Archeologists dive for clues to early prehistoric settlement
From the summer Mercyhurst trip to the Gulf of Mexico off Florida with James Adovasio and C. Andrew Hemmings, searching for signs of early human activity: Researchers head for a dive site.
From the summer Mercyhurst trip to the Gulf of Mexico off Florida with James Adovasio and C. Andrew Hemmings, searching for signs of early human activity: Mr. Hemmings holds sample of chert, the hard stone from which prehistoric people made tools and weapons.
James Adovasio, director of the Mercyhurst Archaeological Institute.
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Onerous searches often are compared with finding needles in haystacks. But two Mercyhurst College archeologists are involved in a search dramatically more challenging.
That's because they've had to find the proverbial haystacks long before even thinking about finding the proverbial needles.
James Adovasio, director of the Mercyhurst Archaeological Institute, and C. Andrew Hemmings, a Mercyhurst research associate, plan next summer to dig for evidence of prehistoric humans about 130 feet underwater in the Gulf of Mexico sea bed.
It might sound odd, at least initially, that clues to human habitation of North America are submerged in the Gulf of Mexico.
But as far back as 22,000 years ago, a substantial portion of Earth's water was in the form of glacial ice atop the continents. Ice two miles thick, for example, covered current-day Erie, Dr. Adovasio said. Much shallower oceans meant coastlines extended hundreds of miles onto the continental shelves. So what once was dry coastline now is 130 to 160 feet underwater.
That means more than 9 million square miles of what used to be the coastlines of the world now are underwater, Dr. Adovasio said.
That left the research team a 350,000-square-kilometer area of the gulf to locate target spots, where they could dig through sediment and silt to turn up evidence of prehistoric humans.
Their finds, they said, could help answer questions that have lingered since 1492.
When did Native Americans first venture to the Americas? What route did they take? And once here, did they stick to the coast or immediately head inland?
Decades ago, Dr. Adovasio and his team unearthed human artifacts at the Meadowcroft Rockshelter in Jefferson Township, Washington County, that revealed human artifacts dating back 14,000 to 16,000 years. But Meadowcroft, widely considered the most ancient human site in North America, sits 380 miles from the Atlantic Ocean. Based on settlement patterns in Australia, people tend to live along coastlines, sometimes for millennia, before venturing inland.
That would suggest that humans had settled in North America long before they ventured inland to the Meadowcroft Rockshelter.
"In the grand scheme of things, the last chunk of land colonized by humans is the New World," Dr. Hemmings said. "The honest answer in my opinion is, we can't say within 5,000 years when people got here. We don't know."
Motivated to answer such questions, the Adovasio-Hemmings team landed a grant through the National Oceanic and Atmospheric Administration with matching grants from Mercyhurst and other universities participating in the research.
Using a side-scan sonar device and a sub-bottom profiler aboard the research vessel Weatherbird II, the team traced the ancient river bed of the Suwannee River from near Tampa, Fla., 100 miles into the gulf.
Next they pinpointed the ancient confluence of the Suwannee and St. Marks-Aucilla rivers, which represent a coveted haystack where they hope to find human artifacts. Such a confluence likely would lure prehistoric humans, especially if it had an outcrop of chert -- the hard stone from which prehistoric people made tools and weapons.
"The successful tracking of the St. Marks-Aucilla and Suwannee rivers between 50 and 150 kilometers respectively, represents what we believe to be the most extensive delineation of submerged prehistoric river systems ever done anywhere in the world," Dr. Adovasio said in a news release.
Dr. Hemmings' expertise is underwater archeology -- a difficult task considering high costs, sizable dangers and the limited time available deep underwater to do any digging.
Last summer, he and three other divers went down 130 feet to the target site, where they found chert. But with only nine minutes of air available, they had neither the time nor a dredge necessary to dig for artifacts. They will present their findings in upcoming presentations and papers with plans to reapply for NOAA funding to extend their project and dig for artifacts.
Any artifacts older than 16,000 years would alter perceptions about the earliest human history in North America.
"We found the haystacks," Dr. Hemmings said. "Now we have our hands on the needle cases.
"With a dredge and a few hours of digging, we have a good shot of finding artifacts," he said.
Excavation at the site, he said, could turn up leaves, shells, seeds, wood and cordage, bone, ivory and tools that early humans left behind. If so, the location could prove that humans lived in North America as many as 26,000 years ago -- or 10,000 years earlier than Meadowcroft.
Still, the Gulf of Mexico seems an unlikely location for researchers to solve land-based mysteries of prehistory.
"We are missing the first chapter of archeology if we are not looking underwater," Dr. Hemmings said. "There are good reasons specifically to be in this place."
First Published September 23, 2009 12:00 am