The first longitudinal study of testosterone levels in fathers has found that the longer a man has been a father--and the more involved with the daily care of his children he is--the lower his testosterone level drops.
The study measured testosterone levels in 21-year-old men before they became fathers, and then again 5 years later. Those who became fathers had more than double the drop in testosterone than non-fathers (all men experience a drop in testosterone as they age). And those men who spent more than three hours caring for their children each day had the lowest level of all.
The New York Times reports on the study, which was published in the journal Proceedings of the National Academy of Sciences:
"The real take-home message," said Peter Ellison, a professor of human evolutionary biology at Harvard who was not involved in the study, is that "male parental care is important. It's important enough that it's actually shaped the physiology of men."
"Unfortunately," Dr. Ellison added, "I think American males have been brainwashed" to believe lower testosterone means that "maybe you're a wimp, that it's because you're not really a man.
"My hope would be that this kind of research has an impact on the American male. It would make them realize that we're meant to be active fathers and participate in the care of our offspring."
The study, experts say, suggests that men's bodies evolved hormonal systems that helped them commit to their families once children were born. It also suggests that men's behavior can affect hormonal signals their bodies send, not just that hormones influence behavior. And, experts say, it underscores that mothers were meant to have child care help.
"This is part of the guy being invested in the marriage," said Carol Worthman, an anthropologist at Emory University who also was not involved in the study. Lower testosterone, she said, is the father's way of saying, " 'I'm here, I'm not looking around, I'm really toning things down so I can have good relationships.' What's great about this study is it lays it on the table that more is not always better. Faster, bigger, stronger — no, not always."
(image via: http://www.hfihouston.org)