Score One for Faithful Dads

From Sharon Begley's WSJ science column of yesterday ($) comes an evolutionary pat on the head for faithful dads (emphasis mine):

At first glance, the "sexy son hypothesis" makes perfect sense. According to this pillar of evolutionary biology, a female who chooses a high-quality male will have sons who inherit dad's allure. They, too, will therefore have their pick of females, allowing mom to hit the jackpot: grandmotherhood.

But when scientists followed male flycatchers whose dads were real catches (as judged by a forehead patch that is this bird's equivalent of perfect abs), they found no such thing.

The sons "did not inherit their father's ... mating status," the Swedish researchers wrote in the February issue of American Naturalist.  As a result, mom got fewer grandkids than did females who settled for less-attractive males.  The studs were so busy mating they had no time to raise offspring, causing their health and fecundity to suffer.  Homelier birds were better dads, raising sons who had more mating success.

I read something similar a few years ago in journalist Robert Wright's 1994 book The Moral Animal.  He noted that, to be sure, promiscuous males have a better chance of passing their genes on to children.  But when a father sticks around to help raise the children, that improves the chances that the children will survive to adulthood.  Consequently, other things being equal, a faithful father raises the odds that both dad's and mom's genes will be replicated not just in children but in grandchildren.  (Once again, life isn't a snapshot, it's a movie.)   So over time, we would expect that the population would be increasingly made up of females who prefer to mate with faithful males and of males who are prone to be faithful.  The Swedish researchers' observations are consistent with the first part of this prediction.