Towns and cities are at the heart of human history. Even so, they are a relatively recent product of cultural evolution, and a radical transformation of the human habitat. As urbanisation gathers momentum around the world, the urban environment increasingly dominates the landscape of human social interactions and physical exposures. Life in cities presents a complex profile of gains and losses for human health.

Settled living first occurred in the Fertile Crescent of the Middle East as early agrarianism emerged. The consequences for infectious diseases and nutritional disorders have been explored in chapters 4 and 5. Equally importantly, the advent of settled agrarian living transformed humankind's social and economic relations, resulting particularly in the concept of ‘property’ – occupied farm-land, permanent dwellings, and a local market for exchanging surplus products. As rural settlements grew into larger villages, the increasing productivity of the land allowed the development of social stratification. As Charles Darwin remarked in his journal, commenting on the equality that he observed in the primitive inhabitants of Tierra del Fuego during his voyage on the Beagle: