Sexy Sons Make Fathers Seem Sexier
Have you ever heard of the ‘sexy son’ hypothesis? It’s the idea, first mooted 85 years ago, that females should choose a male capable of giving her sons who, in their turn, will be reproductively successful. That the best male for a female to mate with is one who will give her sexy sons. The hypothesis has been studied in a wide variety of animals, and it explains the evolution of bizarre male ornaments across the animal kingdom.
Imagine a species of male bird with an especially long tail, and that males with longer tails are more adept at flying. Females will be better off if they mate with a long tailed male, because their offspring will inherit the genes that code for long tails. However, over time the female preference for long tails grows stronger, until at last it is self-reinforcing. Now it doesn’t matter if males have evolved tails so long that they are cumbersome and actually pose a handicap for flying. The females will choose long-tailed males simply because they find them attractive, thereby guaranteeing they’ll have sons who are equally sexy to the next generation of females. In the end, you might be left with a tail as ludicrous as that of a peacock. A peacock’s tail doesn’t help its owner to fly, but peahens sure do find them sexy.
Anyway, why this primer on evolutionary biology? Well, I was reminded of the sexy sons hypothesis this week when I read a new paper by Pavel Prokop of Trnava University in Slovakia. Prokop points out that most research on human mate preferences concentrates on the period of time before mating occurs. In other words, how people meet each other and decide to give it a go. But, it might be just as important to study post-mating preferences. How we feel about our partners after we have been with them for a while, and even after we have had children with them. After all, choosing a mate is also about the choice we continually make to stay with that person.
So what does this have to do with sexy sons? Well, one of the ways women might decide whether a man really is a catch is by examining his offspring. When you first meet an attractive man, you might think, “hey, his genes plus my genes will equal some cute looking kids”. Once a man has fathered a child, though, you no longer have to guess. The evidence is there for all to see. And if you’ve popped out a gargoyle it might be time to ditch your feller.
Prokop collected photographs of around 120 White boys between the ages of 4 and 5, and around 80 White men between the ages of 22 and 30. He had all the photos rated for attractiveness. There are no doubt some of you who think it’s a bit weird to rate boys’ faces for attractiveness and, yeah, you’re probably right. Anyway, that’s what Prokop had his volunteers do. Let’s just go with it, shall we?
Next, he discarded all the photos that received mediocre ratings, retaining only the top 20 most attractive faces from each group, as well as the bottom 20 least attractive. Then he paired each adult face with a child face and showed these pairs to a new set of volunteers. The volunteers were told that each represented a real life father-son pair. In reality, the men and boys were unrelated, and were paired up so that there were an equal mix of attractive and unattractive boys and men. The volunteers rated the ‘father and son’ in each pair for attractiveness.
Prokop found that pairing a man with an attractive boy made that man more attractive. That is, if he compared the attractiveness rating a man received when he was on his own with the rating that same man got when he was pictured with a good looking boy, it was higher when he was pictured with the boy. The effect was stronger when the man was unattractive to begin with. It was almost as if the volunteers saw the unattractive man paired with the attractive boy and thought, “This man isn’t exactly a looker, but if he can father a son who looks as cute as that then perhaps I’m missing something. I’ll rate him a bit higher than I ordinarily would.” Of course, there’s no indication that this process is conscious. Women are most likely using a quick rule of thumb to make their ratings.
And this is probably what got Prokop wondering what would happen if the volunteers were told the men and the boys weren’t really related. Maybe the effect would still work. Maybe seeing a cute child puts women in a positive frame of mind and they rate the man more highly for that reason alone. If so, the effect of the child’s attractiveness on that of the man would have nothing to do with whether women are judging a man’s ability to father cute kids.
Prokop had another set of volunteers repeat the study, and this time he told them that the men were the stepfathers of the boys. This way he could keep the experiment exactly the same, except that now volunteers were not under the impression that the men were the genetic fathers of the boys. This time, there was no effect of the boys’ attractiveness on the attractiveness ratings of the men. Meaning that the idea that the men and boys were related is necessary for the effect to work. Women really were adjusting how they perceived a man’s attractiveness based on the attractiveness of his kids.
Prokop, P. (in press). The putative son’s attractiveness alters the perceived attractiveness of the putative father. Archives of Sexual Behavior. Read summary
The content of this post first appeared in the 21 April 2015 episode of The Psychology of Attractiveness Podcast.
