G force

Go, daddy

Peter Gray plumbs the evolutionary history and health effects of fatherhood

Harvard-trained Peter B. Gray, an associate professor of anthropology at the University of Nevada-Las Vegas. Harvard-trained Peter B. Gray, an associate professor of anthropology at the University of Nevada-Las Vegas.
By Elizabeth Cooney
Globe Correspondent / June 14, 2010

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Harvard-trained Peter B. Gray, an associate professor of anthropology at the University of Nevada-Las Vegas, has written a new book with Kermyt G. Anderson titled “Fatherhood: Evolution and Human Paternal Behavior.’’

Q. How does fatherhood affect men’s health?

A. The data are mixed. New data have come out on postpartum depression in men. Men probably lose some degree of emotional support from their partner as a child enters the picture.

Q. What else might be going on?

A. How is sleep impacted by fatherhood? How does diet change with fatherhood? If you live in a subsistence society, you’re better off if you can put extra calories on your frame. . . . In the United States today, if you become more sedentary and you eat more, then you’re going to fatten up.

Q. Are men’s hormones affected, too, when a baby is born?

A. The most consistently observed hormonal correlate of fatherhood is lower testosterone levels in men. This could be picking up the behavioral transition men undergo as fathers as they move away from some degree of investment in courting women, seeking new mates, competing with other males, and begin to settle into a more family-oriented outlook, including spending time directly with a young child.

Q. You also talk about today’s hunter-gatherer societies. How are they like modern families?

A. There is a lot of variation in how much time men spend with their kids around the world. Those extremes include Aka men, guys in the Central African Republic who are probably as invested a group of fathers as ever found. Hunter-gatherers as a whole tend to [have] relatively socially monogamous marriages. Men are spending quite a bit of time around their kids, sleeping around their kids . . . like men in the US who might be attending prenatal classes with their partners and spending lots of time with their young children. Put it together and you may have some of the most intensive fathers ever in hunter-gatherers as well as in some niches in current society.

Q. Does all that attention make these men good fathers?

A. There is no one-size-fits-all fatherhood suit. Imagine you grew up in a small-scale warlike community where your value as a male includes deterring enemies from killing you, your wife and kids, and other members of your community. The expectation of you as a father may be related to forming a strong alliance with other men that helps in protection but that may not go hand in hand with much emotional intimacy or time spent with your kids.

Q. That sounds like “Mad Men.’’

A. I love that show. One thing presented in a show like “Mad Men’’ that was also a common family pattern in the baby-boom era in the US is this sexual division of labor. Women were at home and didn’t work. That does not apply well to an evolutionary backdrop. Among hunter-gatherers women and men are both working but in ways compatible with having young kids.

Interview was edited and condensed.

Elizabeth Cooney can be reached at