Older fathers are more deeply involved with their children's schools, more likely to attend ballet classes or know their children's friends.

On the other hand, the children of older fathers seem to have stronger genetic predispositions to schizophrenia and autism－so much so that older dads should get genetic counseling, Raeburn argues, just as older moms hear about the risk of Down syndrome.

On yet another hand, the children of older dads are taller and slimmer. So there's that. (Nobody knows why.)

As these examples suggest, father research cuts across disciplines, and Raeburn excels at mapping the twistiness of the road ahead.

Fathers are more likely to roughhouse, and rough play is good for children. But how much is this kind of "masculine" play in our dad genes, and how much does it come from cues that we pick up, then pass on, telling all of us that men do the rough play? If there is no father, but there are two mothers, does one mother become more likely to do the more dadlike play?

Raeburn is perhaps a bit too careful in withholding recommendations. A more argumentative book would have called, at least, for increased paternity leave, a corporate culture more supportive of all parents, and other policies to nudge dads into their children's lives. However, he makes a powerful case that fathers matter. Children can grow up happy and successful with just a mother, or with two moms. But we should attend to the benefits that fathers are more likely to bring.

After all, my wife would never have let the girls on top of the minivan.