The Sumerians were among the earliest civilizations, emerging in Mesopotamia (modern day Iraq) around 3500 BCE. They developed new agricultural techniques like irrigation and animal domestication, leading to food surpluses and population growth. As populations grew, cities and social hierarchies developed, with different classes of rulers, merchants, artisans, farmers, and slaves. The Sumerians established the first cities and systems of government, law, and organized religion, making them among the first true civilizations.