Robert D. Wall is too careful a scientist to say he's on the verge of a sensational discovery. But the soybean field where the Towson University anthropologist has been digging for more than a decade is yielding hints that someone camped there, on the banks of the Potomac River, as early as 14,000 B.C.
If further digging and carbon dating confirm it, the field in Allegany County could be among the oldest and most important archaeological sites in the Americas.
"You're talking about the time period of the first settlement of the New World by human beings," said Mark Michel, president of the Archaeological Conservancy. "It would be extremely significant if it pans out."
The discovery of a human presence in Maryland anywhere near 14,000 B.C. would feed the debate about when the continent was first peopled, and by whom.
For now, the age of Wall's find is still in doubt. Three radiocarbon dates taken from buried organic matter found there all suggest the site dates to roughly 14,000 B.C. But another, derived from charcoal found beside an ancient hearth at the same depth, was pegged to 7,000 B.C.
"Not as old as we thought," Wall said. The challenge now, he said, is to find another charcoal sample for more carbon dating along with a tool or other artifact whose design clearly shows its age.
Archaeologist Dennis Curry of the Maryland Historical Trust said scientists were taught for decades that the first humans came to North America after the last Ice Age ended about 13,500 years ago. According to the theory, they crossed a "land bridge" from Asia into what is now Alaska and spread quickly across the continent.
The theory is supported by the stone tools they left behind — all less than 13,500 years old. Their tool technology was named "Clovis" for the New Mexico town where it was first described.
But in the past decade, a handful of excavations in the eastern United States have turned up traces of different tools and encampments buried beneath the "paleo-Indian" sites of the Clovis people. Those materials are presumed to be older, or pre-paleo.
For example, burned wood found with tools at a Virginia site called Cactus Hill, south of Richmond, was dated to 16,000 B.C. Spear points and bone found in a rock shelter at Meadowcroft, Pa., near Pittsburgh, tested up to 19,000 years old.
But such finds have been controversial. Skeptics argue that the sandy soil at Cactus Hill might have allowed ground water to mix older organic matter with much younger artifacts, which would fool carbon-dating technology.
And the layering of deposits in rock shelters is notoriously complex. Meadowcroft's excavators might have simply confused older layers with younger ones.
A pre-paleo find at the western Maryland site would be harder to dispute, Curry said. On the floodplain where Wall is working, silt is deposited by the river, and the soil builds up over time. Ancient artifacts are buried in simple, stable, horizontal layers, with the oldest buried the deepest.