While many of us are well aware of hormonal changes and their effects in pregnancy and new motherhood; we don’t often hear of the physiological effects a man’s body undergoes as he becomes a father. But doesn’t he just “supply his genetic material” and mom does the rest? No, fatherhood actually changes a man’s physiology too. And these changes indicate the biological importance of active fathering. Research shows that a man’s testosterone levels are significantly affected by fatherhood; and—even more striking—by the quality of his interactions with his child.
A large study showed that men’s testosterone levels decrease with fatherhood. For the 600 men in the study, testosterone was measured at the age of 21 when the men were single, and again nearly five years later. Those who had become fathers in the 4.5 years between check ups had higher baseline testosterone (T) levels compared to those not partnered with children by the second check up. However, the testosterone levels of partnered fathers declined significantly more (2 times more) than the non-fathers, suggesting fatherhood lowers testosterone levels (this even when natural age-related testosterone declines are accounted for).
What’s even more fascinating is that the men who spent three or more hours with their children each day—playing, feeding, bathing, diaper changing, reading or dressing them—had even lower levels of testosterone compared to fathers less involved in care.
Now, many men believe that more testosterone is better, so before getting bummed about these findings, let’s talk about the benefits in this hormonal change of fatherhood.
Lower testosterone levels increase the likelihood that men will remain committed to their family and be involved in a care taking role with children. This study shows that women are not the only ones biologically adapted to caring for offspring. It indicates that men are biologically adapted toward an active care taking role within the family system.
“A dad with lower testosterone is maybe a little more sensitive to cues from his child, and maybe he’s a little less sensitive to cues from a woman he meets at a restaurant,” said Peter Gray, a University of Nevada anthropologist who has conducted research on fatherhood and testosterone.
Lower testosterone levels exhibited in fathers are significant but subtle in the big scheme of things. Researchers note that these fatherhood hormone “drops” are not enough to affect libido, sperm counts, muscle mass, voice range, body hair distribution/amounts, or all those other characteristics of the human man.
Lower testosterone may also provide some protection against disease. Studies show that higher lifetime testosterone levels increase the risk of prostate cancer, suggesting that fathers in committed fathering roles might have lower long-term exposure to testosterone and thus a lowered risk of prostate cancer.
This study shows that human males have adapted to have similar hormonal systems to other animal in which the males care for young, such as some birds and primates.