The phrase “a mother's instinct” has been used to explain how new mothers seem to instinctively know how to carry for their newborn babies. But now a new study from Northwestern University offers strong evidence that men are biologically wired to care for their infants as well. Not only that, but the most recent research conclusively shows for the first time that fatherhood lowers male testosterone
.Nature knows raising a baby requires group effort.
We see this in the animal kingdom all the time. Other species have males that help take care of offspring. We also know that testosterone strengthens traits and behaviors that help make males more competitive when it comes to finding a mate. However, once they find one and become fathers, those behaviors that are related to mating may clash with the responsibilities of fatherhood. For that reason, it's advantageous for the body to slow down the production of the hormone.
Christopher W. Kuzawa, associate professor anthropology and co-author of the study said, “Humans are unusual among mammals in that our offspring are dependent upon older individuals for feeding and protection for more than a decade. Raising human offspring is such an effort that it is cooperative by necessity, and our study shows that human fathers are biologically wired to help with the job.”The role of testosterone in fatherhood.
Though prior studies have shown that fathers tend to have lower testosterone levels, it wasn't clear if fatherhood actually reduced
testosterone or if men with low testosterone
to begin with were more likely to become fathers. The latest study took a different approach by following a group of men that were not fathers and then seeing if their hormone levels were modified once they fathered a child.
Lee Gettler, co-author of the study, said, “It's not the case that men with lower testosterone are simply more likely to become fathers. On the contrary, the men who started with high testosterone were more likely to become fathers, but once they did, their testosterone levels went down substantially. Our findings suggest that this is especially true for fathers who become the most involved with child care.”
Fathers may experience a large, but temporary, decline in testosterone when they first bring their infants home from the hospital. It's a well-known fact that fatherhood and meeting the demands of a newborn require psychological, emotional, and physical adjustments
. According to the study, a man's biology is equipped to change so he can meet those demands.
Interestingly enough, the authors of the study feel their findings may help explain one reason why single men often have poorer health than their married counterparts with children. Surprised? “Lower testosterone levels” doesn’t necessarily have to be a bad
thing. In fact, it may offer some protection from certain chronic diseases.
So the next time you see a new dad melting at the sight of his newborn baby, or pitching in for diaper duty, it's more than just love at work here. Nature has a back-up system in place. Dad’s dwindling testosterone helps make sure baby is well taken care of.