Domestication, Agriculture, and the Rise of Civilizations
There has been little biological change in Homo sapiens over the past 40,000 years -- in fact, probably as far back as the beginning of our species over 100,000 years ago. But the amount of cultural change, especially in technology and subsistence (how food is obtained), has been remarkable. One of the key cultural developments is the domestication of plants and animals, and the growth of farming (agriculture). Dozens of staple crops are grown today in the temperate and tropical regions. Almost the entire world's population depends, however, on just four major crops--wheat, rice, corn, and potatoes. The growth of farming and care of herd animals (pastoralism) began one of the most remarkable changes in Earth's ecology. The change began just 10,000 years ago and has been very rapid. During this period, many of the plants and animals over large areas have come under human control. The overall number of plant and animal species has decreased, replaced by the few needed to support large human populations. In the areas dominated by people, the interaction among plants and animals is usually controlled by a single species, our own. These environments are very different from earlier ones, in which the food chain was much more complex and many different plants and animals interacted.
The transition to agriculture, starting around 10,000 years ago, took place in several regions of the world. By this time, the cool, ice-age landscapes of 18,000 years ago had given way to warmer, wetter environments. People adapted to these changes by making more intensive use of the landscape. At first they took advantage of a broad range of plants and animals within each region, but later focused on certain wild plants and animals. Among the plants they exploited were cereal grains in western Asia and maize (corn as one variety) in Central America. By carefully collecting plants and controlling wild herd animals, people could select desirable characteristics in the food species they favored. This process of selection, protection, and controlled breeding eventually created new forms of life (such as sheep, cattle, pigs, and new species of wheat, corn and other plants) and useful products (such as milk, hides, and wool). Agriculture greatly increased the food supply, which encouraged population growth and settlement. Seeds, tubers, and livestock could be stored for long periods, an impossible achievement for hunting-and-gathering people.
Effects of Food Production on Human Society
By creating a readily available supply of plant foods, meat and milk, people were given some long-term food security. In contrast, the foraging lifestyle of earlier human populations never provided them with a significant store of food. With increased food supplies, agricultural peoples could settle into villages and have more children. The new reliance on agriculture and change to settled village life also had some negative effects. The average diet became more susceptible to diseases brought on by a lack of certain nutrients. A settled lifestyle also increased contact among people and between people and their refuse and waste matter, both of which acted to increase the incidence and transmission of disease.
People responded to the increasing population density -- and a resulting overuse of farming and grazing lands -- in several ways. Some people moved to settle entirely new regions. Others devised ways of producing food in larger quantities and more quickly. The simplest way was to expand to new fields for planting and new pastures to support growing herds of livestock. Many populations also developed systems of irrigation and fertilization that allowed them to reuse cropland and to produce greater amounts of food on existing fields.
The rise of civilizations -- the large and complex types of societies in which most people live today -- developed along with surplus food production. People of high status eventually used food surpluses as a way to pay for labor and to create alliances among groups, often against other groups. In this way, large villages could grow into city-states (urban centers that governed themselves) and eventually empires covering vast territories. With surplus food production, many people could work exclusively in political, religious, or military positions; in artistic and various skilled vocations; or as menial laborers or subjugated as slaves. All civilizations developed on the basis of such hierarchical divisions of status and vocation.
The earliest civilization arose over 7,000 years ago in Sumer in what is now Iraq. Sumer grew powerful and prosperous by 5,000 years ago, when it centered on the city-state of Ur. The region containing Sumer, known as Mesopotamia, was the same area in which people had first domesticated animals and plants. Other centers of early civilizations included the Nile Valley of Northeast Africa, the Indus Valley of South Asia, the Yellow River Valley of East Asia, the valleys of Oaxaca and Mexico and the Yucatn region of Central America and the Andean South America.
With the rise of civilizations, human evolution entered a vastly different phase. Before this time, humans had lived in small, family-centered groups essentially exposed to and controlled by forces of nature. Only a few thousand years after the rise of the first civilizations, most people now live in societies of millions of unrelated people, all separated from the natural environment by houses, buildings, automobiles, and numerous other inventions and technologies. Culture will continue to evolve quickly and in unforeseen directions, and these changes will, in turn, influence the physical evolution of Homo sapiens and any other human species to come.