The advent of agriculture in Europe led to permanent settlements, which consequently led to a higher birth rate and thus to an increase in the population. This, in turn, enabled the storage of large quantities of food supplies, thus supporting non-productive social classes such as priests, bureaucrats, kings, soldiers, and artisans. The birth rate of nomadic hunter-gatherer groups could not exceed one birth every four years per family, and was limited by sexual abstinence, infanticide, and abortion. In a settled group, not limited by the need to transport children, they could have as many children as they could feed, thus reaching one birth every two years.
