The Scientific Fundamentalist

A look at the hard truths about human nature.

Why are mothers better parents than fathers? Part I

Mommy's Baby, Daddy's Maybe?

“Mommy’s Baby, Daddy’s Maybe”

In a climactic scene in the 1999 horror movie The Blair Witch Project, Heather Donahue’s character, sensing her and her friends’ impending deaths in the woods, turns the camera on herself and says “I just want to apologize to Josh’s mom, and Mike’s mom, and my mom.” Given that her film project eventually led to Mike’s and Josh’s (as well as her own) deaths (sorry for the spoiler), an apology might make sense. But why did she apologize to their mothers, and not to their fathers?

The answer, from an evolutionary psychological perspective, is that Heather instinctively knew, as do most of us, that children are more important to their mothers than to their fathers, and, as a result, their loss would be more devastating to their mothers than to their fathers. It is not difficult to find abundant evidence for the fact that mothers are more dedicated to their children than fathers. For example, when married couples with children get divorced, chances are that the children stay with the mother, not the father, especially if they are young. According to the 1992 March/April Current Population Survey in the United States, conducted by the US Census Bureau on a nationally representative sample, 86% of custodial parents are mothers. Further, many of the noncustodial fathers who have agreed to pay child support, either voluntarily or via court order, default on their commitment and become “deadbeat dads." The first national survey of the receipt of child support, conducted in 1978, reveals that less than half (49%) of women awarded child support actually received the full amount due to them, and more than a quarter (28%) of them received nothing. The percentages have remained more or less constant since. In 1991, 52% of custodial parents awarded child support received the full amount; 25% of them received nothing. So the question remains: Why are women so much more dedicated parents than men? Why are there so many deadbeat dads but so few deadbeat moms?

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On the surface, this massive sex difference in the dedication to children may appear puzzling, since both the mother and the father are equally related to their children genetically; each parent transmits half of their genes to their child. However, there are two biological factors that combine to make fathers far less committed as parents than mothers.

The first is paternity uncertainty. Because gestation for all mammals (including humans) takes place internally within the female’s body, the male can never be certain of his paternity, whereas maternity is always certain. And paternity uncertainty is not a remote theoretical possibility. As I mention in a previous post, the estimated incidence of cuckoldry (men unwittingly raising and investing in another man’s genetic offspring) in contemporary Western societies is substantial (between 10% and 30%). Thus, this is a very realistic possibility for any father in contemporary Western society and probably elsewhere throughout human history as well. Naturally, men are not motivated to invest in children who have a distinct possibility of not being genetically theirs.

The twin concept of paternity uncertainty and maternity certainty is captured in the common saying “Mommy’s Baby, Daddy’s Maybe.” Every single mother, not only among humans but among all mammalian species, has been certain that the child that she has just given birth to is hers; no woman has ever wondered, as a child is coming out of her body, “Hmmm.... I wonder if this child is really mine....” In contrast, every single father wonders, either explicitly or implicitly. Some wonder more than others, but no father has ever been completely certain of his paternity. The best he can ever say is “Maybe.”

So paternity uncertainty is the first reason why fathers are less dedicated to their children than mothers. I’ll discuss the second reason in the next post.

Satoshi Kanazawa is an evolutionary psychologist at LSE and the coauthor (with the late Alan S. Miller) of Why Beautiful People Have More Daughters.

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