancestry settled in those same general areas too and not further north–there’s no malaria.

      I live in southern Africa, have been to the Kalahari plenty of times. No one worries about malaria there, no one takes malaria meds or uses nets, and no one gets infected.

      See this map of malaria areas: https://www.iamat.org/risks/malaria

      And even that map is slightly deceptive, as many of areas in red are not year-round high risk areas. See, for example, this more detailed map of Namibia: http://www.gamelodges.com/resources/maps/map_namibia_malaria.htm

  6. Many well-educated moderns are more worried about increasing the amount of wilderness, eliminating meat from our diets, and reducing the carbon footprint of North America. Because those things will save us.

    It all depends on where you put your focus.

  7. Douglas Knight says:

    Vivax jumped to humans 40kya. When a parasite crosses hosts, it usually starts virulent, harming the host by accident of its adaptations to the prior host, rather than as a result of aggressive propagation. So they usually evolve to be less virulent.

    What do you think of the theory that this is the difference between falciparum and vivax, that falciparum is only 5kyo and is still evolving away from virulence? If so, vivax at the time of the evolution of Duffy would have been like falciparum. In fact, with smaller population sizes 40kya, vivax would have evolved slower than falciparum.

    Or is a millennium a long time for Plasomodium, and its evolution would have reached equilibrium long before? And the equilibrium would be determined, as you suggest in the post, by the means of transmission, such as the ability of vivax to hibernate. But if falciparum is such a good fit to its niche, at least in recent times of high population density, why didn’t vivax speciate and the tropical version invade the niche?

    • gcochran9 says:

      “What do you think of the theory that this is the difference between falciparum and vivax, that falciparum is only 5kyo and is still evolving away from virulence?”

      I think it’s wrong. Severity goes up with the fraction of erythrocytes infected, but so does transmission. If transmission relied on the infected human walking around, selection would push towards low virulence, but instead it depends on the vector, the mosquito.

      Vivax spread depends on hypnozooites, falciparum does not.

      If selection really did favor a mild falciparum – well, it has short generations. You’d see change in 10 years, just as you do with artemisin resistance.

      Not original thoughts of mine – Paul Ewald’s thoughts. they make sense to me.

      • albatross says:

        Have you read Martin Nowack’s Evolutionary Dynamics book? He talks about some of the ways you can get evolution for more/less virulence. One example I remember was that if you have multiple different strains of virus infecting the same host at the same time, there is a big selection for virulence there, because the strain that reproduces the fastest (trashing the place, but having the most offspring) wins the race against the friendlier viruses. It’s like a pocket description of how individual selection can trump group selection–all the virus strains would do better to keep their host alive longer, but among the virus strains, the most virulent is the most successful.

  8. alcibiades96 says:

    go on joe rogan’s podcast!

  9. albatross says:

    I think compound interest type changes are unintuitive to most people, even ones who know about them in principle–probably not a whole lot of our species’ evolutionary environment was set up to select for an intuition about such things. The best solution I know for this is to explicitly think about the numbers and think about the equations involved.

    This is a common phenomenon. Storytelling is a powerful way to convey ideas and information, which engages our intuition, and we’re all used to seeing stories that seem to make sense of the world. And yet, it’s shockingly common that when you stop thinking in terms of the story and try to put some numbers on what’s being talked about, look for data, and maybe write down an equation or two, the picture that emerges is 180 degrees flipped from the nice plausible verbal story. I think most of our ruling class, and nearly all of our media class, is selected from verbally smart people who are bad at thinking quantitatively. They lie to us at the same time they lie to themselves, and they never even realize they’re doing it.

  10. Greying Wanderer says:

    o/t but kinds health epidemic related

    if astronauts lose bone density in zero g that implies the body only creates as much bone as it needs for the load stress it’s under and will even take existing bone away (as unnecessary weight?) if it’s not needed.

    if correct, wouldn’t this apply to osteoporosis: low load stress -> thin bone?

    all else equal, the proof might be sitting jobs vs standing jobs?

    and the cure some method of artificially increasing the load on the hips like kneeling chairs (?) or weighted shoulders (?) or astronaut exercises (?)

    • Sandgroper says:

      Or getting up and walking around every 30 minutes, which is what is recommended.

      “low load stress -> thin bone?” – Obviously. You have just discovered what the rest of the world has known for a long time.

      It has been known for decades that osteoporosis in old age can be prevented by doing regular load-bearing exercise such as walking or running or, preferably, weight training.

      • Greying Wanderer says:

        yeah – i googled after i wrote it – doh.

        i was watching The Expanse again and thinking, if we know astronauts lose bone then why do all the doctors prescribe calcium supplements?

        (like they did to one of my relatives recently)

        #

        “You have just discovered what the rest of the world has known for a long time.”

        Not true – which is why it’s not entirely off-topic for this blog. Yes, some of the world has known it for many years but it hasn’t been applied generally. Calcium supplements have been applied instead – and from my reading they’re made out of rocks and don’t do anything except maybe give you heart attacks.

        Anyway – i told my relative to throw away the calcium supplements and get a weight vest instead.

        • Sandgroper says:

          “The rest of the world” might have been somewhat hyperbolic of me, but you needed to be on a different planet to miss all the stuff in the mainstream media about people using ‘standing desks’ to work at, in response to the years-old news that % time spent sitting is inversely correlated with age at death. Just sitting around will kill you, literally.

          The latest thing I saw was “Will exercising for an hour every day compensate for the adverse effects from sitting down for the rest of the day?” The answer is “No”, apparently. You need to get up and walk around, frequently.

          Seriously, the knowledge that you need to exercise to maintain bone density is several decades old. Swallowing rocks won’t do it.

          Some other news that you might have missed is that physical exercise helps to maintain fluid intelligence past the age of 25, probably by increasing the flow of oxygen to the brain. Doing crossword puzzles when you get old doesn’t do shit, except pass the time while you’re waiting to die.

          It’s yet another reminder that it is scientists who do medical science research, not doctors.

          • Greying Wanderer says:

            “but you needed to be on a different planet to miss all the stuff in the mainstream media”

            I’ll be sure to mention that to the Docs who suggested calcium supplements and didn’t mention exercise.

  11. Rich Rostrom says:

    “a behavioral tendency (heritable of course) that led men to have sexual intercourse with women other than their primary mate, when practical, could become very common …”

    There is evidence that aggressive male sexual promiscuity can be an evolutionary advantage (more offspring conceived)- but so can male monogamy and parental devotion (more sex with a quality female, more offspring surviving to adulthood). Each pattern is most advantageous when the other pattern is dominant.

    • j says:

      Do you suggest that there is a cycle in human affairs of times when monogamy is more advantageous followed by a period when promiscuity is more effective? In what point of the cycle are we now?

      • Hulegu Khan says:

        Turn on the video broadcast device known as a “TV” and I think you’ll figure out swiftly where we are in the cycle.

  12. Greying Wanderer says:

    should astronauts sunbathe?

    (i mean have some kind of pod made of a material that only lets in a small amount of UV and sunbathe in it?)

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