Satoshi Kanazawa

The Scientific Fundamentalist

Why are mothers better parents than fathers? Part III

Is Tommy Smothers right? Do parents play favorites?

Posted Jun 19, 2008

In the last two posts (Part I, Part II), I explain why mothers are on average more committed and hence better parents to their children than fathers. However, this does not mean that mothers are always better parents; there are exception. Even then, however, evolutionary psychology can shed light on the exception which proves the rule.

None of what I have discussed in the previous two posts mean that all mothers are always good parents or better parents than fathers. Sometimes mothers neglect or even kill their babies. However, evolutionary psychological logic can even explain who is more likely to kill their babies, and why.

Statistics show that very young mothers, by far, are the most likely to kill their babies, and older mothers are the second most likely to do so, but for different reasons. Very young, teenage mothers kill their babies because they still have most of their reproductive lives ahead of them, and they can make more babies in the future even if they kill the one they just had. Having a baby under unfortunate circumstances (such as without a father willing to invest in it) not only threatens the well-being of the baby but also jeopardizes the mother’s chance of finding a mate in the future. And teenage mothers are more likely than others to have their baby under unfortunate circumstances.

Older mothers (above the age of 35) kill their babies for a different reason. They are more likely to have defective babies because of their age. Every child (defective or otherwise) consumes parents’ resources. Since defective children are much less likely to attain reproductive success, from a purely genetic point of view, any resources invested in children who will not have children themselves are wasted. Such children are taking away valuable resources from other children who have better reproductive prospects. Older mothers are more likely than younger mothers to have other children they must also raise. So parents are designed not to invest in defective children.

By the same token, parents invest more in better-looking children than in less good-looking children, and in more intelligent children than in less intelligent children. Without necessarily knowing it consciously, parents do favor some children over others, and the extent to which they favor some children is strongly correlated with their likely future reproductive success. They usually favor children who have better future reproductive prospect over children who have gloomier future reproductive prospect. In other words, Tommy Smothers is right. Mom did always like Dick best. (Pardon the grammatical error.) According to the Smothers Brothers official biography, Tommy has had three children; Dick has had six.

Yes, the evolutionary logic is very brutal, cold, and heartless. It only cares about the survival of the genes.