Baby girls cause divorce

Some economics research hasshown, according to a new Freakonomics podcast:

Couples who conceive a child out of wedlock and find out that it will be a boy are more likely to marry before the birth of their baby.
Parents who have first-born girls are significantly more likely to be divorced.
Fathers are significantly less likely to be living with their children if they have daughters versus sons.
In any given year, roughly 52,000 first-born daughters younger than 12 years (and all their siblings) would have had a resident father if they had been boys.
Divorced fathers are much more likely to obtain custody of sons compared to daughters.

A 2003 Slate article also said daughters cause divorce.

I found this surprising at first, but there is a plausible evolutionary psychology explanation. Boys require much more investment for their eventual success. A mom is apt to think that she can raise the girl to be a marriageable woman without the dad. A boy is more difficult. See also this 2010 summary.

To the evolutionist, "survival of the fittest" really means survival of whatever results in more grandkids. If your purpose in life is to have grandkids, it is much easier if you have girls. You can be a terrible parent, and your girls turn out to be narcissist sluts, and you will probably still have grandkids. In fact, if you send the girls to graduate school to prepare them for some elite career, you are less likely to have grandkids. On the other hand, boys usually have to have a successful career to attract a mate and have kids.

It sounds unjust, but from this evolutionary view it makes much more sense for a family to invest in the boys, and not the girls. In particular, the parents need to stay married to do it right.

Schools and others in the USA treat girls much better than boys. Boys have more obstacles, and rearing a boy is more work. Moms are more likely to understand that they cannot do it alone, and want the dad investing in the boy's future so that he will successfully marry and reproduce some day.

The theory of evolution does not depend on anyone consciously using this reasoning, any more than it depends on fishes consciously deciding to crawl out of the water and live on land 100s of millions of years ago. The point is that if some people have genes and behaviors that lead to more grandkids, then those genes and behaviors will increase every generation.

To my surprise, the podcast did not mention this explanation. The research economist said that he could only think of three explanations, mostly having to do with dads not wanting daughters. But his three seem unlikely to explain anything. First, parents in the USA want daughters as much as sons, if you look at adoptions and other situations where the parents have a choice. Second, it is usually the mom who files for divorce, not the dad. If daughters are causing divorce, it seems likely that the moms are the ones deciding that the girls do not need dads.

Steven E. Landsburg wrote this followup to his Slate article:

A number of readers offered the comment that, evidence be damned, they would simply never believe that the children's gender could be relevant to a divorce decision. My favorite of these came from a therapist in Iowa — it would probably be inappropriate to mention her name, so let's just call her "Bozo the Therapist" — who took me to task for the "archaic notion" that children ever have anything to do with divorce. Unless she's been practicing not in the state of Iowa but on the planet Iowa in some distant solar system, Bozo must win the prize for "least observant therapist in human history." The fact is that children do affect divorce decisions; if we didn't know this from statistical evidence, we'd still know it from common sense. And to a smallish but non-negligible extent, girls cause more divorces than boys do. Ignoring those facts won't make them go away.

The facts are clear and worth reporting, but there's legitimate controversy about what they mean. There are three key facts: 1) Parents of daughters are more likely to divorce than parents of sons; 2) in multichild families, parents of daughters are more likely to try for another child than parents of sons; 3) divorced mothers of daughters are less likely to remarry than divorced mothers of sons.

I would not be surprised if most therapists are out-of-touch on this issue. They usually say that the cause of most marital problems is a lack of communication. Often it is kids, money, habits, values, etc. And sometimes it is too much communication.