> The species has spent a long time under selection pressure for "having more kids"
This needs to be carefully qualified. Infant mortality rates for the first 99% of human history were so shockingly, stupefyingly high, that a woman might only expect to have about three of her children survive to adulthood (and maternal mortality rates were also so high that a woman wouldn't expect to survive more childbirths than 5 or 6).
What this means is that the human population was only marginally above replacement for the majority of human history. Human population didn't explode until the medicinal revolution.
This article [1] claims that it's actually still quite higher than replacement, to make people around ancient Mediterranean have to resort to various kinds of birth control (be it violent or non violent). Medicinal revolution do lowers death rate significantly but I guess the reason why we haven't normalized late/late marriage pattern as birth control until recently is because of abundance of resource resulted by industrial and agricultural revolution.
1. https://acoup.blog/2025/08/08/collections-life-work-death-an...