A shift in society that triggers higher population growth is actually more likely than you might think due to evolution. Groups that have cultural norms that in

A shift in society that triggers higher population growth is actually more likely than you might think due to evolution. Groups that have cultural norms that increase fertility rates will steadily increase as a fraction of the population. As long as those groups can pass down their beliefs to their children with high probability, evolution will see those groups eventually become dominant. A good example of this would be the Amish population, which has very good retention and fertility rates leading to quite high population growth.