Contracepted acts radically flatten and shrink our perception of the sanctity of man-woman bodily union.
That has certainly been borne out by experience. a contraceptive culture has no concept of "sacredness" in respect to sex--- none at all. And such a culture is ever MORE abortion-minded. Contraception does not help matters. Contraception and abortion, historically, go up in tandem.
A perspective more fully elucidated here
Did you realize that such populations, with 1/4 the reproduction rate of everyone else, yet the same or even higher death rate, tend not to grow over geologic periods of time?
A tribe could only boost its population through the expedient of passing around the women to see who could get pregnant.
Typically a woman, or a man, facing this dilemma, will have 5 spouses over the course of the normal breeding age.
Charles Darwin was apparently unaware that ran in his family and then he ended up married to a first cousin ~ and half their kids ended up infertile (much to everyone's consternation).
I always take all of the standard arguments (for or against divorce, wife-swapping, contraception, and other sexual matters) and crank them through the logic of this condition.
Onan may well have run afoul of the pro scripts in a population with indeterminate infertility ~ which is why he was killed by a lightning bolt ~ which is a suggestion this is a really, really, really ancient story probably handed down by Ice Age hunter/gatherers who were probably all afflicted with the condition.
(God, of course, is the author of moral prescripts, but with Onan you are looking at a death penalty for behavior he probably didn't invent ~ and it's highly unlikely the Hebrews in Moses' camp were subjected to all that many death penalties for that particular sin ~ hence it's a moral lesson, not a current event).