How did these seals let us know that they traded? Well, because we found them in Mesopotamia, not the Indus Valley. Plus, archaeologists have found stuff like bronze in the Indus Valley that is not native to the region. So what did they trade? Cotton cloth. Still such a fascinating export, incidentally, that it will be the subject of the 40th and final video in this very series. But here's the most amazing thing about the Indus Valley people.