For much of its length, the slow-moving Aucilla River in northern Florida flows underground, tunneling through bedrock limestone. But here and there it surfaces, and preserved in those inky ponds lie secrets of the first Americans.

For years adventurous divers had hunted fossils and artifacts in the sinkholes of the Aucilla about an hour east of Tallahassee. They found stone arrowheads and the bones of extinct mammals such as mammoth, mastodon and the American ice age horse.

Then, in the 1980s, archaeologists from the Florida Museum of Natural History opened a formal excavation in one particular sink. Below a layer of undisturbed sediment they found nine stone flakes that a person must have chipped from a larger stone, most likely to make tools and projectile points. They also found a mastodon tusk, scarred by circular cut marks from a knife. The tusk was 14,500 years old.

The age was surprising, even shocking, for it suddenly made the Aucilla sinkhole one of the earliest places in the Americas to betray the presence of human beings. Curiously, though, scholars largely ignored the discoveries of the Aucilla River Prehistory Project, instead clinging to the conviction that America’s earliest settlers arrived more recently, some 13,500 years ago. But now the sinkhole is getting a fresh look, along with several other provocative archaeological sites that show evidence of an earlier human presence in the Americas, perhaps much earlier.

Which is why I found myself on the banks of the Aucilla with Michael Waters, director of the Center for the Study of the First Americans at Texas A&M University. A tall, unassuming 57-year-old, with an easy confidence honed during more than 30 years in the field, he had organized archaeologists and divers to gather more evidence of the sinkhole’s role in prehistory. “This site is as old as anything in North America,” Waters said. “The context is fine, and the dating is fine, but people just looked at it and said, ‘Hmm, that’s interesting,’ and that was it. It had a lot of potential, but it was in limbo. We’re here to confirm the earlier work, and if we’re lucky, we’ll find some more artifacts.”

Waters’s team, led by Texas A&M underwater archaeologist Jessi Halligan, worked at the Page-Ladson sink, named for Buddy Page, who discovered it, and John Ladson, the property’s owner. The sink lies 30 feet below the opaque surface of the Aucilla, which, following heavy rains, was dyed nearly black by humus from the hardwood hammock. Fish were jumping in the water, while birds, turtles and the occasional gator patrolled nearby. Were it not for Halligan’s divers, there would be no human presence and the silence would be absolute.

Underwater archaeological sites are staked out and marked in meter-square quadrants, just like open-air excavations. The mud, troweled away by one diver, was fed into the mouth of a four-inch suction dredge held by a second diver. The dredge discharged into a pair of mesh screens mounted on a skiff moored in midstream. Big pieces—stones, bones, leaves and perhaps human artifacts—collected on the top screen, a quarter-inch mesh, and the small stuff was caught by the sixteenth-inch mesh below.

First the researchers had to clear the site of the detritus that had accumulated in the 15 years since the first excavation ended. Then, to reach the most promising level, divers removed a ten-foot layer of clay that overlay it. The work was tedious—“like diving in dark roast coffee,” said James Dunbar, an archaeologist and member of the original Aucilla team who’d returned for a second look—but the blanket of sediment guaranteed the site’s integrity. Everything below the sediment was as old as the people who left it there. In the oxygen-deprived deposits within the Aucilla mud, nothing decays.

Working in the Stygian gloom with lamps and suction pumps, the divers unearthed a number of small bone fragments, the fist-size vertebra of a large mammal and a manhole cover-size shoulder blade that might have belonged to the same mastodon whose tusk bore the cut marks of the ancient hunters. Also recovered in the fine-mesh screen were many pounds of mastodon digesta, the remains of vegetation that the six-ton beast ground to a mulch-like texture and swallowed.

The observations the researchers made in their days at the sinkhole validated the original excavation. (And on a subsequent expedition they found more mastodon bones.) Each new discovery generated fresh enthusiasm. “All we need now,” said Halligan, “are more human artifacts.”

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