Evidence of an ancient "lost river civilization" has been uncovered off the west coast of India, the country's minister for science and technology has announced. Local archaeologists claim the find could push back currently accepted dates of the emergence of the world's first cities.

Underwater archaeologists at the National Institute of Ocean Technology first detected signs of an ancient submerged settlement in the Gulf of Cambray, off Gujarat, in May 2001. They have now conducted further acoustic imaging surveys and have carbon dated one of the finds.

The acoustic imaging has identified a nine-kilometer-long stretch of what was once a river but is now 40 metres beneath the sea. The site is surrounded by evidence of extensive human settlement. Carved wood, pottery, beads, broken pieces of sculpture and human teeth have been retrieved from along the river banks, according to a report in the Indian Express newspaper. Carbon dating of one of the wooden samples has dated the site to around 7500 BC.

"The carbon dating of 7500 BC obtained for the wooden piece recovered from the site changes the earlier held view that the first cities appeared in the Sumer Valley [in Mesopotamia] around 3000 BC," said B Sasisekaran of India's National Science Academy.

Tom Higham of Oxford University's Radiocarbon Accelerator Unit says submerged wood is often well-preserved and should be relatively straightforward to carbon date. "I don't see how you could get it grossly wrong," he says. "In the past, it has been said that you shouldn't pin all your interpretations on a date from one sample. But that's not so true these days. And dating a sample that's between 5000 and 10,000 years old is pretty easy."

Critical examination
If confirmed, the find would also push back the date of India's earliest known civilization by 5000 years. The Harappan civilization has been dated to about 2500 BC. The newly identified site "looks like a Harappan-type civilization but dating way back to 7500 BC," said minister Murli Manohar Joshi.

However, he cautioned that a "more critical examination" of the finds must now be carried out.

Sharad Rajaguru, a former head of archeology at the Deccan College in Pune, said: "These collections represent an exciting breakthrough in offshore archeology. Further investigation of the area is important as this might throw light on the development of human civilization, besides having a bearing on Indian history."

Joshi said the government is now forming a group of archaeological experts from institutes around the country to investigate further.

NewScientist.com: http://www.newscientist.com/news/news.jsp?id=ns99991808