I don't think this is an idea, I think the 2 parent system is biology and collective parenting is the "idea" built on top of it. Here's why: https://www.webmd

I don't think this is an idea, I think the 2 parent system is biology and collective parenting is the "idea" built on top of it. Here's why: https://www.webmd.com/parenting/baby/forming-a-bond-with-your-baby-why-it-isnt-always-immediate#1 https://www.webmd.com/parenting/baby/forming-a-bond-with-you... Biological bonding with baby is recorded to happen after 80% of births at first sight. The bonding is so strong that parents will literally lay down their lives to protect a child. I highly doubt that this type of bonding forms for people who aren't the biological parent of the baby. When choosing their own lives or the baby's life, most unrelated people will choose their own life. Therefore under "collective parenting" it is likely that the other "parents" function more as "caretakers" and are tertiary to the parents that formed the biological bond. Foster care is largely comprised of tertiary care that is missing the primary care of the nuclear biological mother and father. So foster care is essentially the same as collective parenting just without the actual biological parents. This is the causative factor and the essential missing link: Foster care doesn't have enough people who are willing to invest the same amount of blood, sweat and tears as actual biological parents. That is why I said such support services are unsustainable. People don't have enough energy, resources or will-power to spare for a stranger that is not their own biological progeny. You also need to consider the evolutionary logic behind this type of behavior. Does it make sense for a biological entity to maximize Darwinian fitness by caring for children that have less genetic relation to them? No. Obviously there will be an evolutionary imperative for parents to spend the most resources on the child that is most genetically related to them. The 2 parent system exists as a primary biological component rather than some "idea" because a child can only have 2 biological parents.