Could Dads Actually Be Just as Hard-Wired to Parent as Moms Are?

I’m not someone who usually cries in movies, but since having my son, I’m a big baby. A touching family moment, a shot of a proud parent in the audience of So You Think You Can Dance – forget it. I’m more empathetic now that I’m a mom, and every parenting book tells me it’s because my brain is programmed to light up at my son’s distress, oxytocin, triggering my maternal caretaking behaviors, and so on. Thanks to nature’s plan to keep me dialed into my child’s needs, I’m wired differently now.

But my husband has changed too. On the one hand, he’s a bit more sensitive, tearing up like me at things that before would have prompted only a sarcastic comment. And in a strange parallel, he’s also more protective. He puts his hand on other people’s shoulders to make sure they get across the street safely. He daydreams about hypothetical escape routes from Los Angeles in case of a nuclear attack or zombie invasion (he watches a lot of sci-fi). He sneaks into our son’s room every night by the light of his cell phone and hovers his face in the crib watching him sleep. He’s a dad, and it has changed his brain.

The biology of fatherhood doesn’t get much play – dad manuals and parenting advice usually focus on how a man can support his partner and take care of her, so she can in turn take care of the baby. But it’s becoming increasingly clear that being a dad (and even preparing to be a dad) programs men differently, down to the level of brain cells and hormones.

It’s easier to test male brains in non-humans, so when scientists are studying the chemistry of fatherhood, they use animals that mirror our human tendency to form pair bonds and co-parent. The male marmoset monkey, for example, is predisposed to nurture, and his top priority is to clean, hold and carry the young on his back – picture a human dad washing the dishes while wearing a Bjorn.

When scientists look at the brains of these primates, they find that after mom gives birth, the dads actually grow more neuron connections in certain areas of the brain’s prefrontal cortex – regions involved in caretaking and bonding. After becoming fathers, they have more receptors for the chemical vasopressin, which is related to nurturing and attachment.

These dads also gain a significant amount of weight while mom is pregnant (the phenomenon translates to humans, say my dad friends). Not only that, male hormones change while mom is pregnant. Prolactin levels go up in the male marmoset and cotton-top monkeys during pregnancy. And after childbirth, human dads have a drop in cortisol and testosterone (which scientists think makes them less likely to fight and more likely to devote energy to caretaking).

And as Dad is changing, want to guess who else is being affected? Last month, a Scientific American article highlighted research that suggests babies change when dad is around. In a similarly domestic mammal with highly involved dads – the Deju rat – a baby’s brain needs the father around to grow normally. Without him, fewer connections are made between neurons in two crucial brain regions: the somatosensory cortex (which responds to touch) and the orbitofrontal cortex (a center of emotion and decision-making). It’s intriguing to think about the unique role of a dad, but we can’t be quick to translate this to humans and suggest that babies need dads to be healthy. Rats have smaller and more concrete brains that are programmed to attach immediately, whereas human babies are much more flexible and sophisticated – forming bonds with their caretakers (male or female) over the first years of life.

The research, however, is strong enough for us to assume that, in humans as in rats, dads and babies change each other. We tend to see characteristically maternal behaviors as the gold standard for attachment, but dads can have just as strong a drive to attach (for example, a recent study found that oxytocin levels rise equally in new moms and dads), even if the result looks different on the outside – moms’ soft cuddles and high-pitched “motherese” voices vs. dads’ physical play and a tendency to show objects to the baby.

But these are all attachment behaviors, and they all reveal a deeper biological drive to bond, teach, and care for our kids. My husband says that as a father he sees the world through a new lens – it’s part of his identity and he almost can’t remember what life was like before. Becoming a parent changes both mom and dad at the core.