[lukifer]

The current conventional wisdom is that the birth rate is slowing in the industrialized world, and so overpopulation is no longer a serious concern. While this is the current demographic trend, I feel that such an assessment is short-sighted.

Natural selection (and common sense) tells us that individuals and cultures who value large families (Mormons, Catholics, etc.) will gradually out-populate those which do not. And as people who desire many children begin to make up a larger proportion of the population, it seems likely that overpopulation could resume its exponential trajectory.

[afterburner]

Yet the culture of those "large family" groups will probably change if they start to dominate, putting less emphasis on large families. The societal impetus to having a large family could come from an insecurity about your cultural block (not the individual impetus mind you, which can sometimes be more important, eg. kids to take care of you in old age or extra kids to overcome infant death). That clan insecurity starts to disappear when you start to become the majority in whatever context you feel is appropriate to consider.