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20,000 years under the sea
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It’s mid-morning on an already blisteringly hot day in May, and the sea breeze blowing off Tybee Island is doing little to cool things down.

But archaeologist Wendy Weaver is focused on a different time -- a time when May days were much chillier here on the south Georgia coast. In her hands, Wendy holds the object of her study: a clear plastic tube filled with mud that hasn’t seen sunlight in close to 10,000 years.

Weaver is part of a small team of experts studying sediment samples from the late Pleistocene and early Holocene Epochs. At that time, much of the earth’s moisture was locked in the icy grip of glaciers further inland, meaning prehistoric humans may have walked on land that has since been swallowed up by the sea.

The archaeologists are studying the seafloor in the Tybee channel, looking for evidence of those early men and women.

Judy Wood, the lead U.S. Army Corps of Engineers archaeologist on the project, is using the drill barge Explorer as her base of operations. Today, the barge is anchored near the edge of the shipping channel leading into the Port of Savannah.

Lifting itself out of the water on sturdy steel legs, Explorer is rock-solid above the shifting waves. The barge’s crew uses a towering industrial drill to bore into the sediments forty feet below the surface of the salty water.

There geologists have found evidence of an earlier riverbed crossing the modern-day channel. Now they want to find out whether people walked, hunted, and camped on the ancient river’s banks.

"That’s where people tend to want to live," Wood explains, "is near water sources and rivers. What we’re looking at is terraces that were next to these old channels to see if there are Native American sites that are six to ten-thousand years old out here."

In recent years, archaeologists have discovered a spearhead and the fossilized bones of large land mammals even further offshore — at Gray’s Reef National Marine Sanctuary. No one knows for sure how the artifacts wound up beneath seventy feet of seawater.

It’s unlikely Wood’s team will find anything as large as animal bones or stone tools, but they could find microscopic clues about what might have happened here eons ago. When this area was dry land, grains of plant pollen washed down the ancient riverbed and became part of the sediment.

They’re presumably still here now, entombed in the mud. These tiny prehistoric survivors can tell scientists what the weather was like thousands of years before the first meteorologist was born.

"If you find a lot of fir and pine pollen, you would infer that it was probably cool and wet," Weaver says.

On the other hand, grass and oak pollen paints a picture of a warmer, dryer climate. Sudden changes in the type of pollen found in mud from the same time period can signal drastic changes in the earth’s climate.

The old mud could contain other tiny climatic clues as well, such as microscopic pieces of full-grown plants or animal remains.

The two-day seafloor sampling is actually part of a larger project aimed at predicting what will happen if the Corps deepens the Savannah River. Doing so would allow bigger ships to travel up the river to the port facilities, but some environmentalists fear it might also allow saltwater to penetrate the sandy bottom and leak into the freshwater aquifer below.

Millions of people count on the aquifer for drinking water. Since Explorer was already drilling in the area, archaeologists took advantage of the opportunity to probe for historic resources, too.

The samples removed from the seafloor during this phase of the operation have been shipped to the Antarctic Research Facility at Florida State University for cold storage until they can be carefully studied. It’s likely the briny muck will help scientists learn more about the climate in southern Georgia during the last ice age — adding precious data to a very small pool of evidence.

"We’ve got quite a few pollen records, but they’re fragmentary because there are higher erosion rates on land," Weaver says. "Marine samples have a longer and more continuous picture of what was happening."

The old mud could contain other tiny climatic clues as well, such as microscopic pieces of full-grown plants, or animal remains. The odds are against finding any solid evidence of ancient humans.

Palynologist (expert in fossilized pollen and spores) Fred Rich of Georgia Southern University says, "from a geological perspective, humans have just scratched around on the surface. We leave very thin and indelible evidence that we’ve been here."

Since early humans constantly roamed around in pursuit of game, the only traces of their presence tend to be things like stone tools, the bones of butchered animals, or the ashes of ancient campfires.

The chances of the Corps of Engineers team finding any such things, Rich says, are "miniscule, because the cores they’re taking are not that big."

If the team should strike archaeological gold and find solid evidence of ancient humans, a chain of events will be set in motion.

"The goal is to find if there are any early man sites where we’re going to be dredging," says Judy Wood. "If so, we’d treat them just like we would any shipwreck or historic site." That could mean rewriting the proposal for deepening the channel.

Anthropologists are already rewriting the story of early humans in the Americas. For years, conventional wisdom has held that the first Americans wandered across a land bridge from Asia roughly 13,000 years ago, following the migration of large land animals.

But a new school of thought argues people were around much earlier than previously thought. In sites along the east coast, scientists are digging up items that appear to be Stone Age artifacts, some dating back as far as 16,000 years.

According to a recent report in the International Herald Tribune, a dig near the Savannah River in upstate South Carolina has yielded thin slices of flint-like rock that could be the cast-off work of a prehistoric toolmaker.

Nearby, archaeologists found charcoal from a fire that may have been started by early humans. Based on the depths where these items were found, experts say they could be 25-30,000 years old.

Other such sites have been found in Pennsylvania, Virginia, and South America. The finds lend support to the controversial theory that some of the first Americans may have moved up the Savannah River and other east coast waterways hunting and fishing tens of thousands of years ago.

In addition to helping explain the past, the ancient pollen could also foretell the future. Geologist Clark Alexander of the Skidaway Institute of Oceanography says the core samples might throw light on future ice ages or global warming.

"Certainly these pollen studies will lend a lot to our understanding of what the vegetation was like here," Alexander explained. "The more we can learn about that, the better we can understand what changes might occur in our own climate."

The earth’s climate has changed drastically since the ancient pollen was deposited in the ancient riverbed. If we discern what the pollen tells us about how those changes took place, perhaps we can better predict when similar changes might come again.