[gourabmi]

> Those societies in which few are willing to make the sacrifices necessary die out, and healthier societies take their place.

I think the comment means is that you can't have the cake and eat it too. Whether or not you want to make sacrifices in order to have kids, those choices will have consequences. Especially when sufficient number of people are doing it at the same time. The claim seems to be that the societies which prioritize sacrifices in order to raise children will outlives the ones that choose otherwise. Is that a good thing or a bad thing? Who knows.