That social structure is believed to "cause a muted physiological response in fathers" to any female marmoset, except for the love of his life, says Ziegler, lead author of a report on the research in a recent issue of the journal Hormones and Behavior. So in this case the physiology of the male suppresses the production of the hormones that could otherwise cause him a great deal of grief.
So for old dad, it's not a strength of character issue. The spigot, so to speak, has been turned off.
Does that make marmosets unique? Other studies have shown that various mammals, like pigs and bulls, respond as expected to a sexual stimulus. Within 30 minutes, their systems are charged and they've got all the hormones they need to take care of business. The same effect, by the way, has been shown among humans who are exposed to erotic materials.
But until now, there has been no reason to think that simply being a parent has any impact on the physiological processes needed to fire up the male. For marmosets, at least, it makes a difference indeed.
It will take a lot more research to see if anything similar to that happens to human males. Given the similarities between the social structures of humans and marmosets, it would not be surprising if being a dad at least makes some difference.
Snowdon says that would be good news.
"I'm tired of all men getting a bad rap for being supposedly promiscuous and irresponsible," he says. "I'm happy that we've finally found a species where, as parents, both females and males do the heavy lifting."
Incidentally, he's not a dad.
Lee Dye's column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.