This works in some interesting ways, starting with babies at six weeks of age, all of whom are born with the ability to relate differently to fathers than to mothers. Babies respond differently to their fathers' approach and touch, and the dads take the bait.
Right from the beginning it is clear to researchers that fathers (even when taking the primary responsibility for their children) do not mother, any more than mothers can ever father. Regular dads can comfort, feed, bathe, and nuture competently, given sufficient practice -- just as competently as mothers -- and the babies love it and thrive. The things that make fathering different from mothering have important and positive effects on kids over the course of their lives.