The Indus civilization was the largest—but least known—of the first great urban cultures that also included Egypt and Mesopotamia.

Named for one of their largest cities, the Harappans relied on river floods to fuel their agricultural surpluses. Today, numerous remains of the Harappan settlements are located in a vast desert region far from any flowing river.

Liviu Giosan, Woods Hole Oceanographic Institution; Stefan Constantinescu, University of Bucharest; James P.M. Syvitski, University of Colorado

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