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KITTED out with the latest scuba gear, peers through the murky water to the seabed below. It’s dark – Momber is 11 metres below the water’s surface and the black peat of the seabed absorbs what little light reaches the bottom. Then the tide turns, and as clearer water flows in from the open seas, the decaying remains of an ancient forest emerge from the gloom. Working quickly, he records details of the exposed material before the strengthening current forces him away from the site.

This is all in a day’s work for Momber, who is director of the Hampshire and Wight Trust for Maritime Archaeology in Southampton, UK. His job is to search for clues to a prehistoric world lost beneath the waves in the channel that separates the Isle of Wight from the south coast of England – to be precise, at a location 300 metres off the port of Yarmouth.

Momber’s work is just part of a growing trend for searching the deep for clues to our distant past. The field of underwater archaeology is perhaps best known for unearthing relics from more recent history, like Henry VIII’s ship the Mary Rose, yet the seabed is stuffed with clues to prehistory too – especially a murky period 11,500 years ago, at the end of the last ice age, when early Europeans were slowly changing from being nomadic hunter-gatherers into settled farmers.

Back then, sea levels were 50 metres lower than today, and the vast majority of early societies would have lived on fertile land by the coast. But as the ice sheets melted, millions of square kilometres of coastal territory would have been flooded. By 4000 BC, when the coastline had stabilised to roughly its current form, 40 per cent of prehistoric Europe was submerged – along with much of the evidence for their way of life.

“Anybody who was doing anything on the shore more than 6000 years ago was doing it below present sea levels,” says of the UK’s National Oceanography Centre in Southampton.

The result is that remains found on land today are not going to tell you much about these early societies. “If you leave out 40 per cent of the data, you’re going to make some serious mistakes,” says Flemming.

What’s more, finds from the sea floor are well preserved. Indeed they are often in better condition than similar discoveries on land, since the low-oxygen conditions in mud and peat sediments slow the decay of organic material. Underwater sites can therefore provide unparalleled insights into the lifestyles of our ancestors as the ice age ended. “Underwater archaeology can open the door to how societies evolved and developed,” says Momber.

Underwater goes mainstream

Despite the treasures on offer, however, widespread acceptance of prehistoric underwater archaeology has been a long time coming. Until recently, underwater digs were regarded as dangerous and expensive, with the evidence hard to find. “With that attitude, people just didn’t look under water,” says Flemming, a pioneer of marine archaeology.

Now the tide is turning. Chance finds made by recreational divers and fishermen have whetted the appetite, and systematic investigations around the Baltic, together with improved underwater imaging techniques, have identified the best sites to look for human remains (see “Rebuilding the prehistoric world”). The final turning point came in 2003, when a multinational conference on the prehistoric potential of the North Sea and an accompanying book highlighted the new possibilities. “This really lit the blue touchpaper,” says Flemming.

“It has taken some time for the scientific community to acknowledge how important this is – and is going to be,” says of the University of Edinburgh, UK, “but underwater research is just now becoming accepted in the mainstream of prehistoric archaeology.” , an archaeologist at Oxford Brookes University, UK, agrees: “This is the next big story in archaeology.”

According to mainland archaeology, tribes living at the beginning of the Mesolithic period were mobile hunter-gatherers, preying on deer and wild boar in the continental heartland of Europe. Over the following millennia, they began to concentrate on the newly formed coastlines of northern Europe, becoming dedicated fishermen in the process. Understanding this transition, and how people adapted to coastal life, is tricky because rising sea levels had submerged these coastal Mesolithic sites. “We’ve been missing virtually all of the relevant evidence,” says archaeologist of the University of York, UK.

So where to look? The Baltic Sea seemed a good bet. Its brackish waters are particularly low in oxygen, while bays created by the convoluted coastline proved to be perfect havens for archaeological material for thousands of years.

One of the first important discoveries was made back in the 1970s, when Danish researchers unearthed a spectacular prehistoric site named Tybrind Vig, 300 metres from the current Danish coastline. Inhabited between 7500 and 6000 years ago, Tybrind Vig yielded three exquisitely preserved canoes made from hollowed-out lime trees, up to 9 metres long and each equipped with a stone fireplace, as well as paddles, fish hooks and fish traps.

It looked as though at least some of the Baltic Mesolithic tribes were intimately acquainted with the sea, but whether that was representative of Mesolithic life further afield remained unclear, until recent systematic excavations.

For example, the Sinking Coasts project, or , has been undertaking rigorous excavations along the German coast for the past seven years. These have unearthed sophisticated wooden fish traps and weirs, as well as fish hooks made from deer bone and harpoons made from antlers. The remains of literally thousands of bones of butchered fish suggest the prehistoric diet here was largely cod, flatfish, eels and dogfish, and, later on, included seals, porpoises and perhaps even killer whales.

Futher evidence from SINCOS confirms that the shift to seafaring was accompanied by a transition from nomadic life to a more settled existence. Large dumps of shells – the remains of harvested oysters, limpets and scallops – point to prolonged occupation of sites, and evidence of hunting camps indicate that settlement here was at least seasonal. It is likely that the inhabitants lived in wooden huts, although the evidence so far has been sparse.

Momber’s work at the Bouldnor Cliff site, near Yarmouth, paints a similar picture of a settled seafaring existence. Dives in the 1980s revealed the remains of an ancient forest here, but the real lucky break came in the late 90s, when archaeologists discovered dozens of flint tools from early human occupation, unearthed by burrowing lobsters.

Continued work at Bouldnor Cliff has paid off. The site also yielded the remains of what is believed to be an ancient log boat, and earlier this year Momber’s team discovered a complex of intersecting timbers embedded in protective sediment, together with evidence of burnt wood, flint, pegs and string. Roughly 8150 years old, the timbers feature distinctive cut marks, a sure sign that they were worked by human hands. It looks as though the site was an area of specialised industrial activity, and possibly a waterside platform where boats could be assembled. If so, Bouldnor Cliff was home to one of Europe’s oldest boatyards, underscoring the advanced craftsmanship of the Mesolithic people. “It’s an absolute gem,” says Flemming.

So it seems Mesolithic humans were sophisticated seafarers, but this existence wasn’t to last. Over the next couple of thousand years, these tribes would face a second, equally monumental shift to farming, as Neolithic agricultural cultures spread from western Asia across Europe, finally reaching northern Europe and mainland Britain about 6000 years ago. The exact nature of this transition, though, is something of a mystery.

“One of the most important questions in prehistoric archaeology is how this transformation to early agriculture took place,” says Benjamin. “Did migrating Neolithic people replace Mesolithic communities? Did they interact and trade with each other? Did Mesolithic people adopt Neolithic practices and technologies from neighbouring regions?”

Going Neolithic bit by bit

Once again, underwater archaeological projects such as SINCOS provide some clues, if not neat answers. “It’s a very complicated picture,” says SINCOS team member Harald Lübke of the Centre for Baltic and Scandinavian Archaeology at Schleswig-Holstein State Museum in Germany. Genetic analyses have produced conflicting results, but the underwater archaeological record hints at periods of interaction.

“If incoming Neolithic groups simply replaced Mesolithic groups, then we’d expect to see a rapid change in technology, but this is not what we see,” says Lübke. Instead, it looks as if bit by bit, late Mesolithic groups assimilated distinctive Neolithic styles of pottery and flattened axes, as well as domesticated animals and cereals.

The remains of cattle bones suggest that domesticated animals may have been introduced to coastal Mesolithic life by 6000 years ago, though fish and seal remains from this time indicate that marine resources were still important. New types of pottery, imported from south-eastern Neolithic neighbours, also begin to make an appearance. “Between 7000 and 6000 years ago, these Mesolithic people adopted some elements of the Neolithic, such as new ceramics and perhaps imported cattle, but they didn’t immediately change their entire subsistence system,” says Lübke.

It was only later, when people on the Baltic coast came to rely heavily on domesticated animals such as sheep and goats, that yet more Neolithic tools, such as polished axes, make their way into the archaeological record. By 5500 years ago, it seems the transition was complete, and coastal sites became less important as they were abandoned in favour of early Neolithic farms.

These results from northern Europe are only the beginning of the story. Benjamin, for example, has been researching and compiling geographical, geological and archaeological data in the eastern Adriatic, where he hopes to find insights into the final stages of the transition from Mesolithic to Neolithic in this region. “After a lot of research and preparation, we’ve isolated a few areas where we think there should be prehistoric material under water,” he says. Others hope to investigate the coastline of North America to reveal how tribal peoples migrated across the continent 15,000 years ago.

The best finds may be yet to come, but there is no time to lose. Much of the submerged Mesolithic treasure which has remained undisturbed in sediment for thousands of years is disappearing, says Anders Fischer, an archaeologist with the Heritage Agency of Denmark in Copenhagen.

Construction, dredging and trawling along coastlines are one set of problems. Then there is pollution, which destroys the underwater vegetation that helps preserve archaeological sites by stabilising the sediment. These problems are well documented in the Baltic and may be just as crucial in coastal waters elsewhere, according to Anders.

“Pollution destroys underwater vegetation that helps preserve archaeological sites”

Limited efforts have been made to protect some sites, by covering them with protective sheets for example. But preventing erosion and damage to sites on a broad scale around Europe is going to prove extremely difficult, says Fischer. “If we don’t act soon, we’re going to lose an important part of this cultural heritage forever,” he says.