Cultural selection, learning on an abstract level, is a product of female sexual selection. It lies two levels down from natural selection, but still must past muster when it comes down to an individual's survival to procreation age. Ideas also die, and must compete for survival like a fashionable color or song in female sexual selection. So, just as there is a branching tree of species representing their relationships over time, there is a smaller branching tree of selective processes representing their relationships and how one selective process generates another. With each branching there is a more select group of species effected by the processes at issue.
Natural selection affects all.
Sexual selection, uterine selection and zygote selection affect many. Cultural selection affects very few, and only one species we are aware of uses an abstract language. What drives this dynamic is the immediate advantage any individual has if he or she can transcend the barrier that is random variation. This is what it is all about. The implications of these findings is that an individual is able to strike an optimal balance between inbreeding and outbreeding by learning about its immediate kin and mating with a member of the opposite sex that is slightly different from its immediate kin.