I’ve been working through Gary Becker’s A Treatise on the Family: Enlarged Edition over the last couple of weeks. One interesting section included Becker’s thoughts on why people demand their own children, as opposed to being satisfied with the children of others.
[T]he demand for own children, the distinguishing characteristic of families, need not be postulated but can be derived.
Women producing children can use their own milk as food and can more readily take care of young children while pregnant than while working in the marketplace. Moreover, most women have been reluctant to commit so much time, effort, emotion, and risk to producing children without considerable control over rearing. Presumably the genetic similarity between parents and children further increases the demand for own children.
Own children are preferred also because of the value of information about children when investing in them. Information is more readily available about the intrinsic characteristics of own than adopted children, because parents and own children have half their genes in common and the health and some other characteristics of own children at birth and during infancy are directly observed. … This may also explain why orphaned children of siblings and other close relatives are more frequently adopted than are orphaned children of strangers (Goody, 1976), and even why adopted children are less valued as marriage partners.
Becker introduces biological considerations at several points of the book, but this explanation of the demand for children is one of the more awkward. It’s not hard to see what would happen to those who overcome this information asymmetry to allow them to efficiently raise children that are not their own.