Seals, script, weights, authority and the end

Seals. When goods were sent, the bag was tied with rope, the knot covered with wet clay, and a seal pressed on it. If the clay seal was unbroken when the bag arrived, the goods had not been tampered with; the sealing also showed the sender.

Script. The Harappan script has between 375 and 400 signs. It was written from right to left, and the longest inscription has only about 26 signs. It is not alphabetical (it has too many signs for that), and it remains undeciphered.

Weights. Exchanges were regulated by precise weights, usually made of a stone called chert, cube-shaped and without markings. Smaller weights followed a binary system (1, 2, 4, 8, 16...), larger ones a decimal system.

Authority. The uniformity of Harappan artefacts (pots, seals, weights, bricks) and the organised labour behind the cities suggest some authority. Was it a palace? We have found none clearly. Archaeologists hold three views: there were no rulers; there were several rulers; or there was one state.

The end. By about 1800 BCE, most Mature sites in regions like Cholistan were abandoned, while people moved into new settlements in Gujarat, Haryana and western Uttar Pradesh. Seals, the script, distinctive weights and long-distance trade vanished, and simpler rural settlements took their place. Whatever the cause (climate change, floods, deforestation, rivers drying up), a unifying element, perhaps the Harappan state, had come to an end.