CLIMATE TWIST TO INDUS MYSTERY
BY G.S. MUDUR  
http://www.telegraphindia.com/

Scientists exploring a dry lake bed in the Thar desert have discovered geological evidence that challenges current theories linking the rise and mysterious collapse of the Indus valley civilisation to changes in climate.

Archaeologists have suggested in the past that the Indus valley civilisation came up 4,500 years ago during a period of abundant rainfall — conducive to agriculture — and collapsed around 800 years later when rainfall declined.

Now a team of Indian, Israeli and US researchers have found that the Indus valley civilisation thrived in a region that has been dry and arid over the past 5,000 years. When the Indus valley inhabitants were building the first cities in the subcontinent, the climate was as dry as it is today.

 

The researchers from the Deccan College in Pune, the Physical Research Laboratory in Ahmedabad and their co-workers from Israel and the US have reported these findings in the current issue of the US journal Science. The lead author is Y. Enzel from the Institute of Earth Sciences, Jerusalem.

Assuming that rainfall patterns would be reflected in the rise and fall of water levels in ancient lakes, the researchers dug three-metre trenches into the dry Lunkaransar lake, nestled among sand dunes 80 km north of Bikaner.

"The lake had dried up several hundred years before the Indus valley civilisation arose," Deccan College archaeologist and team member Sheila Mishra said. "Our findings suggest that the rise of the Indus culture did not coincide with improved rainfall," she said.

 

Historians had also suggested that the fall of the Indus culture could be related to a decline in rainfall and increasing aridity. The new study, however, does not support such a connection because the Lunkaransar lake had dried up more than 1,500 years before the Indus civilisation vanished.

 

The Indus civilisation flourished along rivers in a region with semi-arid climatic conditions similar to those at present, the researchers said in Science. The new findings thus challenge the climate-culture hypothesis for northwestern India and Pakistan.

The study indicates that the lake was shallow until 6,300 years ago when water levels rose abruptly. They remained high during a particularly wet phase that lasted around 1,500 years until the lake dried out around 4,800 years ago.

The research team also unearthed ancient ceramic pottery and charcoal remains — dated to be 4,250 years old — from the dry lake bed. This is an indication that humans had begun to live on the lake bed after it had dried up.

"The ceramic samples we found were not enough to identify their makers," Mishra said. But from the dating analysis, it seems that they were members of a pre-Harappan culture. "In the past, ceramic evidence from Rajasthan has suggested a diversity of pre-Harappan cultures," she said.

 

The Lunkaransar lake today is a small dry basin surrounded by sand dunes on the northeastern fringes of the Thar desert. It is mined for gypsum, but fills up with water for a few weeks during years of heavy monsoon rains.

The researchers say something other than the monsoon must have contributed t o the high water levels in the Lunkaransar lake during the 1,500-year wet phase that predated the Indus civilisation. They speculate that more winter rainfall than what occurs today may have been responsible. Desert regions serve as peepholes into past climates. A change in rainfall patterns can lead to rapid drying up of lakes and streams and changing water levels of the past can be analysed by studying underground soil samples.

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