Behavior is heritable you know….

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Genes May Explain Why Children Who Live Without Dads Have Earlier Sex:

Mendle and her colleagues looked at more than 1,000 cousins ages 14 and older from the National Longitudinal Survey of Youth. The study design tested for genetic influences as well as factors such as poverty, educational opportunities, and religion. It compared children who were related in different ways to each other, and who differed in whether they’d lived with their fathers. The more genes the children shared, the more similar their ages of first intercourse-regardless of whether or not the children personally had an absent father. This finding, the researchers say, suggests that environmental theories don’t fully explain the puzzle. Instead, genetic influence can help us understand the tie between fathers’ absence and early sex.

“While there’s clearly no such thing as a ‘father absence gene,’ there are genetic contributions to traits in both moms and dads that increase the likelihood of earlier sexual behavior in their children,” notes Mendle. “These include impulsivity, substance use and abuse, argumentativeness, and sensation seeking.”These traits get passed down from parents to children, resulting in a situation known as ‘passive gene-environment correlation,’ because the same genetic factors that influence when children first have intercourse also affect the likelihood of their growing up in a home without a dad.”

This issue is known to anyone who has read Judith Rich Harris’ The Nurture Assumption. Nevertheless a lot of the psychological and social research published today routinely ignores the possibility of passive gene-environment correlation from what I can tell. Of course heritable propensities express themselves in an environmental context, so for example the rank order of average age of first intercourse among a set of unrelated families may remain the same in a Mormon “treatment” as opposed to a Wicca treatment (this is a thought experiment obviously), but the average age for the two cases would probably differ somewhat.



  1. I agree with the heritability argument for explaining (partially) cross-sectional data, but of course longitudinal changes over short periods–such as the huge changes in marital behavior, delinquency, adult crime, dropout from the labor force, etc., over the last half-century, are pretty hard to explain by appealing to changes in the genetic makeup of the population during the same period. Gotta keep both parts of the equation in mind.

  2. Sounds like that one needs a lot more study. For instance, might the operative genetic component not be more related to some other physical similarity (such as, for instance, age at onset of menses–which, in turn, I believe, is related to body weight)? The size of the study also seems extremely small. Remember, some significant proportion of “first intercourse(s)” will likely be between siblings, half-siblings, and cousins–simply, in many cases, as a result of proxmity and access. If these are included, it uneccesarily adds to difficulty in isolating actual causation, as well as increasing the likelihood that some other aspect of relatededness is the responsible (or more responsible) one.