About 3000 BC, as people started to live in cities and the world got more crowded, they also started to want a way to mark their property so other people would know who it belonged to. People also wanted a way to know whether anyone had been messing with their stuff.
Maybe the first use of seals was when a woman wanted to send some sheep to her brother in another town. She sent a slave shepherd with the sheep. But how could her brother know whether the shepherd had lost (or stolen) some of the sheep? So she made a lot of little clay balls, one for each sheep. She put these clay balls inside a clay envelope, and she stamped her own mark on the envelope, and then she sent the ball to her brother with the shepherd. When the shepherd arrived, her brother could count the sheep, and count the balls. If there were as many sheep as there were clay balls, then the shepherd had done a good job.The shepherd couldn’t remove any of the balls without breaking the envelope and then he wouldn’t be able to make the woman’s mark on it, so her brother would know the shepherd had cheated.
The earliest seals are from West Asia, from Mesopotamia, around 3000 BC. They started out simple, but soon they got very complicated so that they would be hard to copy.
People kept on using seals for a long time – in fact, you still sometimes see people using them today. In the Middle Ages, once people had begun to write their important documents on paper or parchment, they used blobs of wax to seal their documents instead of clay, and pressed their seals into the wax to identify themselves. King John of England, for example, signed the Magna Carta in this way.
Near Eastern Seals, by Dominique Collon (1991). A good introduction for adults.
The Chinese Chop Pack, by Robin Tzannes (2003). About Chinese seals (called chops), and includes some real chops for you to use!