I’d reply in depth but I’m hung up on your suggestion that there was any time anywhere where 100% of families were two parents and two to four kids.

Any data for that? No women dead in childbirth, no large numbers of children for social / economic / religious reasons, no married but waiting for kids, no variation whatsoever?

I’d be very surprised if you could find one time period for one society that was so uniform, let alone any evidence that this was somehow universal until recently.

You claim to value facts above all else, but this sure looks like a fabricated claim.