I would like to inquire about another change which has occurred during this same time period. In fact, one usually grew up, got married, raised a family and dies within the same community. This made larger, multi-generation family networks, as well as other social networks stable through childhood. It also made one's play group stable throughout most of one's childhood, and relationships and responsibilities within one's social network clear. This changed drastically, starting in the 50s, up to the point where it is now unusual for any family to remain in a stable social network during the individuals' childhoods.
Families move, break up, changing schools and neighborhoods.
Family networks are reduced to occasional interactions through telephone and gifts and occasional holidays. One can have several sets of siblings which can change and other than one or two individuals, no stable relationships throughout childhood. Throughout the evolution of the species for sure, children grew up in stable social networks where bonding was permanent throughout life and social roles were well defined. I mean, there were always the same grandparents, parents and siblings and parents' siblings and so forth throughout childhood at least. Children were not emotionally dependent on only a one or two individuals, and there was a wide range of models and bonds.