Agrarian Civilisation	A large, organized human society that relies on a large number of its members producing food through agriculture. May incorporate hundreds of thousands or even millions of people, and include cities together with their surrounding farmed countryside. Common features of agrarian civilizations include coerced tribute ("taxing"), specialized occupations, hierarchies, state religions, kings or queens, armies, systems of writing and numbers, and monumental architecture.
Agrarian Era	An era of human history, beginning roughly 10,000 years ago and lasting until the beginning of the modern era, when the production of food through agriculture was a central focus of many human societies, and a large number of people living in those societies worked the land.
Agrarian Surplus	The production of more crops and other food than immediately needed. One key to how a civilization develops specialized roles and a division of labour. The society that produces food in surplus can afford to have a class of people who don’t need to farm. These people can fulfil other duties in an increasingly complex society, including the roles of leaders, judges, bureaucrats, doctors, priests, artisans, slaves, or soldiers.
Agriculture	The cultivation of plant and animal species that are useful to humans for food or other purposes. A form of symbiosis, it generally results in genetic changes in the "domesticated" species over time. Agriculture can be vastly more productive than foraging technologies, though agricultural societies are also vulnerable to crop failure, disease, and other problems. Its appearance marks a fundamental transformation in human history.
Artificial Selection	The process by which humans breed plants or animals in order to cultivate certain desirable characteristics.
City	A large centre of population (usually with tens of thousands of people or more) with its own social and trade structure.
Civilisation	A human society having dense population, large public buildings, a central authority, and, often, a system of writing or other means of recording information.
Colonialism	The rule of one territory and its people by an occupying population from a different territory, often for economic gain.
Cuneiform	The world’s first known system of writing, written with reeds on wet clay in Mesopotamia (Sumer); the first written records date back a little more than 5,000 years.
Domestication	The process of taming an organism through generations of breeding to eliminate unwanted tendencies and cultivate desired ones.
Fertile Crescent	An area of fertile river valleys in Mesopotamia that contains the earliest evidence of agriculture.
Geography	The study of how physical features of the Earth and human interactions with the physical environment vary from place to place; often overlaps with geology, political science, economics, and many other disciplines.
Government	A person or group of people who maintain leadership and control over a city, state, or civilization.
History	The study of past events.
Ice Age	A cold period on Earth when much of the globe is covered by ice sheets and glaciers.
Irrigation	The control of the flow of water to support agriculture.
Mesopotamia	A region between the Tigris and Euphrates rivers that was the site of some of the earliest agrarian civilizations. Much of the region lies in modern-day Iraq.
Monumental Architecture	Large structures, such as pyramids, temples, public spaces, and large statues, that tend to appear wherever powerful leaders emerge; a feature of all agrarian civilizations.
Natufians	A group of people who lived in part of the Fertile Crescent some 12,000–15,000 years ago. Though they did not farm, they lived in settled villages, and their culture suggests some of the transitional stages between foraging and early forms of agriculture.
Pastoralism	A way of life similar to agricultural, but based primarily on the exploitation of domesticated animals rather than plants. To allow their domesticated animals to graze over large areas, pastoralists are generally nomadic.
Power	Power relations in human societies can usefully be analysed into two fundamental forms: Power from below (consensual or bottom-up power) is power granted by followers to a leader to ensure the successful achievement of group tasks. Power from above (coercive or top-down power) is power that depends on the ability of rulers to impose their will by force.
Sedentism	Living in one place for most of the year; rare in foraging societies but became widespread with the adoption of agriculture. Sedentism developed because agriculture made it possible to produce more resources in a given area and encouraged farmers to stay in one place to protect their crops.
State	A regionally organized society, capable of imposing its will by force, based on cities and their environments, and containing populations of tens of thousands and up to many millions of people.
Sumer	A region in Mesopotamia that was the site of one of the earliest agrarian civilizations.
Teosinte	A type of wild maize that is the ancestor of corn.
Uruk	A major city that emerged in Sumer about 5,500 years ago; one of the first big cities to emerge in the world, and probably the largest city in the world at its height.
Village	A small, settled community of people.