Agriculture (Civ5)/Civilopedia

Agriculture is the production of plants and animals, most notably for food, but also for clothing, shelter, medicine, recreation, and other diverse uses. Crop cultivation probably developed independently in numerous places. The earliest evidence of agriculture thus far discovered dates back to the end of the last ice age, approximately 11,000 years ago. Interestingly, it appears that agriculture was not invented by starving hunter-gatherers desperately seeking new sources of sustenance; instead, evidence suggests that the earliest agriculturalists were successful and wealthy hunter-gatherers who probably had plenty of food already on hand. This makes some sense: people with a surplus of food can afford to experiment on new technologies, while those who are hungry are going to expend all of their energy on tried and true methods of gaining sustenance.
In its infancy, agriculture was a slow, cyclical process. Seeds were sown in the spring, the fields were tended and watered until the crops were ready to be harvested, often many months later. Since very few places have climates suitable for year-round agricultural production, farmers had to be able to store food for the lean winter months or they had to trade with those who could gather food year-round from hunting, fishing, and so forth. Farmers have always been at the mercy of nature and the weather: if it didn't rain one year or pests ate the crop, a family might simply starve.
Modern agriculture (or "agribusiness") is a complicated and exacting science of genetic manipulation, advanced fertilizer and insecticides, and computerized irrigation systems and robotic harvesters. Advances in the technology have greatly increased the output of food from a given acre of soil, so much so that some countries - including the United States - occasionally suffer not from famine, but from a glut of food, resulting in chronic obesity in their citizenry and prices so cheap as to threaten the livelihood of the very farmers who are growing all the food.