The main purpose of this paper is to propose the hypothesis that inequality was essential for the sustainability and ‘development’ of early agriculturally based societies that developed in Prehistory and Ancient History. This was so for varied reasons: there was a need for some members of societies - the dominant class also called the elite - to escape from the Malthusian trap. In most cases, agriculture produced a bigger economic surplus eventually. Managerial problems – such as the ones associated with storage, the division of labor, irrigation, trade –being part of the consequences of the Neolithic revolution, created pressures to develop more centralized political organizations, a process which led later to the formation of the early states. This process allowed the appearance of powerful local chiefs who changed the nature of their original communities with new forms of social organization, in which one individual and his enlarged family - transformed into a ruling elite - received the benefits of the labor of a large number of serfs belonging to less-favored communities in neighboring areas. Although the surplus appropriated by the elite was used in specific ways – consumption, investments and expenditures on armed forces - it increased the power and wealth of these societies, albeit a solution involving unequally distributed wealth. While this is not the only factor in the growing dominance of agriculturally based societies, it is one of main ones as is evidenced by considering six early civilizations resulting from the Neolithic revolution. This result involves an important modification of Malthus’ theory. However, inequality - though necessary - was not a sufficient condition for the sustainability and economic development of these early societies.