Between 3000 and 2000 BC the Indus civilization was a vast network of complex, organized cities with flourishing trade links to the world beyond, all apparently thriving. And then, around 1900 BC, it came to an end. The cities turned to mounds of earth, and even the memory of this, one of the great early urban cultures of the world, vanished. We can only hazard guesses as to why. The need for timber to fire the brick kilns of the huge building industry may have led to extensive deforestation and an environmental catastrophe. More importantly, climate change seems to have caused tributaries of the Indus to alter their course or to dry up completely.

Neil MacGregor, A History of the World in 1…, loc. 240