Med thumb father and infant in bed

Ever since we posted Jonathan David Stern’s wonderful account of how co-sleeping affected his marriage, I’ve been searching for information about how the act of sharing a bed with a young child might affect fathers. My curiosity doesn’t stem from any desire to practice co-sleeping whenever I have children — I’m against the practice for both safety and psychological issues — but rather from the fact that most studies focus on the mother-child bond. Does cuddling with a child have a positive effect on dad?

In 2012, Lee Gettler, an anthropologist at the University of Notre Dame, studied the testosterone levels of Filipino men both before they had children and four years afterwards. As recounted in Scientific American, the new dads who nodded off on the same surface as their offspring saw a rather steep drop in T-levels. Researchers thought it might have something to do with the fact that their sleep is disturbed several times a night. 

The Scientific American article suggested that, based on previous studies that show the most caring fathers often have lower T-levels, co-sleeping makes men better fathers. Quoting Gettler, “Lower testosterone might orient men more toward the needs of the partner and children and away from risky behavior and competition with other males — which could conflict with investments in parenting.”

Taking things further, I found a 2013 study that said that men with smaller testicles make for more nurturing fathers. In the study, researchers asked 70 fathers of young children to look at various images of their own children, as well as of other children and adults. As they viewed the images, an MRI scan recorded brain activity. Researchers also asked participants’ wives to answer questions about their husbands' child-rearing ability, including issues such as taking days off to care for sick children and involvement with baths and feeding. Testes size and T-levels were noted.

“Men with smaller testes, and men with lower testosterone levels, were more involved in the day-to-day caregiving of the child,” lead study author James Rilling told Healthline when the research was made public.

While the study offers a rather loose definition of a "good" father, it makes an interesting point about lower T-levels and caregiving: Researchers posited that while high levels might be important for proving worth during the courting period, lower T-levels, a result of smaller testes, are beneficial for parenting. 

What’s the point of any of this? If the act of co-sleeping helps lower T-levels, it could help young fathers become more fluent in the language of nurturing. It’s not something we recommend, but it is something for alphas to think about.