The Indus Valley civilisation may be even older than initially thought.
Based on radiocarbon ages from different trenches and levels, the settlement at Bhirrana has been inferred to be the oldest (>9 ka BP) in the Indian sub-continent. To check its validity we dated archaeological pottery from two cultural levels using optically stimulated luminescence (OSL) method and thus investigated the interrelationship between the cultural levels and climate change that occurred right at the settlement, a critical gap in information that exists in our present understanding of the Harappan civilization.
Archaeological studies had earlier suggested that the civilisation was centred around Harappa and Mohenjo-Daro in Pakistan, and Lothal, Dholavira, and Kalibangan in India, Sarkar explained. The researchers from India now say it was actually spread over a much larger part of India, alongside River Saraswati, which is believed to have disappeared some 4,000 years ago.
Researchers have also proposed a new theory for the decline of the civilisation, which was earlier believed to have been caused by climate change.
The new study argues that although shifting monsoon patterns played a role in the eventual decline of the civilisation, it had more to do with the change in cropping patterns and storage of grains.
Because these later crops generally have much lower yield, the organised large storage system of mature Harappan period was abandoned giving rise to smaller more individual household based crop processing and storage system and could act as catalyst for the de-urbanisation of the Harappan civilisation rather than an abrupt collapse