* Archaeological evidence: Archaeological excavations at Harappan sites have uncovered Sumerian artifacts, such as cylinder seals and pottery. Similarly, Sumerian sites have yielded Harappan artifacts, such as beads and jewelry.
* Literary evidence: Sumerian texts mention trade with a people called the "Meluhha," who are believed to have been the Harappans. These texts describe the Meluhha as a rich and powerful civilization that traded with the Sumerians for goods such as gold, silver, and lapis lazuli.
* Linguistic evidence: There are some similarities between the Sumerian and Harappan languages, which suggests that the two civilizations may have had contact with each other.
The trade between the Sumerians and the Harappans was likely facilitated by the fact that both civilizations were located in river valleys. The Sumerians lived in the Tigris-Euphrates River valley, while the Harappans lived in the Indus River valley. These rivers provided a convenient means of transportation for goods and people.
The trade between the Sumerians and the Harappans was mutually beneficial. The Sumerians gained access to valuable resources, such as gold, silver, and lapis lazuli. In exchange, the Harappans gained access to Sumerian technology and culture. This trade helped to spread civilization and technology throughout the ancient world.