For men hunting for a partner, testosterone’s a good thing. It boosts competitive behavior, and increases men's attractiveness to women. But the hormone has its drawbacks. Men with more of it have more marital problems and divorces. One study even suggested that guys with high testosterone have less sympathy for crying infants.
But there’s good news. Because having a kid appears to cut testosterone levels—essentially priming men to be better dads. So says a study in the Proceedings of the National Academy of Sciences. [Lee Gettler et al., "Longitudinal evidence that fatherhood decreases testosterone in human males," PNAS 2011]
The researchers sampled testosterone levels of over 600 21-year-olds in 2005, and again in 2009. And they quizzed them on their relationships in the interim.
Single guys with high testosterone had better luck finding mates by the study’s end, and were more likely to have become fathers. But their testosterone plunged, compared to peers who stayed single. And the more hours a day they spent with their kids, the lower their testosterone levels fell.
Which suggests that being a nurturing dad may have ancient evolutionary roots—and that men are biologically wired to shift from alpha-male to tender caregiver when bringing up baby.
[The above text is a transcript of this podcast.]