For civilization to develop, the land must be fertile enough to support an expanding population. Not only did early populations need a soil rich in nutrients, but also water. Egypt and Mesopotamia (literally, "the land between rivers"), blessed with just such life-sustaining rivers, are sometimes referred to together as the Fertile Crescent.
The two rivers Mesopotamia lay between were the Tigris and the Euphrates. Sumer came to be the name of the southern area near where the Tigris and Euphrates emptied into the Persian Gulf. When the Sumerians arrived in about 4000 B.C. they found two groups of people, the one referred to by archaeologists as Ubaidians and the other, an unidentified Semitic people. In the next couple of centuries the Sumerians developed technology and trade, while they increased in population. By 3800 they were the dominant group in the area. At least a dozen city-states developed, including Ur (with a population of about 24,000), Uruk, Kish, and Lagash.
With the increase in trade the Sumerians needed to keep records. The Sumerians may have learned the rudiments of writing from their predecessors, but they enhanced it. Their counting marks, made on clay tablets, were wedge-shaped indentations known as cuneiform (from cuneus, meaning wedge). The Sumerians also developed monarchy, the wooden wheel to help draw their carts, the plough for agriculture, and the oar for their ships.
In time, another Semitic group, the Akkadians, migrated from the Arabian Peninsula to the area of the Sumerian city-states. The Sumerians gradually came under the political control of the Akkadians, while simultaneously the Akkadians adopted elements of Sumerian law, government, religion, literature, and writing.
