How an ancient civilisation survived 1000 years of climate change

At its peak, the ancient Indus River Valley civilisation featured gridded streets, multi-storey brick homes, flush toilets and bustling shops. Its people traded gold, precious stones and items such as bronze carts along the region’s waterways. Others carved detailed human figurines and moulded clay toys. They grew wheat, barley and cotton, and crafted tools to bring water for crops from nearby rivers.

The valley, largely located in modern-day Pakistan and northwest India, hosted one of the most advanced societies at the time, along with Mesopotamia and ancient Egypt. And then – with little signs of fighting or power struggles – it mysteriously disappeared.

Today’s scientists have been trying to explain the puzzling downfall of Harappa, one of the valley’s largest cities, by looking at the environmental conditions. In a study published last week in the journal Communications Earth & Environment, an international team used paleoclimate data and computer models to re-create the climate during the civilisation’s existence between 3000 and 1000 BCE. They found four intense droughts reduced rainfall and dried up waterways and soils, which probably caused Harappan residents to relocate frequently.

“The most surprising finding is that the Harappan decline was driven not by a single catastrophic event, but by repeated, long, and intensifying river droughts lasting centuries,” said Hiren Solanki, lead author at the Indian Institute of Technology at Gandhinagar, India.