Passage 1 Diving to the Depths of Human History
水下考古学 《新科学家》

[00:06]Diving to the depths of human history
[00:10]Equipped with the latest apparatus, Garry Momber peers
[00:13]through the water to the seabed below.
[00:16]It's dark - Momber is 11 metres below the water's surface.
[00:21]Then the tide turns, and as clearer water flows in from the open seas,
[00:27]the decaying remains of an ancient forest emerge from the gloom.
[00:32]Working quickly, he records details of the exposed material
[00:36]before the strengthening current forces him away from the site.
[00:40]This is all in a day's work for Momber, who is director of
[00:44]the Hampshire and Wight Trust for Maritime Archaeology in Southampton, UK.
[00:51]His job is to search for clues to a prehistoric world lost beneath the waves
[00:57]in the channel that separates the Isle of Wight from the south coast of England
[01:02]to be precise, at a location 300 metres off the port of Yarmouth.
[01:09]Momber's work is just part of a growing trend for
[01:12]searching the deep for clues to humans' distant past.
[01:16]The field of underwater archaeology is perhaps best known for
[01:21]unearthing relics from more recent history,
[01:24]like Henry VIII's ship the Mary Rose, yet the seabed is stuffed
[01:30]with clues to prehistory, too - especially an obscure period 11,500 years ago,
[01:37]at the end of the last ice age,
[01:40]when early Europeans were slowly changing from being nomadic hunter-gatherers
[01:45]into settled farmers.
[01:48]Back then, sea levels were 50 metres lower than today,
[01:53]and the vast majority of early societies
[01:56]would have lived on fertile land by the coast.
[01:59]But as the ice sheets melted, millions of square kilometres of
[02:04]coastal territory would have been flooded. By 4000 BC,
[02:09]when the coastline had stabilised to roughly its current form,
[02:13]40 per cent of prehistoric Europe was submerged along with much of
[02:18]the evidence for their way of life.
[02:21]"Anybody who was doing anything on the shore more than 6000 years ago
[02:26]was doing it below present sea levels," says Nic Flemming of
[02:30]the UK's National Oceanography Centre in Southampton.
[02:36]The result is that remains found on land today are not going to tell you much
[02:41]about these early societies. "If you leave out 40 per cent of the data,
[02:46]you're going to make some serious mistakes," says Flemming.
[02:51]What's more, finds from the sea floor are well preserved.
[02:55]Indeed they are often in better condition than similar discoveries on land,
[03:00]since the low-oxygen conditions in mud
[03:02]and sediments slow the decay of organic material.
[03:07]Underwater sites can therefore provide unparalleled insights
[03:11]into the lifestyles of humans' ancestors as the ice age ended.
[03:17]"Underwater archaeology can open the door to
[03:21]how societies evolved and developed," says Momber.
[03:26]Despite the treasures on offer, however,
[03:29]widespread acceptance of prehistoric underwater archaeology
[03:34]has been a long time coming. Until recently,
[03:38]underwater digs were regarded as dangerous and expensive,
[03:43]with the evidence hard to find. "With that attitude,
[03:47]people just didn't look under water," says Flemming,
[03:52]a pioneer of marine archaeology.
[03:55]Now the tide is turning. Chance finds made by recreational divers
[04:01]and fishermen have stimulated the appetite,
[04:05]and systematic investigations around the Baltic,
[04:09]together with improved underwater imaging techniques,
[04:13]have identified the best sites to look for human remains.
[04:18]The final turning point came in 2003,
[04:22]when a multinational conference on the prehistoric potential of
[04:26]the North Sea and an accompanying book highlighted the new possibilities.
[04:32]"It has taken some time for the scientific community to acknowledge
[04:36]how important this is - and is going to be,"
[04:40]says Jonathan Benjamin of the University of Edinburgh, UK,
[04:45]"but underwater research is just now
[04:47]becoming accepted in the mainstream of prehistoric archaeology."
[04:52]Jeffrey Rose, an archaeologist at Oxford Brookes University, UK,
[04:58]agrees: "This is the next big story in archaeology."
[05:04]According to mainland archaeology,
[05:06]tribes living at the beginning of the Mesolithic period
[05:10]were mobile hunter-gatherers, preying on deer
[05:13]and wild pig in the continental heartland of Europe.
[05:18]Over the following millennia, they began to concentrate on
[05:22]the newly formed coastlines of northern Europe,
[05:25]becoming dedicated fishermen in the process.
[05:29]Understanding this transition, and how people adapted to coastal life,
[05:34]is tricky because rising sea levels
[05:38]had submerged these coastal Mesolithic sites.
[05:43]"We've been missing virtually all of the relevant evidence,"
[05:47]says archaeologist Geoff Bailey of the University of York, UK.
[05:52]So where to look? The Baltic Sea seemed a good bet.
[05:57]Its salty waters are particularly low in oxygen,
[06:01]while bays created by the winding coastline proved to be perfect sites for
[06:06]archaeological material for thousands of years.
[06:10]One of the first important discoveries was made back in the 1970s,
[06:15]when Danish researchers unearthed a spectacular prehistoric site
[06:20]named Tybrind Vig, 300 metres from the current Danish coastline.
[06:26]Inhabited between 7500 and 6000 years ago,
[06:31]Tybrind Vig yielded three perfectly preserved canoes made from
[06:36]hollowed-out trees, up to 9 metres long
[06:39]and each equipped with a stone fireplace, as well as paddles,
[06:44]fish hooks and fish tools.
[06:47]It looked as though at least some of the Baltic Mesolithic tribes
[06:51]were intimately acquainted with the sea,
[06:54]but whether that was representative of Mesolithic life remained unclear
[06:59]until recent systematic excavations.
[07:03]For example, the Sinking Coasts project, or SINCOS,
[07:09]has been undertaking rigorous excavations along the German coast
[07:14]for the past seven years. These have unearthed sophisticated wooden fish tools,
[07:20]as well as fish hooks made from deer bone.
[07:24]The remains of thousands of fish bones suggest the prehistoric diet here
[07:30]was largely a variety of fishes.
[07:33]Futher evidence from SINCOS confirms
[07:38]that the shift to seafaring was accompanied by a transition
[07:42]from nomadic life to a more settled existence.
[07:47]Large dumps of shells point to prolonged occupation of sites,
[07:52]and evidence of hunting camps indicate that settlement here
[07:56]was at least seasonal. It is likely that the inhabitants lived in wooden huts,
[08:02]although the evidence so far has been sparse.
[08:05]Momber's work at the Bouldnor Cliff site, near Yarmouth,
[08:10]paints a similar picture of a settled seafaring existence.
[08:15]Dives in the 1980s revealed the remains of an ancient forest here,
[08:21]but the real lucky break came in the late 1990s,
[08:25]when archaeologists discovered dozens of flint tools
[08:28]from early human occupation.
[08:31]Continued work at Bouldnor Cliff has paid off.
[08:36]The site also yielded the remains of what is believed to be
[08:40]an ancient log boat, and earlier this year Momber's team discovered
[08:46]a complex of intersecting timbers in protective sediment,
[08:51]together with evidence of burnt wood, flint and string.
[08:56]Roughly 8150 years old, the timbers feature distinctive cut marks,
[09:02]a sure sign that they were worked by human hands.
[09:07]It looks as though the site was an area of specialised industrial activity,
[09:12]and possibly a waterside platform where boats could be assembled.
[09:17]If so, Bouldnor Cliff was home to one of Europe's oldest boatyards,
[09:22]underlining the advanced craftsmanship of the Mesolithic people.
[09:27]"It's an absolute treasure," says Flemming.
[09:30]So it seems Mesolithic humans were sophisticated sailors,
[09:34]but this existence wasn't to last. Over the next couple of thousand years,
[09:40]these tribes would face a second, equally monumental shift to farming,
[09:45]as Neolithic agricultural cultures spread from western Asia across Europe,
[09:51]finally reaching northern Europe and mainland Britain about 6000 years ago.
[09:57]The exact nature of this transition, though, is something of a mystery.
[10:02]"One of the most important questions in prehistoric archaeology
[10:06]is how this transformation to early agriculture took place," says Benjamin.
[10:13]"Did migrating Neolithic people replace Mesolithic communities
[10:18]Did they interact and trade with each other?
[10:20]Did Mesolithic people adopt Neolithic practices and technologies
[10:25]from neighbouring regions?"
[10:28]Underwater archaeology has huge potential, but it is a time-consuming
[10:33]and costly way to study the past. So resources need to be directed to
[10:39]the areas where researchers are most likely to find something valuable.
[10:45]Looking to the future, marine archaeologists still face a key challenge,
[10:50]namely to develop a global database for future research.