Boiling Off

In principle you can imagine a  group experiencing selection for some trait by having members leave.   However, it takes special circumstances, unusual circumstances.  First, the people who defect have to be uncharacteristic: they  have to differ from the group in the trait, having higher (or lower) than average values of that trait.  The trait has to be  heritable, but that’s not so much of an obstacle.  Most traits are.

The next point is hard to arrange: in order to select strongly, as large as fraction as possible have to leave (and they should be be as different as possible), but at the same time,  the per-generation fraction defecting has to be smaller than the rate of population growth, else the group simply goes extinct before anything interesting has time to happen.  Since the long-run rate of population growth has been close to zero for most of human history, this mechanism usually doesn’t work.

There are exceptions.  The  Amish are the clearest case.  They have very high  rates of population growth, and have had for a long time, possible only in a really non-Malthusian society like the US. They also have had a high defection rate,  but that has decreased quite a bit over the last century.  In one Ohio Amish community, it seems to have dropped from 30% down to about 5%.   Over times, high rates of defections may have selected for lower values of the ‘bright lights, big city’ trait.  It’s possible that the Amish are genetically ‘plainer’ than they originally were. In fact, this almost has to be the case. It’s not clear how much of the decline in defection is explained by selection: the Amish may also have developed social techniques that make defection less likely, or it might be that the outside world  is less attractive than it used to be.  Or all three things may have happened.

I call selection involving differential defection “boiling off” -  the lighter molecules escape more easily than the heavy ones, and the soup gets thicker.

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36 Responses to Boiling Off

  1. Melykin says:

    Maybe this has happened with Gypsies. Maybe the smarter and more ambitious among them merged into the surrounding European population and what is left is a sort of residue. Maybe also with First Nations people in Canada. Maybe only a sort of dysfunctional alcoholic residue is left on the reserves and the rest split.

    I’ve heard it theorized that the same thing may have happened among the working classes in the UK. Vaste numbers of them left for the US, Canada, Australia, etc. I knew a lady who worked as a midwife in Scotland and came to Canada after WW II and worked as a nurse. She believed that the average intelligence was higher in Canada and that the more intelligent people were more likely to have left Scotland, which is quite a small poor place.

    I’m not sure if any of these examples are relevant.

    • Greying Wanderer says:

      “Maybe this has happened with Gypsies. Maybe the smarter and more ambitious among them merged into the surrounding European population and what is left is a sort of residue.”

      Or the least xenophobic merged leaving the most xenophobic behind?

    • bruce says:

      >Maybe only a sort of dysfunctional alcoholic residue is left on the reserves-

      My old boss was a proud Northwestern USA tribe Indian- potlachs, big canoes, those guys. His dad taught him the language, taught him some of the old skills, taught him to always be proud of his culture, pushed him to marry inside the faith, and told him if he ever went back on the rez to never darken his door again.

  2. Thursday says:

    Riffing off of Eric Kaufmann, could this now apply to religious people in general in Western societies? Those who could be secularized, have been secularized, and now all that are left are the high breeding patriarchalists. Even the most conservative mainstream churches (with the possible exception of the Mormons) don’t seem to have developed any better techniques for retention.

  3. The fourth doorman of the apocalypse says:

    Do the Viking count?

  4. Candide III says:

    Russian emigration around 1917 could be an interesting example. They were quite distinct from the peasant masses, and most of those who didn’t leave were soon disposed of.

  5. dearieme says:

    It cuts both ways. Think of the number of immigrants to the US who were looking for somewhere where competition was less severe than in mature societies where they couldn’t hack it, or who were fleeing the law, or creditors, or wives.

  6. dave chamberlin says:

    When a country becomes overpopulated, poor, corupt, and just a horible place with a rapidly decling future guess what happens. The people that can get out. At different times and places it is different groups or pretty close to random selection that determines who leaves and who stays. Today we are seeing a mass exodus from a whole slew of third and second world countries of their professional class. It is a nice phrase “boiling off” I think I’ll use it. Not much is being made of this boiling off of a nations professional class as of now but I will sadly wager that history will point to this event as a key trigger to a new economic word being invented. It will combine chaos, an economic super depression, and a mass hysteria of everyone out for themselves. As a kindly old intellectual explained to me, a man who lived in Poland through World War Two. “It takes three days with no food to turn a civilized man into a complete savage.”

  7. Greying Wanderer says:

    Isn’t that what happens here?

    http://en.wikipedia.org/wiki/Hajnal_line

    “West of this line, the average age of marriage for women was 23 or more,[3] men 26, spouses were relatively close in age,[4] a substantial number of women married for the first time in their thirties and forties, and 10% to 20% of adults never married”

    The non marrying part of the population is being boiled off and they are different from the rest of the population by having a below average marriagable quotient MQ – which if at least part of the selection was sexual selection would include fertility markers?

    Thinking about it if
    - marriage was entirely assortative on physical attractiveness
    - attractiveness was directly correlated with fertility
    - the fertility of a couple was based on the lowest value of the pair
    then i think that form of assortative mating would maximize fertility.

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  9. ironrailsironweights says:

    Another possible example would be the rural Midwest counties with declining populations. It could be that the people left behind are of a different sort than those who sought opportunities elsewhere.

    Peter

  10. The fourth doorman of the apocalypse says:

    In the spirit of seeking out the wisdom of the ages, could you comment on the genetics of this study?

    Study shows that women with big breasts are more intelligent

    Perhaps their mistake was that only men were the judges, but I have a wondrous vision of the future: Super intelligent women with KK cup sizes!

    • The fourth doorman of the apocalypse says:

      On second thoughts, perhaps they are measuring non-additive variance (environment).

    • RS-prime says:

      Wouldn’t shock me if it were true… consider the ‘general fitness factor’, or, assortive mating/ class.

    • Greying Wanderer says:

      If a population were in an environment that selected for higher average intelligence and that population also had an above-average level of sexual mate selection (as opposed to familial/clan based mate selection) then the two might correlate if you compared their descendents with the descendents of populations that didn’t have the same evolutionary pressures.

  11. JayMan says:

    That “study” is fake. Just try to track down the original paper…

    It’s too bad though one would imagine that the stereotype got started somehow…

    • The fourth doorman of the apocalypse says:

      Couldn’t track it down. A reference to the “study” first seems to pop up in 2003. None of them provide a link to the actual paper. I wonder if it was on April 1.

  12. Matt says:

    I wonder how much this affects variance as opposed to means… that is, are the genetically “plainest” amongst the modern day Amish “plainer” genetically than any individual ever was in the proto-Amish population, or do the Amish just have reduced variance in this trait?

    • RS-prime says:

      You should reach new heights of plainness in some individuals. Since we’re talking about 2-400 years, new/young mutations are a non-factor — unless there be some alleles of large plainness effect, as large as the effects of the proposed Ashkenazi IQ alleles.

      Presumably there aren’t any of those, but you are still assembling higher concentrations of already-existing plainness alleles than were ever present in any past individual.

      I don’t see much difference in principle from artificial breeding . . . and in that sphere, won’t there soon occur individuals more archetypal (or just faster, smaller, better at herding sheep, whatever) than any previous ones? — why naturally.

      Of course, if humans had spread to Mars in 200 AD and there were now 100 septillion people there, then the human beings with the most Amish or most Haredi personalities would be found over there, not here, by force of sheer probability — even if those cultures/communities never existed over there, and their existence is even unknown there. That’s just nature’s perversity.

    • RS-prime says:

      You should reach new heights of plainness in some individuals. Since we’re talking about 2-400 years, new/young mutations are a non-factor — unless there be some alleles of large plainness effect, as large as the effects of the proposed Ashkenazi IQ alleles.

      Presumably there aren’t any of those, but you are still assembling higher concentrations of already-existing plainness alleles than were ever present in any past individual.

      I don’t see much difference in principle from artificial breeding . . . and in that sphere, won’t there soon occur individuals more archetypal (or just faster, smaller, better at herding sheep, whatever) than any previous ones? — why naturally.

      Of course, if humans had spread to Mars in 200 AD and there were now 100 septillion people there, then the human beings with the most Amiish or most Haredi personalities would be found over there, not here, by force of sheer probability — even if those cultures/communities never existed over there, and their existence is even unknown there. That’s just nature’s perversity.

    • RS' says:

      You should reach new heights of plainness in some individuals. Since we’re talking about 2-400 years, new/young mutations are a non-factor — unless there be some alleles of large plainness effect, as large as the effects of the proposed Ashkenazi IQ alleles.

      Presumably there aren’t any of those, but you are still assembling higher concentrations of already-existing plainness alleles than were ever present in any past individual.

      I don’t see much difference in principle from artificial breeding . . . and in that sphere, won’t there soon occur individuals more archetypal (or just faster, smaller, better at herding sheep, whatever) than any previous ones? — why naturally.

      Of course, if humans had spread to Mars in 200 AD and there were now 100 septillion people there, then the human beings with the most Amish or most Haredi personalities would be found over there, not here, by force of sheer probability — even if those cultures/communities never existed over there, and their existence is even unknown there. That’s just nature’s perversity.

    • RS says:

      You should reach new heights of plainness in some individuals. Since we’re talking about 2-400 years, new/young mutations are a non-factor — unless there be some alleles of large plainness effect, as large as the effects of the proposed Ashkenazi IQ alleles.

      Presumably there aren’t any of those, but you are still assembling higher concentrations of already-existing plainness alleles than were ever present in any past individual.

      I don’t see much difference in principle from artificial breeding . . . and in that sphere, won’t there soon occur individuals more archetypal (or just faster, smaller, better at herding sheep, whatever) than any previous ones? — why naturally.

      Of course, if humans had spread to Mars in 200 AD and there were now 100 septillion people there, then the human beings with the most Amish or most Haredi personalities would be found over there, not here, by force of sheer probability — even if those cultures/communities never existed over there, and their existence is even unknown there. That’s just nature’s perversity.

  13. Peter Johnson says:

    There is some evidence for an increase in schizophrenia and related maladies in the western part of Ireland due to selective emigration during the 19th century. Those with a genetic disposition toward mental illness were not willing/able to emigrate and this increased the relative frequency in the remaining population.

  14. AG says:

    This might explain that people from Catholic countries have higher sex drive.

  15. Anonymous says:

    i was in egypt last week and what struck me was the difference between the nile delta arab/sudanese majority & desert dwelling bedouin nomad minority.

    the bedouins explicitly reject regular life, don’t have passports, don’t share birthdays, breed cattle for a living and are basicly part of wildlife.

  16. Anthony says:

    at the same time, the per-generation fraction defecting has to be smaller than the rate of population growth, else the group simply goes extinct before anything interesting has time to happen.

    Is this true in the general case? Don’t most human populations under malthusian conditions have more children than will survive to adulthood? If enough members of the group are leaving, that should improve the survival chances of the children of those left behind, so that the original population is maintained.

    • Bob Arctor says:

      Not if the “boiled off” population stays in the same general area and competes for the same resources, which until relatively recently was probably almost always the case.

  17. Don Strong says:

    Romney suggested a form of boiling off, NO? All of those illegal browns should boil off by self deportation.

  18. SOBL1 says:

    Havent the Amish been more successful with retaining their young because farmland prices dropped in the 80s and 90s which allowed families to help 2nd and 3rd sons stay in the Amish country? I would think the growing dysfunction on the surrounding society would help the Amish retain some 18 year olds.

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