"Agriculture, by overcoming the limitations inherent in the closed system of hunting/gathering, made possible the open-ended expansion of both the population and the means of feeding it. Once it had been adopted, there was no turning back. The more that a civilization farmed, the more it needed extra hands, and so large families were deliberately procreated, which in turn produced still more mouths to feed. Colin Tudge calls it a vicious spiral, Ronald Wright a progress trap."