The major technologies that promoted the advancement of Mesopotamian civilization were related to the development of agriculture. Mesopotamian peoples independently developed irrigation, which allowed for the spread of farming away from river valleys. They also developed technology to control flooding of the Tigris and Euphrates rivers and their tributaries. They domesticated various cereals that grew wild in the area and bred them for maximum hardiness and nutrition. They also began to work with metal tools, becoming one of the world's first Bronze Age civilizations. These inventions enabled intensive, high-yield (by ancient standards) agriculture, which in turn enabled the development of a complex, sophisticated society that was responsible for major advances in writing, science, mathematics, medicine, politics, and law.