Men's Testosterone Drops After Fatherhood, Study Says

Women aren't the only ones biologically programmed to take care of kids. It turns out men are also hardwired to be fathers, says a new study out of Northwestern University.

As soon as men hit fatherhood, testosterone plummets. And it continues to drop the more he gets involved in childcare duties like feeding and changing diapers, reports The Telegraph.

But perhaps you might assume men with lower testosterone are more likely to settle down and have kids. But researchers say if anything the opposite is true. "On the contrary, the men who started with high testosterone were more likely to become fathers, but once they did, their testosterone went down substantially," said Lee Gettler, an anthropology doctorate who worked on the study.

Carol Worthman, an anthropologist at Emory University who also was not involved in the study, explained to the New York Times this is part of a guy being invested in a relationship. "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," Worthman concluded.

The final surprise out of the report? Hormones don't just affect behavior, but men's behavior can affect hormonal changes. And one ultimate shocking finding: Women were meant to have child care help.

Of course, research linking relationships, behavior and hormones is nothing new. Women are said to have better memory if they take the pill. Whereas as a Harvard study as far back as 2003 found that the more time men spend in relationships, particularly marriage, they are more likely to have lower testosterone.