It Wasn't Floods Or War: Scientists Crack 4,000-Year-Old Mystery About Why Indus Valley Civilisation Ended

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 triggered by series

of prolonged droughts that lasted for centuries, leading to desiccation of rivers and soils, and not due to a singular catastrophic event."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.

How cities collapsed one after another

Global climate simulations were used by the team to determine how rainfall and temperature changed between 5,000 years ago and 3,000 years ago in the area where the Indus Valley Civilization once thrived. The team analysed that as droughts worsened, populations shifted to 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."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.Four major drought events identified between 2425 and 1400 BCE, each lasting over 85 years. The third severe drought around 1733 BCE lasted 164 years, impacting the entire region.Overall temperature increased by 0.5°C, and rainfall decreased by 10%-20%, leading to significant hydrological changes.All these reasons led to the slow, gradual death of the Indus Valley Civilisation that flourished in parts of India and Pakistan 3,500 to 5,000 years ago. Hydroclimate dynamics and their impact on ancient civilisations, leave lessons for humanity today which is once again battling climate change challenges.