By Alister Doyle

OSLO (Reuters) - Stone Age Britons imported wheat about 8,000 years ago in a surprising sign of sophistication for primitive hunter-gatherers long viewed as isolated from European agriculture, a study showed on Thursday.

British scientists found traces of wheat DNA in a Stone Age site off the south coast of England near the Isle of Wight, giving an unexpected sign of contact between ancient hunter-gatherers and farmers who eventually replaced them.

The wheat DNA was dated to 8,000 years ago, 2,000 years before Stone Age people in mainland Britain started growing cereals and 400 years before farming reached what is now northern Germany or France, they wrote in the journal Science.

"We were surprised to find wheat," co-author Robin Allaby of the University of Warwick told Reuters of finds at Bouldnor Cliff.

"This is a smoking gun of cultural interaction," between primitive hunter-gatherers in Britain and farmers in Europe, he said of the findings in the journal Science.

"It will upset archaeologists. The conventional view of Britain at the time was that it was cut off," he said. "We can only speculate how they got wheat -- it could have been trade, a gift or stolen."

The scientists also found DNA of oak, poplar and beech and of dogs or wolves, deer, grouse and auroch, a type of cow. There was no trace of wheat pollen in the samples, indicating that it was not grown locally.

The scientists found the DNA at what was apparently a pre-historic site for boat building. The sediments are now 11.5 metres (38 feet) below sea level.

Britain used to be connected by land to Europe during the Ice Age but melting icecaps pushed seas higher about 10,000 years ago. A land bridge may have lingered 8,000 years ago.

Farming reaching the Balkans about 8-9,000 years ago from the Middle East and eventually spread throughout Europe.

Greger Larson, an American archaeologist at Oxford University who was not involved in the study, praised the experts for extensive checks to ensure against mis-interpretation or contamination of DNA.

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The find of wheat "will make us re-evaluate the relationships between farmers and hunter-gatherers," he told Reuters.

He said there has been other signs of contacts, including bones of domesticated pigs in Germany in Stone Age hunter-gatherer settlements. "There are trade networks that pre-date agriculture," he said.

(Reporting By Alister Doyle)