Actually, constant pregnancy is likely NOT the original state in humans. As long as a woman is breastfeeding, her fertility is highly reduced, spreading children out naturally - and in many “primitive” societies that exist today, children are breastfed for a long time.
And no, women having as many children as they could WAS NEVER the idyll you think it is, because even with rampant child and maternity mortality, that was often more than they could care for. And it was not uncommon that poor families would sell their excess children into servitude (or marry off the girls very early… who would likely have too many children too early themselves… perpetuating the cicle of poverty...) and not unheard of that they would abandon them (remember Hänsel and Gretel?) or even outright killing them.
But of course, you don’t care about that. No, all you care about is uncritical, context-deprived, mindless obedience to ancient directives from a completely different society and having Others to blame fir the wreck that is your life instead of yourself and your cult.
Tl;Dr: Family planning good, Ryan Messano bad.