You mention several good points, but, net, you miss it. The most serious place you get off the track is with your "If wanting more babies were a heritable biol

You mention several good points, but, net, you miss it. The most serious place you get off the track is with your "If wanting more babies were a heritable biological drive, we wouldn't see whole societies ignoring it immediately after it became economically rational to do so." No: There is "a heritable biological drive". But as I explained elsewhere on this thread, e.g., for the US population increase from 1800 to 1850, that "drive" long didn't play much role. Now with contraception, etc., that "drive" is crucial. Or, the lack of that drive, with contraception, etc., is now the reason for the fall in the birth rate. It's dirt simple: Now with contraception, more career opportunities for women, etc., women without that "drive" will be pulling their genes out of the gene pool. So, come back in a few generations and find what? Sure: Find what's left, find nearly all women who DO have just that "drive". You seem to doubt that the "drive" can exist and be from genes: Don't doubt! It's in the gene pool now: A significant fraction of women see the face of a baby and know right away, front and center, that they want BABIES. Then they go looking for a suitable husband. In particular they don't go looking for K&R on C. Look, it's even simpler: It's really easy for girls from 2 on to really love their dolls and like to play 'mommy'. Don't doubt that most of this is just in the genes.