Sociologists and demographers have discovered that the presence of sons decreases the probability of divorce.  Couples who have at least one son face a significantly lower risk of divorce than couples who have only daughters.  Why is this?

That couples with sons have a lower probability of divorce than couples with only daughters is even more amazing given the fact that, as I explain in previous posts, violent men and sexually promiscuous people are more likely to have sons.  I would think that domestic violence and sexual promiscuity (and extramarital affairs that result from it) would contribute significantly to the likelihood of divorce.  So why, then, are couples with sons less likely to divorce?

Recall that a man’s mate value is largely determined by his wealth, status, and power, whereas a woman’s mate value is largely determined by her youth and physical attractiveness.  This means that the father has to make sure that his son will inherit his wealth, status, and power, regardless of how much or how little of these resources he has.  A working-class father still has to make sure that his son will inherit what little wealth he has, because the more the son inherits, the greater his expected reproductive success.

In sharp contrast, there is relatively little that a father (or mother) can do to affect the daughter’s expected reproductive success.  Once she is born, there is very little parents can do to keep her youthful or make her more physically attractive.

The evolutionary psychological logic therefore predicts that the continued presence of (and investment by) the father is important for the sons, but not as much for the daughters.  Strictly in reproductive terms, there is very little that fathers (or anyone else) can do for daughters beyond keeping them alive and healthy.  The presence of sons therefore deters divorce and departure of the father from the family more than the presence of daughters, and this effect should be stronger among wealthy families.

Of course, strongly wedded to traditional social sciences as they are, the sociologists and demographers who discover that the presence of sons decreases the probability of divorce explain this finding by saying that fathers are considered to be more important for their sons’ lives than for their daughters’, and that the presence of sons encourages fathers to get more involved in child rearing, thereby lowering the likelihood of divorce.  Of course, they are right; fathers are generally considered more important for sons than for daughters, and the presence of sons does encourage fathers to get more involved.  But the social scientists cannot explain why this is so.  Evolutionary psychologists can.

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