It seems that women aren’t the only ones affected by hormone fluctuations during child birth. Fatherhood, it seems, also comes with physiological changes.

A new study reveals that testosterone levels drop when men become fathers.

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.