As parents, we sometimes mistakenly assume that things were always this way. They weren't. The modern family is just that - modern - and all of our places in it are quite new. Unless we keep in mind how new our lives as parents are, and how unusual and ahistorical, we won't see that world we live in, as mothers and fathers, is still under construction. Modern childhood was invented less than seventy years ago - the length of a catnap, in historical terms.