As a parent it is important to me that my daughter grow up in the context of a two-parent monogamous household. Not only do I find this arrangement congenial for a variety of personal reasons, it is also what society is most optimally set up for. But there is a strong class element today in the United States as to the realization of this ideal. While 94 percent of college educated women giving birth are married, 57 percent of women with a high school education or less are unmarried when they have their first child. These striking correlations emphasize to many social conservatives the importance of marriage in shaping individual outcomes.* The lesson being that if you get get married and complete your education you will not be poor. What immediately comes to mind though is that those who do not get married and finish their education are not an arbitrary subset of the population. For example, they are less likely to have a range of personality traits which allow for trading off utility in the short term for gains in the long term. Giving someone a marriage license and keeping them locked in school may not change these underlying habits of mine and behavior. But this attitude toward the causes and dynamics at work in social ills is not limited to ideological conservatives. It is a widespread view informed by common sense observations. Though many individuals from broken homes do very well, on the whole it is clear from anecdotes and social science that this life history adds stress and diminishes life prospects.

Or does it? Over ten years ago Judith Rich Harris published The Nurture Assumption: Why Children Turn Out the Way They Do. Though the basic argument of the book, which draws from peer-reviewed behavior genetic literature, was outlined extensively in The Blank Slate, it has gotten very little broad cultural traction (though it occasionally pops into the public discussion thanks to economists such as Bryan Caplan and Steven Levitt, who see similar patterns as the behavior geneticists). The primary lesson is that main distinctive contribution parents seem to make to the outcomes of their children in a behavioral and social sense is their genetic contribution. This does not mean that behavioral traits are primarily genetic in terms of explaining the variation in outcomes. Rather, it means that the environmental contribution is not something that parents have much direct control over. In The Nurture Assumption the author proposes that the primary environmental causal factor are peer groups. Though this has not been extensively validated to my knowledge, it seems a plausible enough candidate. For example, children tend to speak with the accents and lexicon of their friends, not that of their parents. If upper-class parents from a particular region share linguistic characteristics with their offspring, it has little to do with the direct parental modeling, as opposed to being embedded in a common social milieu.

As the year progresses you will read a great deal in the press about sociological dynamics and how they effect individuals, often for the worse. In response conservatives will point to the importance of individual responsibility and collective norms in enforcing ideal behavior and life outcomes. Liberals will allude to various structural factors which set up people to make wrong choices, and various governmental solutions which might mitigate and even counter-act these forces. What both viewpoints will neglect is that much of the variation in outcomes in individuals, and across social sets, is likely due to heritable differences in personality. In plainer language individual differences matter, much of which is due to genetic differences. To illustrate what I am talking about, consider the robust correlation between children who are abused who abuse then their own offspring when they become parents. A commonsense explanation here is that inappropriate behavior was modeled, and the parents are now recapitulating what they learned. But one immediate issue that comes to mind is that parents who beat their children with no compunction may have a particular personality profile tending toward low empathy and lack of self-control. This personality profile is likely heritable, and passed to their offspring, who naturally exhibit the same characteristics.

The complexity of life outcomes is such that we must be cautious about how we appropriate the weight of a given causal factor on a social, let alone individual, level. When it comes to complex traits with a genetic component how that variation manifests on a social level is strongly conditioned by cultural context. In a society where physical punishment of children is highly normative abuse may not be due to any personality profile at all, because most people are conformist enough that they follow the broader script. Perhaps it is in societies where the norm is changing and not standardized where personal dispositions come most strongly into play as a factor. Similarly, when it comes to a social ideal like marriage obviously cultural headwinds were such that two generations ago no matter your personality profile the expectation of being wedded was so strong that most individuals fell into line. My point is that as you read story after story this year about the impact of various purely social forces in the media, do not neglect the power of genetic variation in many phenomena. It will give you a better and more complete understanding of what’s really going on, which is the point of it all in the end….

Addendum: Long-standing readers may wonder why I’m posting this, since it’s not particularly original. Because every now and then the unoriginal needs to be restated, because it’s actually original to many.

* It is critical to note that lower SES individuals actually value the idea of marriage as much, or more, than higher SES individuals. Rather, they fail to realize their ideal. Often the idealization of marriage manifests with individuals marrying after the birth of their first child, in some haste.