Society seen through genes

By Razib Khan | July 15, 2012 2:39 pm

Over the past few months more and more articles like this one in the The New York Times are coming out, Two Classes, Divided by ‘I Do’:

Jessica Schairer has so much in common with her boss, Chris Faulkner, that a visitor to the day care center they run might get them confused.

They are both friendly white women from modest Midwestern backgrounds who left for college with conventional hopes of marriage, motherhood and career. They both have children in elementary school. They pass their days in similar ways: juggling toddlers, coaching teachers and swapping small secrets that mark them as friends. They even got tattoos together. Though Ms. Faulkner, as the boss, earns more money, the difference is a gap, not a chasm.

But a friendship that evokes parity by day becomes a study of inequality at night and a testament to the way family structure deepens class divides. Ms. Faulkner is married and living on two paychecks, while Ms. Schairer is raising her children by herself. That gives the Faulkner family a profound advantage in income and nurturing time, and makes their children statistically more likely to finish college, find good jobs and form stable marriages.

The story is set up to illustrate the importance of contingency. Two women with very similar backgrounds, and presumably aptitudes, make two very different decisions early on in their lives, and that sets their life path via the constraints or options that that choice enables. We’ve come a long way from the early 1990s when there was a debate, at least at the higher cultural strata, about the necessary value of marriage. But this part jumped out at me:

They stayed with Ms. Schairer’s brother, [the single mother -Razib] visited SeaWorld and Gatorland, and brought back happy memories. But the trip soon began to seem long ago, more a break from their life than an embodiment of it.

I have a dream that in the near future with widespread genotyping that social scientists will look at sets of siblings from a wide range of backgrounds, and compare their realized relatednes and their life outcomes. Remember, though the expected relatedness of siblings is ~0.50, there is variation around this (two of my siblings are related at ~0.41). We can use this information to gain more precisely a sense of the magnitude of genuine random contingency. My own suspicion is that a non-trivial component of the dynamics which are of such grave concern, that is, the suboptimal outcomes of children from single parent households in relation to married households, will be found to be heritable in a genetic sense. On the other hand, if sibling relatedness has no relationship to outcomes of the siblings, then perhaps the genetic component is trivial. So either way, we’ll know.

One can make an analogy to what I think might be happening via religion. In many societies in the past, and today, religious identification was or is obligatory as a social norm. Variation in religion identification in the society explained very little because there was not much variation. For most of American history the norm was to marry if you were in the top 3/4th of the socioeconomic distribution (with an ideal of a nuclear family, though this was realized by a smaller proportion because of divorce and death). Today that norm is receding up the class ladder. With strong social constraints removed it may be that personal dispositions, with a heritable basis, may be more predictive of marriage than was the case in the past. In other words, some component of the deleterious long-term effects of lack of marriage on children may be due to the correlation between not being married and particular personality types, with the latter being heritable.

As I suggest above the basic tools for these sorts of analyses are already there. We don’t need to rely on older behavior genetic designs which open themselves up for standard critiques. Rather, just look at the real genetic variation among full-siblings, and assess the outcomes of the full-siblings as a function of that genetic variation.

The explicit model of what I’m talking about is straightforward. People often look at parents and children, and look at the correlations between the marriages and life outcomes across the generations. These are real dynamics, in particular life outcomes (e.g., no debt graduating from university vs. lots of debt makes a huge difference in path dependency). But, people often don’t recall that personal dispositions impact marriage and life outcomes, and those dispositions are somewhat heritable! This does not mean that traits are genetic & fixed, look up what heritability means. But public policy responses are often neglectful of the heritable component. I would argue that this may make sense insofar as in the recent past the heritable component was less salient than it is today. In concrete terms the sociological version of H. economicus may be the problem, where all individuals can serve as substitutes in the models, even if the same social conditions result in radically different outcomes due to different dispositions (or, perhaps, a release of constraint of social conditions!).

MORE ABOUT: Behavior Genetics
  • Isabel

    I’m excited that we will be eventually able to see which parts of the chromosomes are shared by various siblings, and how random the inheritance actually is (why do some characteristics, from particular ancestors, seem to persist through the generations more than others? Is that an illusion?) and how much variation there is in relationship. Interesting, but not surprising, that two of your siblings are at 0.41.I’m from a large family and there has been wide variation in “outcome” in my siblings, and nieces and nephews (and it does not correlate at all with IQ!)

    I’m also curious to know how many generations it takes for some ancestors to fall out completely from the genome and become an ancestor on paper only, but I guess we will have to wait at least a couple of generations for that since we can only test 3 or 4 generations at most today.

  • Karl Zimmerman

    All things considered, I’d expect the heritability of marriage to be far lower than general personality traits. After all, two people are involved in a potential marriage. Presumably quite often people with a neurotype which tends toward stability will be drawn towards those who tend toward instability. I can say from some personal experience that attraction to a certain kind of whimsical, free-spirited, but fairly irresponsible person can be intoxicating in the moment.

    On the other hand, you could view it as showing a “bad marriage” is highly heritable, once you discount for spousal factors. Indeed, it’s entirely possible that the problem of broken marriages and single parenthood could be halved merely by people becoming knowledgeable about the traits which are likely (in a spouse) to lead to disaster.

  • Razib Khan

    #2, to be clear, i’m suggesting that the correlations between family-type and later life outcomes are possibly lower once you account for genetic factors.

  • Darkseid

    i thought it was interesting that single parenting could explain up to 40% of the income inequality gap. so the estimates normally published weren’t taking into account how many actual earners were in the house? they were only calculating how much total was earned? that seems like a pretty important thing to leave out.

  • Dwight E. Howell

    While in general terms you may well find a suit of genes connected with single female parents I’m inclined to suspect that the socioeconomic climate that gives these women the opportunity to raise their families sans spouse may be temporary and about to vanish.

  • Raimo Kangasniemi

    5. Throughout recorded human history there have been working, single female parents. For today’s “opportunity” read yesterday’s “necessity”. Married couples who both survive and stay together until the children are adults have not been the standard in human history.

    Not that it’s an opportunity often even today. Sometimes people – both women and men – need to raise their children alone for various reasons. These can – beyond the deaths of the other parent – be complicated and beyond the control of the single parent.

    To connect it to the genes of the single parents is simplistic. One could as well try to look at the genes of the other parent of the child or children in question and ask is there something in there that sticks out? And so on.

  • wijjy

    The data may already be collected for some of this. In the Visscher paper (ref below) that introduced this technique for looking at the heritability of height, text from the article:

    >Phenotypes for the adolescent cohort were collected in the context of continuing longitudinal studies >examining risk factors for melanoma [44] and cognitive functioning [45].

    After another six years since publication (possibly > 8 since collection) some aspects of life history could be examined (assuming ethics approval). Shared ancestry has already been calculated for these siblings.

    Visscher PM, Medland SE, Ferreira MAR, Morley KI, Zhu G, et al. (2006) Assumption-Free Estimation of Heritability from Genome-Wide Identity-by-Descent Sharing between Full Siblings. PLoS Genet 2(3): e41. doi:10.1371/journal.pgen.0020041

    #6 The idea with this is not to find genes. It is to test whether siblings with more shared ancestry have more similar life history outcomes to siblings with less shared ancestry. If so this implies that it must be due to genes. Which genes it is may be more difficult, or even impossible, to find. If you test parents then you potentially mix up environmental and genetic factors.

  • April Brown

    It would also be nifty if you could get this sort of sibling data from populations where extended family living situations are the norm, where even if the parent is single there are still aunts and uncles and grandparents in the same house participating in child rearing, instead of just a single working parent. Not sure if that would help prove anything, but might shed some light on whether there’s a difference in, say, number of caretakers in the home vs. whether or not the caretakers are the direct biological parents in a stable marriage.

  • Raimo Kangasniemi

    8. Isn’t that just basically a variation of the often tried study of twins?

    I wouldn’t say that you can’t get solidly away from non-genetic outside influences with non-twins siblings, but I would say it would be very hard to find and get rid all of the non-genetic “noise”.

  • Razib Khan


    1) the twin designs are the older designs that i am alluding to. they are open to criticisms, which you vaguely are aware of.

    2) read the paper i linked to above. your opinion is basically useless and uniformed otherwise. if you are going to offer your opinions on the credibility of genetic studies it behooves you to familiarize yourself with the literature, especially when is freely available.

    3) as i said, generic non-value added opinions are not welcome. last warning.

  • Darkseid
    this says they value marriage just as much. so what do we conclude? they’re just worse at being married or choosing partners?

  • Riordan


    Dont’ know if this sounds like pseudoscientific blather, but might it be possible that not only the success and failure of young marriages have a high factor of heritability, but also the fact of having children while young (<25 years of age), in both wedlock and out of wedlock, can also be traced back to familial genetics as well? I.e. certain individuals are hardwired differently neurologically speaking while young, or having higher hormonal drives, etc. that make them seek out "mates" for reproduction in either "traditional" forms such as marrying young and having kids or becoming single parents.

  • Razib Khan

    #12, well, the issue with direct selection on reproductive tendencies is that they often have lower heritability. that’s cuz genetic variation should be ‘squeezed out’ of the population. OTOH, one can i suppose suggest frequency dependence, so that different ‘morphs’ persist in the population. i think a more parsimonious explanation is simply that some personalities ‘express’ differently in different environments. for example, the ‘demographic transition’ isn’t a phenotype under selection, but obviously it has roots in particular human instincts which allowed for this radical change in behavior….

  • AndrewV


    Possibly both have correlates, but going down that path could also possibly lead to some unpleasant conclusions with detrimental political consequences.

    Better to keep the focus on personal dispositions, with a heritable basis yes?

  • Riordan

    @#11(Darkseid) and #14(AndrewV),

    Perhaps. More likely, I wonder if they represent a significant subset of the population whose culture, norms, if not hereditary biology are “stuck” in 1950s if not the 1900s. You can certainly view them as less intelligent and less capable of choosing and sticking with good mates, or you could see them as essentially(perhaps tragically ) maladapted for a post modern 21st century world. The witch’es brew of a more complex and faster daily life, an a la carte social environment of choosing and mixing your own bewildering behavior norms, coupled with downward economic pressure on wages, benefits, and jobs in addition to ever demanding roles for constant education/training would definitely exert a corrosive toll cognitively and psychologically even on the brightest and most intelligent, let alone those less neurologically sophisticated or personally modern. Hence why all those “marriages” and relationships collapsing in those working to lower middle class youths, either due to those external factors or personally between couples as a manifestation of those stresses. These factors may play a much larger role than simply being “incompetent’ in the mating market.

  • Karl Zimmerman

    The point could be made that choices to be a single parent/have children young are based upon a semi-rational appraisal of self-interest.

    Many long-time unmarried black women (both parents and non-parents) report a desire to get married, but cannot find a man they deem worthy. Which isn’t surprising given black women tend to have a higher level of education than black men, and the wage gap between black women and men is smaller, meaning it’s far more likely a woman will make more than her potential partner. Add in high levels of incarceration, and the greater likelihood of black men to date outside their race, and the available pool of quality partners is comparably small.

    Similar dynamics could operate among unmarried mothers is general – particularly because the phenomena of husbands relatively equally sharing chores and child-rearing seems to be a middle-class thing in the U.S., meaning if a husband is not making much money he’s probably not doing much to materially support his spouse at all.

    As to having children at a younger age, if a woman makes an assessment that their career options will be limited (due to “not being college material,” being unable to afford further schooling, or something similar) there really is no reason not to have a family right away.

    Indeed, these choices only seem like poor ones if you adopt a “blank slate” perspective – if you assume that all potential marriages provide the same material advantages, and that every woman who foregoes having children until their mid 30s will be able to ascend far in their professional life. The single mothers are probably making, to some degree, a better appraisal of their lives than the media is.

  • Isabel

    KZ @16: Very interesting comment and makes one wonder- when we stop focusing on female choice, what do we see going on in the males??

    “Similar dynamics could operate among unmarried mothers is general – particularly because the phenomena of husbands relatively equally sharing chores and child-rearing seems to be a middle-class thing in the U.S., meaning if a husband is not making much money he’s probably not doing much to materially support his spouse at all. ”

    Agreed, not getting married in this environment may not be such a bad decision. And what if the males are themselves not rushing to get married, even if outside of their race or whatever? This is part of a social trend, and puts a real additional burden on the female.

  • Raimo Kangasniemi

    This conversation don’t seem to have much to do with science, but voicing prejudices against minorities and social classes. It’s an utter nonsense that the choices of marriage or not and being single parent or not today could have much to do with hereditary genetic roles. The changes affect far too many people whose ancestors had quite different arrangements themselves so that any hereditary disposition could really be behind it.

    If we look at statistics at the age of marriage and the age of getting first child for both women and men historically, we find that the beyond the influence of cultural-religious habits, they are tied with the economic situation. The better it is, the earlier people marry, the earlier they get their first child whether in marriage or out of it, and the more children they will produce as long as child mortality remains at the same level. If it falls, people produce less children (or, like in some cultures from ancient Greece and Rome to numerous hunter-gatherer societies around the world, they kill the “extra” children).

    Inside same cultural-religious traditions, in the same regional areas, in same social classes, there is great variability that is explainable purely through changing economic situations. Studies of the peasants of Piedmont for example show this very well. If people could marry early and get children early because their economic conditions allowed it, they did so. If not, the average age at marriage of women rose at one point in one area to 30 among peasants.

    Different social classes have also different family strategies to provide for the family’s survival both to next generation and at least in it’s current position in social hierarchy. These are tied also to changing economic situations and they change with time. And they also change so often and so drastically, that no way can hereditary issues play much role on average in the question of marriage or no marriage and the decisions of when and in which arrangement children are produced and brought up.

  • AndrewV

    My poor attempt at a “dog whistle” @ #14 is that certain areas of research appear to need squid ink, for example “Human Genome Project Announces That “Race” Does Not Exist”.

    @#17, The “manosphere” calls it a marriage strike by men. This is not an unanimous assessment, for example Dalrock posited that it is women delaying/forgoing marriage in the first place.

    What men in general appear to be doing, is adapting different strategy given that the traditional societal structures around marriage are apparently deteriorating rapidly.

    Divorce rates are between 40% to 50% depending on how you view it, and it is not inconceivable that a large number of men, having observed the financial and emotional impacts, and the generally hostile environment to men in general during the process have reacted accordingly.

    Having gone through a divorce myself, I have advised my male offspring to:

    – Learn Game if they want sex. and avoid marriage and children (including single mothers).
    – Leave the country or import a wife if they want family, marriage, and kids.

    Of course, if I had female offspring, my advise would have been different.


  • AndrewV

    @#18, You just proved my assertion for the need for “squid ink” with your very first paragraph.

    What part of people often don’t recall that personal dispositions impact marriage and life outcomes, and those dispositions are somewhat heritable did you not understand?

  • Razib Khan

    It’s an utter nonsense that the choices of marriage or not and being single parent or not today could have much to do with hereditary genetic roles.

    look, this is false. if you read a genetics blog, you should at least know a little bit of the genetics whereof you speak. i can’t countenance the spread of false information. goodbye.

  • Sandgroper

    Andrew V. – An interesting comparative study is USA vs Australia. Divorce rates are the same (interestingly, divorce rate for second marriages is about 60-70% – apparently, people get worse at it with practice) despite some evident differences nationally in e.g. religion. I predict if you lived in Australia, the correct advice to male offspring would be the same.

  • Karl Zimmerman

    Although I know that you have banned him, I’d actually argue the reverse of 18. Lower rates of marriage, and delayed age of marriage, are at least in part due to the greater wealth in the modern west compared to traditional societies.

    Think about what life was like a century ago before modern labor-saving devices like dishwashers, laundry machines, and microwaves. Maintaining a life alone would be incredibly hard for anyone – doubly so in the period before normal work hours were reduced to the current 40 hours. It’s little wonder that those men who spent part of their life living with neither parents nor wife chose rooming houses where laundry and food was dealt with for them. Especially for the working classes, the economic benefits of marriage were just too great to forgo for long.

    It’s little surprise that the “bachelor pad” came into being as a concept in the 1950s – precisely when these labor-saving home appliances became affordable. Women living alone took a longer to become acceptable for social reasons, but the same basic dynamic applies. Technology – and wealth – made being single equal or sometimes preferable to married life. Hence the standards of who to marry – and when to marry – have climbed steadily upward.

  • AndrewV


    Thanks, we are very much aware of the situation in Australia thanks to people like Doctor Greg Canning who recently resigned from James Cook University. In some respects it is further along the way than the UK and N.America though.

    divorce rate for second marriages is about 60-70% – apparently, people get worse at it with practice)

    I tend to view that as the triumph of optimism over experience :) We need to study these people!

  • Sandgroper

    Yep – but not too close, in case it’s caused by a virus 😛

  • Sandgroper

    No doubt your informant has informed, but in Australia there are financial incentives not to get married – married individuals are taxed separately, and there are social service payments for single parents. So basically, married couples are subsidizing single parents and unmarried couples who fake single-parenthood through their tax payments.

    Hong Kong is the reverse – married couples are taxed jointly. So if you have a lower earning spouse (wonderful old fashioned word that has disappeared in officialese in Oz, to be replaced by ‘partner’, or even ‘current partner’), it can push you down into a lower tax bracket while not necessarily elevating your spouse into a higher one. Plus there is a tax allowance if you have a spouse. So there is some financial incentive to get married and stay that way. I think this is just the system mirroring what has happened in society, but it tends in the direction of self-reinforcement.

    That plus other radically different financial structuring seems certain to lead to significant (there’s that word again) societal differences, even discounting all of the other relevant factors. And I’m certainly not discounting heritability/environmental/cultural factors – the casual observation that kids from broken homes have trouble establishing stable relationships seems to hold, from what I see, if anecdote has any value at all.


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

Gene Expression

This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at


See More


RSS Razib’s Pinboard

Edifying books

Collapse bottom bar