In modern life, hedonism and low fertility is a default and it requires some special meaning to rise past that. For most, that meaning is religion.
(Before birth control of course, hedonists were leaving bastards everywhere.)
One of the consequences of modern contraception is the historically unprecedented decoupling of fornication and procreation. More of the former no longer means more of the latter. To the contrary, there is an inverse correlation between notch count and fertility (once the number of partners reaches one, of course!), a trend that is likely accelerating, not attenuating.
The following table shows the mean number of children men and women have had by the total lifetime number of sexual partners of the opposite sex they’ve had since turning eighteen. All respondents are at least 40 years of age. To avoid racial confounding, only non-Hispanic whites are included. For contemporary relevance, all responses are from 2000 onward (N = 6,999):
The repercussions of this decoupling are being played out now, the ultimate ramifications yet uncertain.
This probably plays some role in the relative prudishness of Zs and millennials, generational cohorts who are less sexually active and less recklessly promiscuous than Xers and baby boomers were at the same times in their lives.
From the middle of the 20th century onward, Western societies have experienced something novel for to humanity up to this point–men and women with fewer sexual partners having more children than men and women who have more of them. The Golden Horde or the House of Saud the contemporary Occident most certainly is not (yet). This isn’t the whole story, but it must be part.
GSS variables used: NUMMEN(1-989), NUMWOMEN(1-989), SEX, RACECEN1(1), HISPANIC(1), CHILDS, AGE(40-89)