A general precondition for the development of early civilizations was the upper classes' ability to ensure that farmers produced substantial agricultural surpluses and that most of these surpluses be at the disposal of a small ruling group. Because agricultural surpluses constituted the main form of wealth in early civilizations, this control resulted in marked economic inequality.

The early civilizations were all low-energy societies, human labour being the principal and often the only source of energy for agricultural production. Further, while the Yoruba employed a wide range of iron agricultural implements and the Mesopotamians increasingly used copper and bronze ones, farmers in the other early civilizations made all their agricultural implements of stone, bone, and wood. The complexity of tool technology was not correlated with the intensity of food production or with the densities of population supported in the various early civilizations. The main factors determining intensity of food production were the farming techniques employed and the amount of labour invested in producing crops. The general simplicity of agricultural technology meant that early civilizations were confined to areas that had light, easily worked soils.

Unexpected variation has been found amongst these societies, however, in environmental settings, population density, intensity of agriculture, and the geographical mobility of people. Some, such as Egypt and Mesopotamia, developed in river valleys located in zones of low rainfall, where all but the simplest agriculture depended on some form of irrigation.