Mesopotamia

Four early civilisations grew up on river plains:

"Why rivers?" Water for crops, fertile soil and easy transport.

Mesopotamia and the Indus–Sarasvatī lands are fairly close to each other, so they had strong trade. Egypt and China show little clear evidence of direct contact with the Harappans.

Mesopotamia is a Greek name meaning 'the land in between', between the Euphrates and Tigris rivers. Today it is mainly Iraq and Kuwait, with parts of Turkey and south-western Iran. The curved foothills of the Zagros and Taurus mountains are called the Fertile Crescent, because they are so good for farming.

Farming began here about 12,000 years ago, and copper arrived around 4500 BCE, improving farming, crafts and trade. Over the next 2,000 years, some big cities became city-states: a city with its own government that also ruled the land around it. Four civilisations followed one another: Sumerian, Akkadian, Assyrian, Babylonian.

1. The Sumerians built the earliest city-based civilisation, at Ur and other cities of Sumer (today's southern Iraq). They were the first to:

• build dams and canals for irrigation;
• use mud bricks and burnt bricks for houses and walls.

Each Sumerian city grew round a grand temple for its chief god: the ziggurat, a stepped tower like a pyramid with floors, the holy temple on top. It was also the city's treasury, so its walls had only one entrance. Farming, trade and transport were all tied to the temple, and only high priests and priestesses could enter it. That shows a clear social hierarchy (people ranked high and low).

Writing. Around 3200 BCE, the Sumerians were the first to write. Scribes pressed a wedge-shaped reed into damp clay tablets. The script is called cuneiform, from the Latin cuneus, 'wedge'. Scribes had high status, and by 3000 BCE many city-states used cuneiform, even though they spoke different languages. The tablets record myths, hymns, laws, schooling, and the work of potters, carpenters and farm workers.

Sumerian inventions you still use:

• the wheeled cart and the sailboat;
• maths for buildings and measuring fields;
• a number system based on 60: that is why an hour has 60 minutes, a minute 60 seconds, and a circle 360 degrees.

2. The Akkadians took over in 2334 BCE, from the city of Akkad. They spoke a different language but used the same cuneiform. They built the world's first dynastic empire. The tablets of their king Sargon mention trade with Dilmun (today's Bahrain), Magan (today's Oman) and Meluhha, which is usually identified with the Harappan civilisation. They traded semi-precious beads, ivory, timber, gold dust and probably copper. (The Epic of Gilgamesh, one of the earliest written stories, comes from Mesopotamia.)

3. The Assyrians of the city of Assur, in the north, took power around 2154 BCE and lasted until the early 1700s BCE.

4. The Babylonians rose in central Mesopotamia from 1900 BCE. Their greatest king, Hammurabi (from 1792 BCE), built a large empire and collected rules for civil and social life into the Code of Hammurabi, carved on a stone pillar (a stele). It became a model for many later legal systems.

"Why did Babylon fall?" By about 1400 BCE it had lost its power: repeated attacks by the Hittites (from Anatolia, modern Turkey), who had new technologies; damage to the environment and pressure on farmland; and problems inside the kingdom.