The Indus Valley Civilization presents a profound historiographical puzzle: we have hundreds of excavated sites, thousands of inscribed artifacts, and abundant material evidence for a sophisticated, urbanized society — and we can read almost none of the direct testimony it left behind.

Mohenjo-daro and Harappa at their peak housed tens of thousands of people with standardized weights and measures, a sophisticated drainage system not replicated in South Asia for millennia, and an apparent absence of monumental palaces or temples. The grid plan of the streets, the standardization of brick sizes across sites 1,000 km apart — these imply coordination, but no citadel, no royal burial, no military imagery.

The script appears on approximately 4,000 seals and tablets in an inventory of perhaps 400-600 signs. It has not been deciphered, and the decipherment attempts remain contested. Without decipherment, we're limited to material culture evidence and comparative inference.

Current evidence points to long-term climate change drying up the Ghaggar-Hakra river system as a major factor in the civilization's decline around 1900-1700 BC. The population appears to have dispersed rather than collapsed catastrophically.