The important changes new dads face have nothing to do with strollers or car seats.
bonding with baby
Credit: Kaysh Shinn

In children's stores across the country, you can see businessmen, writers, and accountants learning to become fathers. You'll find them trying to fold baby strollers without painfully catching their fingertips or see them working out how to safely install car seats.

But these scenes are a trivial example of what happens to men when they become fathers. The really important changes are happening out of sight, as men's body chemistry undergoes radical shifts to prepare them to be more nurturing and to mute the competitive instincts. In fact, men who marry and have children experience a significant drop in testosterone, along with changes in other hormones, to prepare them for fatherhood. And here's a bonus: Those changes could be good for men's health. Because elevated testosterone can increase the risk of prostate cancer and is linked with higher cholesterol, dads involved with their children -- that is, men who often have lower testosterone -- have a reduced risk of illness and mortality. Additionally, many researchers believe that a drop in testosterone could encourage men to drop their fists, at least for a while, and develop skills that become more important when they become fathers, such as cooperation and a greater ability to nurture.

New research is beginning to shed more light on what happens to men during this transition. James K. Rilling, Ph.D., an anthropologist at Emory University in Atlanta, examined a group of fathers and found that testosterone was lowest in dads who devoted more resources to their children and highest in those who invested less into their children. And fathers who devoted more resources to their children often had smaller testicles.

Another study, in the Philippines, found that men's sleeping arrangements also had an impact on their testosterone levels. Researchers found that men who cosleep with their children had significantly lower testosterone compared with men whose children slept in a separate room. The researchers concluded that there is a trade-off between the efforts devoted to mating and to parenting. Some males choose to devote more effort to mating and less to child care; others choose the opposite course. Although Dr. Rilling's research hasn't proven that testosterone levels can predict what kind of father a man is going to be, it helps explain why some are men doting, caring fathers and some decide to abandon their children.

Paul Raeburn is the author of Do Fathers Matter? What Science Is Telling Us About the Parent We've Overlooked, published by Scientific American/FSG, 2014.

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