This reminded me of a theory I've been developing, I don't know if others have had it or have it, however an emergent behaviour that I've had some inklings may be true for humans relating to how old the parents are when having children. If having children at an older age (whether older age of male, female, or both) it could mean that resources and society are more stable - and perhaps another factor that there's more time to spend with, raise the children - giving them more guidance and having more nuanced knowledge to pass down, and so evolution may have selected for successful births at an older age toward creating children with different characteristics, behaviour, abilities.