In Nature, Plenty of Animals Pass the Paternity Test

"Ultimately, these things come down to costs versus benefits," said French in Omaha. "If the benefits in terms of offspring survivorship outweigh the costs to fathers, such as lost mating opportunities with other females, then natural selection will favor paternal care."

That rule applies equally to Homo sapiens -- albeit with a thick overlay of cultural influences -- and, all told, human males have generally found that fathering works for them.

Studies of indigenous tribes in Africa and South America have revealed extremely high levels of male parenting. Fathers Direct, a British nonprofit group, gave its "Best Dads in the World" award last year to the Aka pygmies of west-central Africa.

"The Aka are incredibly involved dads," said Barry S. Hewlett, an anthropologist at Washington State University. Fathers either hold or are within arm's length of their infants almost 50 percent of the time, he said, and they even let crying tots suck on their nipple to mollify them until Mom comes.

The Aka lifestyle, in which men and women hunt together, is conducive to sharing the load, and Hewlett cautions that direct care should not be seen as the only way to be a good dad. In Western industrialized cultures, he said, a dad with a steady job can be as stabilizing a force as a diaper-changing stay-at-home.

But in part because more women are working -- and more men are working from home -- direct care by fathers is growing fast worldwide, with Sweden topping the list among developed countries.

"Moms are still doing the lion's share, but the changes are undeniable," said Michael Lamb, a professor of psychology at the University of Cambridge. ". . . Thirty years ago, the dad who changed a diaper was seen as a fairly far-out character. Today, the dad who doesn't is seen as a dinosaur."

So move over, giant water bug. Homo paternicus is on the rise.

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