Friday, April 23, 2010

Indus Valley east theory challenged



New Delhi, April 5: A study of hundreds of ancient Indus Valley civilisation sites has revealed previously unsuspected patterns of growth and decline that challenge a long-standing idea of a solely eastward-moving wave of Indus urbanisation.

Researchers at the Institute of Mathematical Sciences (IMS), Chennai, combined data from archaeology, radiocarbon dating, and river flows to study how settlements around the Indus Valley region had evolved from around 7000 BC till 1000 BC.

Their analysis of 1,874 Indus region settlements has shown that the Indus urbanisation had three epicentres — Mehrgarh in present-day Baluchistan, Gujarat, and sites along an ancient river called the Ghaggar-Hakra in Haryana and Punjab.

The findings, published in Current Science, a journal of the Indian Academy of Sciences, dispute suggestions by international researchers that farming and urbanisation in the region was driven by a “wave of advance” moving eastward. 

“We’re looking at large-scale patterns of how the Indus civilisation changed over time,” said Ronojoy Adhikari, a theoretical physicist at the IMS, who led a team that analysed geographic movements of Indus region settlements over hundreds of years.

“It’s like looking at something from a mountain-top — you get a different perspective than from examining archaeological sites,” Adhikari told The Telegraph. The analysis has also bolstered evidence for the idea that the civilisation did not abruptly collapse. 

The 7000 BC site at Mehrgarh, Baluchistan, provides the earliest evidence for wheat and barley farming on the Indian subcontinent. But the new study and earlier archaeological data suggest that the Indus civilisation may have picked up rice cultivation from eastern India. 

“This work provides new evidence to suggest that the Indus Valley civilisation had influences from the west and from the east — it was not a one-way west-to-east flow,” said Vasant Shinde, an archaeologist with Deccan College, Pune, who was not associated with the study. 

Shinde said archaeological excavations had pointed to rice cultivation near present-day Gorakhpur in around 7000 BC — the same period as wheat and barley farming in Mehrgarh. Remains of burnt rice from sites in Haryana and Rajasthan, dated to between 4000 BC and 3500 BC, and signs of rice cultivation in the Indus Valley region around 2500 BC suggest an east-to-west flow of rice cultivation, Shinde said.

The analysis by Adhikari and his colleagues shows a dense distribution of Indus Valley sites around 2500 BC which marks the beginning of the mature period of the civilisation — lasting about 600 years until about 1900 BC. 

The researchers believe it is during this period of high stability that the civilisation’s culture matured, leading to its script, the design of seals, and weights and measures. Adhikari said it was still unclear what kind of political organisation contributed to this uniformity in culture. 

The study shows a “catastrophic reduction” in the number of sites in the Ghaggar-Hakra region around 1900 BC. Over time, the Indus sites moved upstream, but they were smaller in size and appear to show a breakdown in large urbanisation. But the decline around Mehrgarh and Gujarat occurred at a much slower pace. 

Gujarat remained relatively unscathed during the Ghaggar-Hakra collapse, Adhikari said. Archaeologists say the findings are consistent with the idea that a slow decline of the Indus urbanisaton eventually gave way to the growth of settlements along the Gangetic plain. “I think the most significant aspect of this work is its demonstration of a new way to look at the remote past,” Shinde said.

Several international researchers, including Stanford University geneticist Luigi Cavalli-Sforza, have argued that farming originated about 10,000 years ago in the region of West Asia known as the Fertile Crescent and radiated into Europe and Asia.

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