Populations that stop reproducing is a problem that solves itself. Probably cultures and individuals that are more likely to desire babies will push forward.
unlikely. historically the most important cultures were a small minority of human population
That's a bold claim, can you unpack? Also, important for who?
the whole constellation of western cultures that dominated the world came from small populations.
Important for , let's say, technology, since technology gave them military advantage
Dominated the world for the tiniest sliver of human civilization. Asia is coming back strong again.
Nonsense. For 95% of recorded human history the Chinese and Indians were the richest and most productive civilizations and you can’t call those populations small. It’s like you’re living in your own narrative.