To an infant, a mother's body is both life and food, nature and nurture. This isn't true of fatherhood. Biologically, a father is a one-minute parent. Indeed, a man can become a father and be the last to know, sometimes years after the fact. What's more, his biological contribution does not naturally dictate his sociological role.
Sociological fatherhood is a lot like being a designated driver.
Because of this more tenuous connection, fatherhood is universally problematic. All societies face the challenge of connecting biological and sociological fatherhood in some fashion in order to make sure children are protected and supported over time. Within living memory, of course, there was a single prevailing model of fatherhood in America. In it, a father was connected to his children by three ties. The first was blood, or its legal equivalent, adoption.