Ever wondered why some men who are fathers are more adept caregivers and actively involved with the hands-on care of their toddlers than others?
According to an intriguing new study, nurturing fathers have lowered testosterone levels. Researchers found men with smaller testicles tend to be more involved as fathers and invest more time in parenting.
Earlier studies have suggested that decreases in testosterone may stifle mating efforts, which may serve as a trade off for directing a man’s energy toward the care of infants.
“I wouldn’t want to say that men with large testes are always bad fathers but our data show a tendency for them to be less involved in things like changing diapers, bathing children, preparing meals, taking them to the doctor and things like that,” said lead author James Rilling, an associate professor of anthropology at at Emory University.
Details of the study
The aim of the study was find a deeper biological basis for nurturing behavior and to examine the role of fathers in child care. They decided to evaluate the link between testes size and parenting in men.
For the purpose of the study, experts enrolled 70 biological fathers aged between 21 and 43 years. The men, mostly married were living with the new born kids and their biological mothers during the study period.
In order to assess the father’s involvement in childcare, both parents were interviewed separately and asked questions pertaining to the father’s daily hands on involvement (tasks like changing diapers, bathing the child, healthcare visits) with care of the infants.
Additionally, they used fMRI brain scanners to monitor the brain activity of the men while viewing photos of their kids. They also measured the testicle size of the men volunteers.
The study found region of the brains associated with caring and tenderness light up more strongly in men with smaller testes at the sight of their kid’s emotional faces in pictures than those with larger ones.
Riling stated, “We’re assuming that testes size drives how involved the fathers are, but it could also be that when men become more involved as caregivers, their testes shrink. Environmental influences can change biology. We know, for instance, that testosterone levels go down when men become involved fathers.”
The findings were published in the journal Proceedings of the National Academy of Sciences.