People had less children in history than you thought.
“Our model Egyptian woman, married at 17, experiences nine live births and four (or three, depending on when menopause arrives) miscarriages. With nine live births and a 55% child mortality rate, 4.05 of those children survive to adulthood. That implies a net reproductive rate (NRR, the number of daughters who reach adulthood born to each woman who reaches adulthood) of two, which implies a population that would grow very rapidly, indeed far more rapidly that our evidence allows or than peasant economies could support. Instead, as Bruce Frier notes, the observed population trends we see in antiquity, combined with our estimates of child mortality, implies five to six live births per woman, not nine, to get an NRR just barely over 1 instead of 2.”