Experts say millets, rice, and tropical pulses were used in the pre-urban and urban phases of the ancient culture.

The Indus Valley Civilisation underwent a period of climate change about 4,000 years ago, say scientists who suggest that the ancient population in India used a variety of subsistence practices to cope with diverse environments.

Researchers from the University of Cambridge in the United Kingdom and Banaras Hindu University in Uttar Pradesh worked in northwest India between 2007 and 2014.

They studied the dynamics of adaptation and resilience in the face of a diverse and varied environmental context, using the case study of the Indus Civilisation (3000 BC—1300 BC). They looked at how Indus populations in north-west India interacted with their environment, and considered how that environment changed during periods of climate change.

Water is of the essence

“For most ancient complex societies, water was a critical factor, and the availability of water and the way that it was managed and used provide critical insight into human adaptation and the resilience of subsistence practices,” said lead author Cameron Petrie of Cambridge.

Most early complex societies developed in regions where the climatic parameters faced by ancient subsistence farmers were varied, but not especially diverse.

Researchers showed that this region was subject to climate change during the period when the Indus Civilisation was at its height (2500 BC—1900 BC), researchers said. The civilisation provides a unique opportunity to study how an ancient society coped with diverse and varied ecologies and change in environmental parameters.

The Indus Civilisation was situated close to a deep lake Kotla Dahar, which would have been primarily monsoonal.

The lake showed evidence for two dramatic decreases in monsoon rainfall and a progressive lowering of the lake level.

The second of these shows Kotla Dahar becoming ephemeral during 2200-2000 BC as a result of an abrupt weakening of the monsoon, which is visible in speleothem records in Oman and northeast India.

Climate and deurbanisation

The proximity of the Kotla Dahar record to the area occupied by Indus populations shows that climate must be formally considered as a contributing parameter in the process of Indus deurbanisation, at least in the context of the plains of northwest India.

It has long been hypothesised that there was variation in the subsistence practices used by Indus populations and this fits with the theme of coping with diverse environments.

“We argue that rather than being forced to intensify or diversify subsistence practices in response to climatic change, we have evidence for the use of millet, rice, and tropical pulses in the pre-urban and urban phases of the Indus Civilisation,” said Mr. Petrie.

“This evidence suggests that local Indus populations were already well adapted to living in varied and variable environmental conditions before the development of urban centres,” he said.

The study was published in the journal Current Anthropology.