What Mesopotamia needed
The river plains of southern Mesopotamia were fertile, producing barley, dates, wool and fish, but they lacked metal ores, building stone and good timber. These had to come from outside. This need drove a trade that stretched down the Gulf, using boats that carried goods between Mesopotamian cities and the lands of Dilmun, Magan and the Indus region. The voyages ordered by rulers are discussed in the article on Dilmun and Magan voyages, while this one concentrates on the trade itself.
Copper
The best-documented import was copper, which was needed to make tools, weapons and vessels. The main source in the third millennium BCE was Magan, generally identified with the Oman peninsula, where copper ore is plentiful and was worked in ancient times. Texts from Ur, especially of the early second millennium BCE, record shipments of copper by merchants sailing from Dilmun. The Gulf copper trade may have included smaller amounts from other areas, such as Iran, though the proportions are hard to measure.
A famous example is a set of clay tablets from Ur, dated to around 1750 BCE, relating to a merchant named Ea-nasir. They include a complaint from a customer about the quality of copper delivered. The tablets are often cited because they show an ordinary commercial dispute, though they should not be mistaken for a full picture of the trade.
Timber and stone
Mesopotamian builders needed wood for roofs, doors, boats and furniture. Timber came from regions in the north and east, and from the Gulf side, as imported woods and perhaps trees from areas beyond. Stone such as diorite, used for statues and vessels, is named in texts as coming from Magan, and the use of this stone for royal statues is documented in the inscriptions of Gudea of Lagash. Other materials included ivory, gold and shell.
The Indus connection
The Indus valley civilisation, in modern Pakistan and north-western India, flourished in the third and early second millennium BCE. Mesopotamian texts name Meluhha as a distant land that supplied exotic goods such as carnelian, lapis lazuli, ivory and certain woods. Many scholars identify Meluhha with the Indus region. Archaeological evidence supports a link: Indus seals and weights have been found in Mesopotamia and the Gulf, and carnelian beads of Indus style appear in the royal graves of Ur.
How goods travelled is less certain. Ships may have sailed directly between the Indus coast and the Gulf at times, but exchange may also have been handled by intermediaries at Dilmun and other ports. The mention of Meluhha in texts declines in the early second millennium BCE, which fits the decline of the Indus cities, though the causes of that change are debated.
Dilmun as a hub
Dilmun, centred on Bahrain, lay on the sea route between Mesopotamia and further east and south. It had access to fresh water from springs, an unusual advantage in the region, and it became a stopping point and market. Excavations at Bahrain have revealed a city, sometimes associated with the site of Qal’at al-Bahrain, and burial mounds on a large scale. Dilmun seals, with their own style, also show contact with both the Indus and Mesopotamia.
Dilmun was also idealised in Sumerian myth as a pure and bright land. The mythological image should be kept separate from the historical trading place, although the two may be linked in the minds of the people who wrote about it.
Merchants and records
Merchants in Mesopotamia, known by the Akkadian term tamkarum, operated within a system of temples, palaces and private firms. They could act as agents for institutions, and also trade on their own account. Texts record loans, partnerships and shipments, with silver used as a standard of value. Goods leaving Mesopotamia in exchange for imports included textiles, wool, barley, oil and silver. Because the evidence consists of clay tablets in the archives of cities like Ur and Lagash, it covers certain places and periods well and others hardly at all.
Ships
The vessels that carried the cargoes were probably varied. For rivers and marshes, there were reed boats and rafts, as discussed in the article on bitumen-sealed hulls. For the Gulf, texts imply larger ships, and some inscriptions suggest vessels of considerable carrying capacity, though the numbers in those texts are not reliable. Sailing in the Gulf would have been aided by winds that changed seasonally, and the wider rhythm of the monsoon trade winds shaped the Indian Ocean routes further east.
Decline and change
By the early second millennium BCE, the pattern was shifting. The Indus cities declined, Dilmun’s fortunes changed, and the Mesopotamian political landscape was reshaped. Later, in the first millennium BCE, the Gulf remained a place of trade, and the Persian Gulf and its pearl fishery became famous. The earliest story, though, is one of southern Mesopotamians reaching out to the shores of Oman and the Indus for the materials they could not produce, and it is among the first well-documented examples of long-distance maritime trade, a theme developed in the overview of ancient maritime commerce.