Secrets of the sea bed: Hunt for Stone Age site in North Sea

British and Belgian scientists are exploring the sea bed off Norfolk hoping to find evidence that Stone Age people lived there when it was still dry land.

In recent years, some trawler crews and researchers have found prehistoric animal bones and basic stone tools in North Sea sediment.

The team on the Belgian ship RV Belgica aims to map the Brown Bank area, a sand ridge about 30km (19 miles) long.

Mesolithic people are thought to have lived there in about 10,000-5,000BC.

"We suspect that the bank is on the edge of a large prehistoric lake, where you would expect settlements," said Prof Vince Gaffney, an archaeologist at the University of Bradford.

Despite the prehistoric finds from the North Sea bed, so far no Mesolithic settlement has been found in that vast area, which flooded after 6,000BC as the Ice Age glaciers retreated.

Eventually the British Isles were cut off from the continent.

When the coast of continental Europe reached as far north as Norway, at the end of the Ice Age, the sea level was about 120m (394ft) lower than today.

"Areas under the North Sea now would have been the best to live in during the Mesolithic [period] - prime real estate, because the coastlines then had fish, birds, fresh water. But it is terra incognita," Prof Gaffney said.

Brown Bank is about 100km (62 miles) from the Norfolk coast. It used to form part of a vast plain known as Doggerland.

For much of the Stone Age, before the Neolithic period, humans were nomadic hunter-gatherers.

But a Mesolithic settlement was discovered at Howick village, near the Northumberland coast - evidence that as long ago as 10,000BC some communities in Britain were no longer nomadic.

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Bradford archaeologists working with Prof Gaffney are aboard the oceanographic Belgian navy vessel with geologists from Belgium's Ghent University and the Flanders Marine Institute.

Scientists have already mapped more than 45,000sq km (17,375sq miles) of prehistoric landscape under the North Sea, an area larger than the Netherlands, Prof Gaffney said.

But Brown Bank awaits detailed mapping, and then sediment core sampling, to look for DNA and other evidence of prehistoric life.

"The area is so large that complete cultures could be out there," said Prof Gaffney, whose research project is called Lost Frontiers.

Ghent University geologist Dr David Garcia Moreno said the Belgica team could collect seabed samples and video sites of interest, but the goal at this stage was to understand the underwater topography in detail. They will use sonar and seismic equipment for that.

"We want to understand the evolution of rivers that traversed the southern North Sea.

"We think there was a Palaeolithic lake and a large river system all the way from north-west Germany south through Brown Bank to the Dover Strait," he said.

The research project, funded by the EU's European Research Council, is growing. It still has at least two years to run.

The Belgica is quite cheap to hire and they are already looking forward to their next expedition, Dr Garcia said.

But Doggerland is not the only undersea territory yet to be mapped and explored for prehistoric remains.

Prof Gaffney says the Bering Strait, off Alaska, and Indonesia's Sunda Strait are bigger. Who knows what prehistoric secrets lie there?