Sinkhole Holds 12,000-Year-Old Clues to Early Americans

Willie Drye
for National Geographic News
February 18, 2009
Divers exploring a southern Florida sinkhole have uncovered clues to what life was like for some of America's first residents.

Led by University of Miami professor John Gifford, underwater archaeologists are exploring Little Salt Spring, 12 miles (19 kilometers) south of Sarasota.

Earlier this year, students working about 30 feet (9 meters) below the surface found the remains of a gourd that probably was used as a canteen by an ancient hunter about 8,000 or 9,000 years ago, according to Gifford.

Archaeologists have been recovering primitive relics from the spring since 1977, when divers found the remains of a large, now extinct tortoise and a sharpened stake that may have been used by a hungry hunter to kill the animal 12,000 years ago.

In 1986, Gifford and his colleagues recovered a skull with brain tissue from what he thinks was an ancient burial in shallow water near the spring. He continues to work with DNA samples to determine the date of the find.

Gifford and other archaeologists found more from the tortoise this past July, along with the slaughtered remains of a giant ground sloth.

The discovery of the sloth's bones, Gifford said, could indicate that Little Salt Spring was a sort of ancient butcher shop where hunters often killed their prey and prepared meat when this was dry land.

These remains come from the earliest known period of human activity in the Western Hemisphere, said Gifford, who has received funding for his work from the National Geographic Society's Committee for Research and Exploration. (National Geographic News is owned by the National Geographic Society.)

"This is a warehouse of environmental, natural, historical, and archaeological remains in a very, very well preserved environment," said Roger Smith, Florida's state underwater archaeologist.

"That's why it's a world-class site. I would call it a portal back into time."

(Watch a video about Ice Age people in Florida.)

The Sinkhole State

Sinkholes in Florida form when water from underground aquifers dissolves the porous limestone bedrock and pushes toward the surface. Eventually, the ground collapses into the water and an hourglass-shaped sinkhole is formed.

Florida has more springs than any other state in the U.S. Some are quite large, while others—such as Little Salt Spring—are smaller, at 243 feet (74 meters) wide. Because the spring water comes from underground, it stays at a constant temperature of 75 degrees Fahrenheit (24 degrees Celsius).

When Little Salt Spring was formed during the last Ice Age, sea level was lower and what is now the Florida peninsula was much wider. Sources of freshwater were scarce. Ancient Native Americans came to the sinkhole to drink the water and perhaps find a meal.

"Florida was much drier than it is today," Gifford said. "Essentially, [Little Salt Spring] was an oasis." Gifford and his divers worked last summer on a ledge about 90 feet (27 meters) below the surface where the stake and tortoise remains were found.

Ancient Environment

Gifford's divers will return to lower depths of Little Salt Spring soon, but will wait until their recent finds have been analyzed. They hope to eventually uncover evidence of campfires on the ledge. And because Little Salt Spring's waters contain little or no oxygen that would support bacteria that eats away at artifacts, it's possible they'll find near pristine items.

"There may be lots of stuff—basketry, woven fabrics, wooden implements—that you wouldn't otherwise find in an archaeological context," said Bruce Smith, curator of North American Archaeology at the National Museum of Natural History in Washington, D.C.

Finding fragile wooden artifacts would "open a new window" of understanding how early Native Americans lived, Smith said. "You can really get excited by it."

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