Scientists have demonstrated that an abrupt weakening of the summer monsoon affected northwest India 4100 years ago. The resulting drought coincided with the beginning of the decline of the metropolis-building Indus Civilisation, which spanned present-day Pakistan and India, suggesting that climate change could be why many of the major cities of the civilisation were abandoned.
Reported this week in the journal Geology, the research (by Professor David Hodell, from Cambridge’s Department of Earth Sciences, together with University of Cambridge archaeologist Dr Cameron Petrie and Gates scholar Dr Yama Dixit) involved the collection of snail shells preserved in the sediments of an ancient lake bed. By analysing the oxygen isotopes in the shells, the scientists were able to tell how much rain fell in the lake where the snails lived thousands of years ago.
The results shed light on a mystery surrounding why the major cities of the Indus Civilisation were abandoned. Climate change had been suggested as a possible reason for this transformation before but, until now, there has been no direct evidence for climate change in the region where Indus settlements were located.
For more information on this project see: http://www.cam.ac.uk/research/news/decline-of-bronze-age-megacities-linked-to-climate-change