A breakthrough scientific study claims to have finally solved the centuries-old mystery behind the collapse of the Indus Valley civilisation. The new findings challenge long-standing theories, revealing that the fall of this ancient urban powerhouse was not sparked by one dramatic, catastrophic event, but likely unfolded gradually through a combination of slower environmental and societal shifts.
A study published in the journal Communications Earth & Environment by an international research team utilised paleoclimate data and computer modelling to analyse the climate from 3000 to 1000 BCE.
The findings highlighted that the downfall of Harappa, one of the most significant urban centres of the Indus Valley Civilisation, was not due to a singular catastrophic event, but rather a series of prolonged droughts that lasted for centuries, leading to desiccation of rivers and soils.
"Successive major droughts, each lasting longer than 85 years, were likely a key factor in the eventual fall of the Indus Valley Civilization," the scientific team wrote in a statement.
As droughts worsened, populations shifted areas where water sources still existed. However, one by one, cities across the region collapsed. A century-long drought that started about 3,500 years ago "coincides with widespread deurbanization and cultural abandonment of major [cities]," the team wrote in the paper.
Global climate simulations were used by the team, to determine how rainfall and temperature changed between 5,000 years ago to 3,000 years ago in the area where the Indus Valley Civilization once thrived.
"The consistent decline in rainfall from 5000 to 3000 years [ago] across all simulations ensures that features such as multi-century droughts, monsoon weakening, or winter rainfall shifts are real, persistent signals and not artifacts of a single model," study lead author Hiren Solanki, a doctoral student at the Indian Institute of Technology at Gandhinagar, told Live Science in an email.