Science writer Emily Anthes was online at Washingtonpost.com on Thursday, June 14, to discuss the physical and hormonal changes new dads go through. An unedited transcript of the chat follows.
Emily Anthes: I think there are a couple of reasons, which I touched on in the piece. First, I think that for a long time, the findings were simply counter-intuitive. (I wouldn't have guessed that fathers' hormones changed at all while they were waiting for a child to be born.) Second, the changes aren't that obvious—we weren't likely to accidentally discover hormone changes in male hamsters, for instance, unless we actually went looking for them. Finally, I think there's something that still a little bit politically incorrect about studying fathers instead of directing all our resources at mothers. Mothers clearly bear much of the pregnancy burden, and it makes sense to study them. (Also, women are famously neglected in medical studies, and I think some researchers felt that pregnancy and child-rearing was one domain in which women could get most of the attention).
Washington: How long after birth do these changes persist?
Emily Anthes: One of the most interesting findings of the 2006 brain study was that fathers with older children didn't show the same brain enhancements. As offspring become more independent, the neuronal changes seem to reverse themselves.
New York: Hi Emily—great article. I saw that one of the hormones linked to parenting is cortisol, the stress hormone. Do you know if there's any research into whether being in a high-stress environment could impact parenting, or where one would find such research?
Emily Anthes: Interesting question. It is conceivable, I suppose, that living in a stressful environment could increase cortisol and therefore spur parent-child bonding as a side effect. I'd suspect, though, that living with high levels of stress has, on balance, more negative than positive effects on parenting.
The connection between cortisol and stress has been somewhat problematic for those researching parenting, though. Obviously, as parents approach the birth of their child, stress levels will increase, and so scientists have had to be careful to separate these two effects.
New York: Fascinating article! My question is, does this explain why Seth Rogen is so fat in "Knocked Up"?
Emily Anthes: Probably not. Remember, his character does note that Allison "is prettier" than he is on the first night they meet—before she's even pregnant.
New York: Any sense of what the signaling mechanism is? If it's just being near a pregnant female, wouldn't males who are not the father also be affected?
Emily Anthes: I don't know what the precise signaling mechanism is or if one's been definitively proposed. It is possible (even likely) that the hormones of others who are living or spending time with a pregnant woman would also be affected. It turns out that groups of people who live together influence each others' hormones in lots of ways--girls who live with adult men, such as fathers, for instance, have been shown to start menstruating later—that we're just beginning to understand.
New York: Do these physiological changes—both before and after the child is born—depend at all on whether the man is the biological father or has been cuckolded?
Emily Anthes: I've addressed some of the issues of biological vs. non-biological fathers above, but your mention of cuckolding is interesting. In certain mammals, it is common for males to kill infants of their own species. This behavior can be adaptive for men who aren't fathers but is obviously not adaptive if men kill their own offspring. Studies have shown though, that when a male's mate is pregnant, he becomes indiscriminately less aggressive toward all youngsters, whether or not they're his kin. This behavior keeps a male from inadvertantly attacking his own offspring, but also means that if his mate was actually impregnated by another male—either before or after he himself mated with her--he would show the same physiological changes and the same paternal behavior as if the offspring were his own.
Washington: Great article! I hope to read more of your stuff on Slate. Was this column inspired by your own experience with pregnancy and the pseudo-pregnancy of your mate?