Bill & My Excellent Hypothesis

In January I said:

In October I reviewed explanations for the clearly-maladaptive demographic transition, whereby societies consistently have fewer kids as they get rich. I leaned toward:

Lower … acceptance of childbearing and motherhood as measures of the status of women.

On a recent long drive, Bill Dickens and I developed an intriguing elaboration of this theory. The key idea: farming pressures strengthened a fem forager tendency to, when personally richer, invest more energy in pursuing status, relative to raising kids. So when all fems are rich, they all invest more in status, relative to kids, and fertility falls.

Ok, now for the details. When men vary in status and mating can be covert, high status men have two kinds of mates: a few “overt” mates, whose kids will inherit much of his status, and many “covert” mates, whose kids won’t inherit his status and who may have their own overt mates. While a top man will want as many covert mates as possible, he will be choosier about overt mates, wanting them to seem high status, to raise the status of his overt kids. Women will want to be overt mates of such top men, so that their sons can have a better chance to be top men, and then get many covert mates.

Given such status-varying men, women must choose how hard to try to become an overt mate of a high status man. A big part of this effort will be investing in status markers, such as abilities in music and art, good taste in clothes and food, travel experience, etc.  In addition to helping her attract a good overt mate, such status will also help a woman attract better covert mates, and protect and support her kids. Our theory doesn’t much care what exactly are these markers; the important thing is that markers take time and effort to achieve, in addition to raw ability, time that isn’t spent raising kids.

But raw abilities, i.e., an initial endowment of genes, parental status, property, etc., matters as well. There is no point in trying hard if you don’t think you have the raw abilities to make it work. So how much effort a woman invests in developing status markers should depend on her own private evaluation of her raw abilities. Energy not devoted to developing one’s status in the hope of attracting a top overt mate can be spent creating and raising kids via the best overt and covert mates one can find. Our theory doesn’t care what exactly are the indicators young women use to guess their raw abilities, as long as such indicators look stronger when she is richer, healthier, etc.,

Now if all a woman’s status marker efforts were realized by the age of sixteen, with no further hope of improving her markers, there’d be no point in waiting much longer to start having kids. But if a woman can continue to develop her markers for another decade or more, then she would face a difficult choice: give up now and start having kids with the best man her current markers can currently attract, or continue to develop herself in the hopes of attracting a better man later. The better her raw abilities, the more she might be tempted to wait. While a top man might be willing to gamble that a promising young woman will realize her apparent potential, basing his choice on the makers she has so far developed, he might prefer to play it safe and pick a somewhat older women who has more clearly realized her promise.  With age, status markers become clearer signals of raw ability.

We can model this as a one dimensional signaling game, if we think of raw ability, effort, and status marker level achieved all as one-dimensional parameters. A woman would privately see her raw ability, choose a matching effort level, and these would together determine her status marker level. Standard one-dimentional signaling models then make an important relevant prediction: signaling incentives distort actions most for the best agents, and not at all for the worst agents. Translated to our context, the prediction is that women of low raw ability put much less effort than high ability women into developing status markers. So if all women had enough food to feed their kids, high ability women would have fewer kids, who being higher status would produce more great-grand kids.

Now all of the above applies equally to forager, farmer, and industry era woman. But the low fertility of the demographic transition seems to be quite non-adaptive behavior evolutionarily, at least if current wealth levels continue for a while.  So to predict this anomaly, we need to posit some sort of adaptation error; something must be going wrong.  The error we posit is that women’s evolved machinery to manage this status effort problem failed to consider the possibility that societies could get much richer as a whole, and stay that way for a long time. That is, when estimating her personal raw abilities to achieve high status, and hence a top man, a woman may look at her own wealth, health, etc., but does not sufficiently consider the long-term average wealth, health, etc. in her society. If forager societies did not vary much along such lines, there would have been little reason to evolve status seeking behavior that depended on this context.

We thus conclude that as societies as a whole have gotten much richer, healthier, etc., unconscious female status-seeking machinery has been fooled into thinking it has a good chance at attracting a top overt mate, and the large reproduction gains that represents. After all, by ancient standards women today live in magnificent palaces on luxurious estates.  This mistaken judgement is apparently confirmed when women see the impressive status markers held by the men they can attract. So women have been fooled into investing greatly in status, far more than their real relative raw abilities can justify; they can’t all get a top overt mate.

Now the fact that foragers lived in bands of 30-50 overtly egalitarian folks limited the reproduction gains from being a top man, and hence the gains from being the overt mate of such a man. But farming introduced much denser living, explicit class hierarchies, and often explicit larger harems for very top men. This greatly increased the gains to women from being the overt mate of a top man. We posit that some free parameter in unconscious female status-seeking machinery, a parameter describing the magnitude of status gains, has evolved over the last ten thousand years or so.  That is, with farming women evolved to more eagerly seek status when of high raw ability.

In sum, Bill Dickens and I posit that farming fems learned that, compared with foragers, farm fems get larger reproductive gains from being an overt mate of a top man; her son might then also be a top man with many covert mates. Bill and I also posit that unconscious female status-seeking machinery never learned that when estimating their chance of achieving this end, they should attend not only to their own personal wealth, health, etc., but also to the long-term average levels of such things in their society.  Before the industrial revolution, societies just never varied enough in such things to make this attention pay off. Now when industry has suddenly made everyone rich and healthy, women unconsciously assume they all have a big chance at attracting a top man as an overt mate, if only they invest enough in accumulating status markers. So women in rich societies invest more in status markers, and wait longer before giving up and having kids with the best overt and covert men they can find. Hence the demographic transition: fertility falls as wealth rises.

What about men?  Much of this analysis also applies to men. Men also have raw abilities, must put in effort to convert abilities into status markers, and resources used this way reduce resources to support kids. Unconscious male status-seeking machinery may also fail to consider society’s long-term average health, wealth, etc. when estimating a man’s chance to gain high status and many covert mates. So men today may also devote excess effort to developing status markers. The main differences seem to be that 1) men tend less to directly raise kids, 2) men can father kids at older ages, and 3) men gain more reproduction from being high status.  So men should work even harder to gain status markers. But even so, raising overt kids will less distract men from pursuing high status, and a man’s delay in starting kids will less reduce his fertility.  Thus excess male status efforts probably do less to reduce overall fertility.

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  • http://un-thought.blogspot.com/ floccina

    whereby societies consistently have fewer kids as they get rich

    But is that even true. During the great depression the birth rate fell. Also I have read that urbanization even without greater wealth leads to lower birth rates. It could be that in an urban environment women see more men and thus are attracted to the same men and less likely to settle. This would explain singleness and insecurity about having many children even when married. Add to this that in an urban environment children are less of a productive asset.

  • http://ahappinessexperiment.wordpress.com/ Bock

    It’s highly questionable whether a woman improves her status as a mate by investing in much beyond the age of 21. She isn’t going to get much prettier or smarter beyond that age — and most men don’t seem to be attracted to a woman because of her career.

  • MichaelG

    So you’re assuming here that a woman has a mechanism for evaluating her own status independent of her group? That she doesn’t compare with people around her?

    That seems unlikely.

  • Doug S.
    • Cyan

      Dude, you’re harshing his buzz!

    • http://entitledtoanopinion.wordpress.com TGGP

      That’s not really a rebuttal. It says ev-psych theories more weight than should be warranted and people unduly consider certain things to be “iron clad certainties”. But Robin made plain this is a hypothesis he developed with an associate during a car ride. You might as well have just linked to this as your rebuttal, which would be even stronger since he hasn’t published this in a peer reviewed journal!

      Additionally, the complaint that evolution didn’t stop at the pleistocene explicitly does not apply to Robin’s hypothesis (which distinguishes farmers from hunter-gatherers). And the point that the evolution exploited outdated gene-environment relationships is made by pretty much all evolutionary psychologists, most especially those that focus too much on a single homogenous Evolutionary Adaptive Period as the font of all modern psychology!

  • lior

    What raw skills other than physical attractiveness raise a woman’s overt-mate market value? There may be a few, but none come close to looks. Therefore, it’s not wealthy females who decide to invest in status markers, only the self-determined attractive ones.

    I agree that more female wealth allows more women to invest in status markers. However, only the relatively attractive status-seekers will have a non-trivial effect on fertility.

    I believe female hypergamy explaining the drop in fertility is a simpler hypothesis.

    • nazgulnarsil

      men compete on resources, females compete on altruism.

  • http://timtyler.org/ Tim Tyler

    The last time this was discussed at least two other theories were mentioned:

    One was the idea that the humans had their brains hijacked by memes – that are adapted to channel resources towards their own reproduction – not that of their hosts.

    The other was the idea that developed countries encouraged more K-selected strategies – maybe acting as a superstimulus for K-selection.

    I figure that, next, differences in predictions need to be investigated.

    • Konvkistador

      This is exactly what I was thinking. If any interesting further discussion can be made we need to do some mental legwork and make predictions for these “theories” as well as perhaps think of what would constitute counterinidcations. It would be very pleasant if one or more where shot out of the way by real world evidence.

  • http://www.angryblog.org Brian Moore

    “The error we posit is that women’s evolved machinery to manage this status effort problem failed to consider the possibility that societies could get much richer as a whole, and stay that way for a long time. ”

    This sounds like a feature of a great deal of human issues. Such as, the reason we get fat is because our bodies are not designed to react to a world where we have constant access to high-calorie foods. And many others.

  • Nick Walker

    This article suggests women are going to elite schools to meet elite men:

    http://www.nytimes.com/2005/09/20/national/20women.html

    Key “female” assumption: a male graduate of Yale Law is more likely to marry a female graduate of Yale Law and not his secretary.

    The upshot is women need the same amount of schooling and training to interact with men as equals. A few years ago, high school and some college was enough, but today you need graduate school or more lengthening the time horizon.

    It’s possible extra levels of eduction are used by employers to screen applicants, and therefore aren’t necessary to actually execute the job, but the fact is several years of schooling are now the norm.

    I think men are putting in the time needed to gain a good job, then women put in the time needed to keep up with the men, and as a result women put off child-raising.

  • http://garethrees.org/ Gareth Rees

    I think it might be worth investigating the demographic literature more thoroughly before looking for evolutionary hypotheses.

    In particular, when you look at subgroups within a population, you can find quite large differences in fertility between subgroups of similar economic status (for example, Mormons in the USA, or Haredim in Israel). This suggests that cultural factors dominate biological factors.

    One of the important factors in the demographic transition that was missing from your list is the increase in the age at which women give birth to their first child. (Wikipedia: advancedmaternal age.) Even neglecting the other factors, it’s going to make a big difference to the number of children she has if a woman starts her family at 30 instead of 15.

    Of course if you’re looking for an explanation, then you’ll want an explanation of why age at first birth has increased. But clearly cultural factors are important here, for example the participation of women in further and higher education.

  • Unnamed

    This is one of the more plausible pieces of evolutionary speculation that I’ve heard in a while. Nice job, Robin and Bill.

    I’m surprised that you didn’t mention the sexy son hypothesis, which similarly posits that some females can maximize their reproductive success by trying to have a son who will get a lot of mates. The sexy son hypothesis claims that good genes make a son prolific while Bill & Robin claim that high status makes a son prolific, but they’re still both special cases of what we could call the prolific son hypothesis. Both hypotheses face some of the same questions, like when in human evolutionary history the top (sexy or status) men were prolific enough for this to be a viable strategy for women (you say farming times, I’m not sure what the sexy son promoters say).

  • http://daedalus2u.blogspot.com/ daedalus2u

    I have another explanation. It relates to the hygiene hypothesis.

    One of the first things that wealthy individuals and regions do is acquire abundant clean running water with which to bathe. Europe started to do this in the 19th century, following the discovery of the germ theory of disease. Soap as a manufactured good soon followed, and by the mid to late 20th century the normal state in the developed world was to have your normal commensal biofilm of ammonia oxidizing bacteria nearly stripped clean.

    Then in the early 1960′s, the development of synthetic anionic sulfonated detergents (which are specifically toxic to ammonia oxidizing bacteria) exacerbated the loss of NO/NOx species still further. In the 1980′s, the advent of conditioning shampoo allowed hair to be washed every day, so it was, depleting these commensal bacteria still further. Now antimicrobial everything is the final straw.

    http://books.google.com/books?id=a3mwmXzpsjkC&lpg=PP1&pg=PA103#v=onepage&q&f=false

    What low NO/NOx does is mimic a high stress state, a state where getting pregnant is a bad idea. NO inhibits the rate limiting step in testosterone synthesis, so low NO causes high testosterone (and feedback increases in hair growth, to expand the niche where these bacteria live). High testosterone causes hyperandrogenic infertility and polycystic ovarian syndrome. It also causes high libido in women, a good strategy under conditions of high stress. Women with high libidos are better prepared to deal with the likely cause of the high stress conditions; men fighting for receptive females.

    Low NO causes infertility because it takes NO to maintain an oocyte in a fertilizable state. When there is less NO, the fertilizable window is shorter. Make it short enough and pregnancy is really hard to achieve, a “feature” during times of very high stress where it is a bad idea to get pregnant.

    The regulation of fertility by stress is very important, and so there are multiple and redundant pathways for it to be regulated. Causing a woman to “feel” like it is not a good time to get pregnant is another way, then she will take active measures to make sure she doesn’t get pregnant. Change her “standards” so no guy is “good enough”.

    • http://daedalus2u.blogspot.com/ daedalus2u

      Another way of looking at the effect of stress is to think of it as changing the discount rate, the amount that future goods, services, and even life itself are devalued compared to goods and services today, or in other words immediate consumption vs delayed consumption.

      This doesn’t just apply to money, food and fungible things, this is how health is valued too. In an emergency, as when running from a bear, where to be caught is certain death, the discount rate is made infinite, that is any “cost” is worth it to stay alive while the bear is chasing you. Your physiology does this calculation for you, and actually turns off repair pathways to conserve ATP and direct more energy to running from the bear. If you escape, what ever damage there is can be repaired, if it can’t be repaired you are no worse off than if the bear caught you. If the bear catches you, then damage doesn’t matter.

      I think that the near death metabolic state is invoked by the stimulant drugs of abuse, solvent huffing, by autoerotic asphyxiation, by the runner’s high and by the mania of bipolar disorder. All of these are euphoric, euphoria is a complex state, a complex state must be pre-configured by physiology, these are just triggers.

      If the effect is to increase the discount rate to infinity, then deterrence cannot work, as the “war on drugs” has shown. Once you are in that near death metabolic state with an infinite discount rate, nothing that happens to you in a month, week, day, or even in the next few minutes matters. Deterrence cannot work in such a state.

      In the context of the value of children, since children only return “value” when they themselves reproduce, there must be a discount rate associated with supplying them with care. If the discount rate is infinity, then children are never a good investment. Because over evolutionary time childhood mortality was so high, the likelihood of raising an infant to weaning is not that great.

      The discount rate associated with reproduction necessarily incorporates risks associated with reproduction. A high stress time is a high risk time to get pregnant, at some discount rate is will be a better course of action to wait. Of course, in the “wild”, women didn’t always get to wait, or get to choose their mates. Particularly under high stress times.

  • Captain Oblivious

    …or maybe extreme wealth is just such a recent “innovation” that evolution hasn’t had much chance to weigh in yet… obviously, all other things being equal, this is maladaptive behavior – but millions of other species have developed maladaptive behavior and paid the ultimate price: extinction of their bloodline, if not their entire species. No reason this couldn’t happen to us, too…

    In fact, seeing as how intelligence (self-awareness) is such an unprecedented event in the history of evolution, there are probably all sorts of “maladaptive” behaviors which can/will arise when “intelligence” and “the selfish gene” pull in opposing directions.

  • http://hanson.gmu.edu Robin Hanson

    floccina, “consistently” doesn’t mean “always.” I’d like to see someone expand an “urbanization” theory into more evolutionary detail. Same goes for Tim’s meme and K-strategy theories. As I hope my post suggests, it takes a lot to work out such detail.
    Bock & lior, you have clearly never observed a very high status man seeking a wife.
    Michael, I didn’t say women don’t compare themselves to other nearby women.
    Doug, are you really suggesting no one should ever suggest an evolution-based theory of any human behavior?
    Gareth, I suggested an explanation for delayed fertility.
    daedalus2u, it seems fertility is reduced mainly due to lower desire for kids, not lower ability to have kids.

  • http://daedalus2u.blogspot.com/ daedalus2u

    Robin, those two are coupled but not completely. Reduced desire is readily apparent in the modern world, and artificial contraception makes the desire to not have children a reality. In the “wild”, a lack of desire may not have been effective. Even now, the conception rate during rape (presumably in rape, if there is no desire to have sex, there can be no desire to have children with the rapist) is remarkably high.

    For some women, their desire to have children fluctuates with their cycle. Why wouldn’t that desire also be coupled to their ability to raise an infant until it is weaned? In the “wild”, if an infant could not be sustained until it was self-sustaining, then it would die of starvation. Any interruption in the chain of continuous daily feeding and the chain breaks and the reproductive cycle needs to start over.

    Modern conditions are too new to change the evolved paradigms which are from deep evolutionary time.

  • Russell Wallace

    Interesting theory, but I don’t believe it. Too elaborate, too many variables would have to be just so, to produce anywhere near the observed effect.

    Here’s my alternative, simpler theory:

    In the ancestral environment, opportunities to raise your status were few and far between. So evolution essentially told us: any time you see an opportunity to raise your status, take it, put everything else aside for the moment if you have to, because it’s the one thing that won’t come again.

    In the modern environment, there is such a glut of opportunities to raise your status that you can spend the entirety of what should have been your reproductive life doing nothing else. Therefore, many do.

    I don’t think this is a complete explanation, but I think it’s at least partly true. In particular, it addresses the question of why both male and female plans to have children always tend nowadays to be “maybe after I finish high school/graduate from college/get my Ph.D./get my career on a solid footing/have enough money for a mortgage, in a decent area of course/oops, too late”.

  • Cyrus

    In cultures where the top man has many overt mates, the top man’s sons are more likely to become victims of fratricide. Joining a harem is not a clearly dominant female reproductive strategy.

  • http://daedalus2u.blogspot.com/ daedalus2u

    Russel, how does a woman increasing her status increase the number of surviving and breeding offspring she has? Over evolutionary time, the average number of surviving and breeding offspring the average woman had was 2. We know it was 2 because if it was greater than 2 the population would have reached levels we know did not happen. A woman with 3 surviving and breeding offspring would be 50% more successful than the average woman, a gigantic increase.

    A man increasing his status may increase the number of children he has by a lot because he has more females and so conceives more children. The number of surviving children a woman has depends more on how many survive childhood than on how many times she gets pregnant. The number depends more on her health, her access to food, her ability to protect her children from harm, and whether she has someone to care for her children if she dies in childbirth.

    It is not at all clear to me that increased status improves the survival of a woman’s children.

  • tom

    I’m interested in the overt/covert part. It’s surprising that 2 of our past 3 presidents had fathers who where rogues with both types of relationships.

    1. Bill. Dad: either the bad guy they tell us about, or the guy with a complete and successful overt family and a covert son who became the most powerful man on earth.

    http://isteve.blogspot.com/2008/10/in-search-of-bill-clinton-psychological.html

    2. Barack. Dad: a guy who had multiple families and at least two successful Western sons.

    3. George W. Dad: a man whose accomplishments and size, if you didn’t hear him speak, would have sounded like a member of an uber-class. That’s ignoring the fact that he himself was a President and had a powerful father.

    Nothing I know of about RMN’s father, RR’s father or JEC’s father. But JFK’s fits.

    Best qualification to be President: have an alpha dad who is also smart.

  • http://allegedwisdom.blogspot.com Alleged Wisdom

    This theory does not explain why women have fewer children than they can afford after they become the overt mate of a high-status man. If it was all about delaying reproduction to attract such men, then we should observe that women have lots of children after they succeed in attracting such a man.

    I think that the simplest explanation is that we never evolved a proactive desire to have children because it was not necessary. Remember that we are adaptation executors, not fitness maximizers The sex drive, and a strong instinct to protect children once they arrived, was sufficient. But then we invented birth control.

  • http://entitledtoanopinion.wordpress.com TGGP

    Deterrence can work, even in the war on drugs. If you don’t believe me, ask Mark Kleiman. The problem is that the war on drugs generates a host of problems itself which just aren’t worth taking on (though since I don’t have a paternalist bone in my body, you’d expect my calculations to come out that way).

    The question is not just how many breeding offspring, but how many offspring those breeding offspring have.

    Alleged Wisdom makes a good point, though by the time women settle down they have often passed their peak fertility years.

    • http://daedalus2u.blogspot.com/ daedalus2u

      TGGP, when a self-injected drug user willingly uses needles they know are likely infected with HIV (because an HIV positive individual just used it to inject drugs), what punishment are you going to threaten that self-injected drug users with that will “deter” their drug use?

      The question isn’t whether you or any other non-drug abuser thinks that drug abusers “should be” deterred, the question is whether self-injected drug abuses actually feel deterred. Since the lifestyle they are already living is worse than the worst punishment allowed under the US Constitution, how can you deter them with punishment?

      • http://entitledtoanopinion.wordpress.com TGGP

        I once heard Drew Pinsky say that you were more likely to get infected from swimming in a pool containing one drop of hepatitis infected blood than injecting yourself with a full needle of AIDS-infected blood. And many IV drug users don’t know that they are using AIDS-infected needles.

        Possibly the biggest lesson Kleiman tries to impart is that increasing swiftness & certainty works much better than increasing severity. Hawaii’s “H.O.P.E” program had astonishing success with meth addicts just by threatening them with a day in jail if they failed to call in to check if they were being drug-tested that day, or failed their drug test. Doctors who have gotten themselves addicted to narcotics had earlier designed a similar treatment program based on close monitoring of whether the addict was clean and prompt responses. Mao Tse-Tung angled more for the severity end of the spectrum, but he was also successful in stamping out opiod usage. Singapore has the death penalty for drug dealers and I believe it has been more successful than our drug policies.

        I highly doubt if I aimed a gun at the head of a drug abuser and told them I would pull the trigger if they didn’t put down the needle, they would respond by noting their life was as bad as death anyway and proceed to shoot up. The death penalty has been expressly permitted from the beginning of the Constitution, and even if you object that it doesn’t apply to drug-users, just note how eager drug users in the H.O.P.E program are to avoid even a day in jail.

  • Robert Koslover

    Historically, and continuing in poor populations today, children are a form of weatlh. Having children improves your odds that someone will be around to take care of you when you get old. Hence the statement, “Bless you sir, may you have many children!” But nowadays, and in our more developed societies, children have instead become, in many cases, a huge expense. I think that children=wealth vs children=expense arguments go far to explain the number of children produced. That, and birth control. (Note: I realize that this actually be fully consistent with Robin’s essay, but I must confess to not fully understanding it.)

    • Robert Koslover

      Oops. “actually be fully consistent” should read “actually may be fully consistent” …(Hmmm. can we get a preview feature installed on this blog? Thanks.)

  • http://kazart.blogspot.com mwengler

    What about the more standard explanations, that industrialization removes the need for kids to help you, social security removes the need to have kids around when you are old, birth control, abortion, and modern mores make it trivial to have sex without kids, and the complexity of modern society has extended the parental responsibility for kids from ~12 years to ~30 years? Why build castles in the air when there are plenty on the ground?

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