Between 10,000 BC and 1700, the world’s population grew roughly from four million to six hundred million, at a rate of 0.04 percent per year; during this period the average life expectancy was less than thirty years. The world’s population has since risen to eight billion and the average global life expectancy is seventy-three years.

Writing in the late eighteenth and early nineteenth centuries, the English economist Thomas Malthus took the near-stagnant model which has characterized the majority of human history as indicative of the constraints which demographic growth imposed on economic development. Famously, he argued that population growth increased demand for food and other goods which were themselves constrained by the ecological limits of the earth, such as the declining fertility of the soil and the limited supply of land.

Malthus’s ideas were, however, only true if one assumed that it was not possible to increase the productivity of the economic system. For much of human history this was certainty true. Social relations characterized by the coercive exploitation of peasant producers created few incentives for increasing productivity by means other than force. Even where laborsaving technology did exist, feudal lords with near-absolute control over the lives of their peasants had few incentives to employ it.