When Lee Gettler got married six weeks ago, he didn’t realize that with the “I do” came a change in his testosterone levels. Gettler is the lead author of a new study from Northwestern University that links male behavior to hormone levels.

Researchers studied more than 600 men in the Philippines and found that those who became fathers saw a substantial drop in their testosterone. Gettler said the findings show that males, like their female counterparts, are hardwired to take care of their offspring.

“It’s not just mothers that have an innate, kind of biological orientation towards childcare, men have that ability, too. And so I think that this can really broaden our idea of men as fathers and what the traditional role fathers should be perhaps, or what it means to ‘be a man.’” he said.

Gettler said the findings don’t mean that only males with low levels of testosterone have the potential to be able fathers—on the contrary. He said the study means that men with high testosterone levels during their single days have the capability of being more sensitive fathers. The drop in the level comes after a male chooses to have a child, according to their findings. Gettler said a similar drop occurs when men are newly married, though according to their findings, the drop is not as significant as it is during fatherhood.

Like with any study, there are possible limitations to the findings. Gettler admits with fatherhood comes stress or sleep deprivation, and those factors may have had an affect on the mental state of the males who were tested. But he said the novel finding in this study is that male behavior can drive biological change.  

For those men who are concerned a new baby could lead to more feminine features, Gettler says don’t worry—lower hormone levels just mean new dads will find it easier to tap into their sensitive side.