Agriculture is the science and practice of cultivating of land, producing crops, and raising animals. It also refers to many associated processes or enterprises, such as food processing. No one knows precisely when humans first started a sustained, systematic practice of agriculture, but evidence has shown signs of agriculture in the Middle East and Mexico that date back to approximately 7000 BC. Some of the earliest cultivated crops included emmer wheat, wild barley, pumpkin, peas, and beans. The presence of larger scale, systematic cultivation often preceded or accompanied the rise of villages and cities and the formation of organized civilization.