Just in time for Father's Day, I'd like to say happy Mother's Day to all the dads out there. It turns out, you are more like her than you knew.
Long after the kids are grown and gone, a mother's body bears witness to pregnancy, childbirth and nursing. But researchers say the change may be most profound in her brain.
From earliest times — and in primates and other mammals — females have become more focused as a result of having offspring. They are increasingly aware of the environment and the dangers it presents. And they must find and maintain a source of food for themselves so they can in turn feed their offspring.
(This is considered to be the beginning of the multitasking that the modern woman is famous for. We are not amused.)
The female of the species becomes an even better mother after subsequent births. She is more bold and better able to handle new situations with less stress or fear. That's us, all right. The first-born probably doesn't recognize the woman who is mothering the second child.
We think that the change is all on the female side of the parenting equation, but it looks like men — mammals, primates and the guy you married — undergo physiological and hormonal changes as well, changes that make them better parents.
It is the validation we've been waiting for, isn't it? To be a good father, you have to be more like us mothers.
It looks like fatherhood changes the male brain and body just as it does the female brain and body, and those changes increase as males spend more time with their mate and child.
Testosterone is considered to be the reason fathers are more assertive in both discipline and play than mothers. But the more time males spend in the company of their mates and their offspring, they more likely they are to experience a drop in testosterone that is associated with more responsive parenting, according to research by scholars in the natural and social sciences that was assembled by Kathleen Kovner Kline of the University of Pennsylvania and W. Bradford Wilcox of the University of Virginia.
Even sympathetic weight gain is evident in primates — the better to store fuel for the increased energy demands of a baby. And second-time fathers are better at finding food and problem solving and are less vulnerable to distractions and more attentive to their mate and their offspring. They are even less likely to respond to the sex scent of another ovulating female.
It translates for humans as well. "What we are seeing now is when dads are in the home with their kids they benefit from that physically, socially and emotionally," said Mr. Wilcox.
In another report, in the journal Proceedings of the National Academy of Sciences, a pair of Israeli scientists found that the more dad cares for the kids, the more his brain looks and behaves like that of a mother engaged in the everyday care of a child.
Women produce boatloads of oxytocin after birth. But the scientists found increased levels of the hormone associated with nurturing, trust and affection in fathers and gay parents as they spent time nurturing their children.
And on MRIs scientists found the same neural paths firing in men and women when they watched videos of themselves with their children or other parents with children.
It makes sense that evolution would mitigate men and make them more amenable to family life. Women need help and support in caring for an offspring that is so helpless for so many years.
Though it might not seem like it in harried, two-earner households, fathers and mothers are actually spending more time with their children today than they were in the 1970s. And though women continue to do the lioness' share of child care, the ratio is now 2-1 where it used to be 4-1, said Mr. Wilcox, who also heads The Marriage Project.
"Fatherhood can be transformative for men," he said. "Especially married fatherhood and the day-in, day-out interaction with their spouse and children.
"It primes men to be better caretakers and to be less aggressive." A good kind of father to have.
And yes. A father that is more like us mothers.
Susan Reimer's column appears on Mondays and Thursdays. She can be reached at email@example.com and @SusanReimer on Twitter.com.To respond to this commentary, send an email to firstname.lastname@example.org. Please include your name and contact information.