During the Bronze Age, around 5000 years ago, a civilization thrived in the Indus Valley, spanning a region that includes parts of modern-day Afghanistan, Pakistan and India. Archaeologists consider it, along with two other contemporaneous cultures emerging in Mesopotamia and Egypt, to be among the most significant early urban settlements. Of the three enclaves, however, the Indus Valley community was the only one to successfully develop away from a permanent water source. Mesopotamian and Egyptian cultures relied upon an abundance of fresh river water for agriculture, migration and the transportation of goods. It had been a longstanding presumption among archaeologists that ancient settlers were attracted to an area because of its river. Why, then, was the largest concentration of Indus Valley settlement located a considerable distance from either the Indus or Ganges-Yamuna river systems?
A team of earth scientists has produced new research that may provide an answer. Using satellite imaging and examining geological strata in the region, the scientists have ascertained that there was once a powerful river flowing directly through the Indus Valley settlements but it diverted from this course thousands of years earlier. As it did so, the river marked the landscape with a `scar'—called a paleochannel—and deposited a fine-grain and fertile sediment that may have enticed the Bronze Age settlers several centuries later. The team suggests that the incised paleochannel was ideal for urban development because it offered an arable environment free from the threat of damage or crop loss caused by river flooding. It is likely, therefore, that it was the absence of the river, not its presence, which prompted these Indus Valley settlements.