Variously thought to have grown out of agricultural surpluses and/or trading crossroads, cities have their roots in the Neolithic (agricultural) revolution of circa 10,000 BC. Beginning as camps, then villages, the first major cities which satisfy the generally agreed upon definition of a city as populous, literate, hierarchical and monumental, emerged in the river deltas of the Nile, the Tigris and Euphrates, the Indus, and the Huang He rivers.
The city's essential evolutionary benefit was to safely harbor and incubate large populations, freeing some of them from hunting, gathering and farming so they could in turn tend to the arts, sciences, theology, trade, politics and inevitably, war. Unable to move per se, the city's cost was that if it was to endure, it had to ensure a surplus, defend itself against attack and placate its citizens. Almost invariably, cities exhausted the soils they originally took root in. Consequently, cities have historically generated an ever-expanding agricultural frontier, causing tensions between peoples seeking the same resources. Simultaneously, cities have tended to increase the materialistic desire of their citizens resulting in further resource extraction and ecosystem depletion.
Defined by their walls, the prototypical city also manifested a philosophically and spiritually dualistic sense of culture inside the city and nature beyond; a conceptual framework only now dissolving as the city of the 21st century and its related infrastructure takes hold of the entire planet.
1. Evolution of Urbanization: pre-modern era
Meredith Reba, Femke Reitsma, & Karen C. Seto, "Spatializing 6,000 years of global urbanization from 3700 BC to AD 2000," Scientific Data 3, 160034. Data available through the Yale University Seto Lab: Urbanization & Global Change, "Historical Urban Population Growth Data," http://urban.yale.edu/data (accessed June 18, 2016). Data made available under the Creative Commons Attribution 4.0 International Licenses: https://creativecommons.org/licenses/by/4.0/legalcode.
Critical Ecosystem Partnership Fund, "The Biodiversity Hotspots," http://www.cepf.net/resources/hotspots/pages/default.aspx (accessed July 1, 2014). Data made available under the Creative Commons BY-SA 4.0 License: https://creativecommons.org/licenses/by-sa/4.0/legalcode.