How do archaeologists known that the Harappan civilization traded?

The Harappan people used to trade with foreign lands traveling through seas. The seaports found in Harappan civilization state that they were not bound to their own territories. ... It was found that they also imported Jade from China and Cedarwood which were all traded through the rivers such as Sutlej, Ravi, and Indus.

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propioception;