In some mammals, fathers have literally no contact with their offspring while mothers care for them for years (eg, bears). In others, the mother and father both remain as part of a pack, but the mother does all of the direct care and the father is doing hunting or protection. In some, the father may have a minimal role in early life but then become more involved later as their offspring learn to hunt or fight.
The social construct of both parents having equal and identical roles in parenting at all stages of child development is very new and very culturally unique to Western, industrialized and affluent societies. Across all primates and all evidence of pre-industrial humans, maternal and paternal roles were very different.