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CORVALLIS - They look a little like trash, and indeed that's what some of them are. A visitor to the Oregon coast didn't need them and cast them aside, probably not even looking at where they fell and were later picked up by researchers from Oregon State University.

But these aren't a pop can and chip bag cast carelessly aside by a thoughtless contemporary tourist. This tourist visited the Oregon coast roughly 12,000 years ago and left behind chips of rock at the spot where he or she had fashioned a stone tool. This collection of tiny stone flakes - along with what researchers call "expedient tools" and other signs of their presence - form an exciting piece in a jigsaw puzzle that may some day tell us how humans first came to the Americas.

The pieces of stone are the latest finds in a long-term study of a site on the southern Oregon coast. The research has been led by OSU anthropology professor Roberta Hall and funded by Oregon Sea Grant.

These stones and fragments - which now rest in plastic bags in OSU's archaeology lab - are signs of human activity in a place where people had not previously been known to have visited for another 2,000 years.

The OSU team caused a stir far beyond the coast when they found the first artifacts in 2002. Further work at the Indian Sands site in the summer of 2003 brought back a treasure trove of further relics adding to a growing body of evidence that is changing our understanding of how and when humans populated the Americas.

Most adults can still recall the elementary school lessons in which they learned about humans first arriving in North America via a land bridge from Asia and populating the interior of the continent, then spreading out. During the last Ice Age, so much water was locked up in glaciers that the seas were as much as 300 feet lower. A landmass between Alaska and Siberia - known to scientists as Beringia - would have made travel between the two continents possible.

But not all of the facts uncovered by researchers fit neatly into that theory, raising some thorny questions. Of particular significance is a site in Chile that has been reliably dated to 14,000 years ago, completely out of the time scale for the land-bridge theory. Researchers have advanced another theory, suggesting that early inhabitants traveled by boat north along the coast of Asia during late Pleistocene times, and then south along the Pacific Ocean's North American coast.

Oregon would have been one of their early stopping points on this continent.

A major problem in testing this theory is that most of what was the Oregon coast thousands of years ago is now under water. As the glaciers of the last Ice Age melted, the released water raised the level of the ocean. What was once attractive seaside real estate is now anywhere from hundreds of feet to more than a mile offshore.

Hall and her fellow researchers began looking for a site on the state's shoreline to test their theory. They knew that any landing place by such early visitors must be submerged by now. So they looked for something that might have drawn visitors inland. The Indian Sands site in Boardman State Park, about 12 miles north of Brookings on the southern Oregon coast, caught their eye. Geologic tests indicated it would have been a good source for tool stones.

Loren Davis, a geoarchaeologist who is an instructor in OSU's anthropology department and field director on the project, picked the spot after two years of studying, including soil and radiocarbon testing.

The first excavation yielded pay dirt in the form of bits of charcoal that were radiocarbon dated to 12,000 years ago (Radiocarbon tests typically understate actual age, Hall said, so the 10,430 year RC result corresponds to about 12,000 actual years ago.), along with some 130 or so flakes of stone that showed clear signs of having been chipped away from a larger stone in the making of a tool. The news made headlines, and more work was planned at the site for the following summer.

In 2003 six excavations were made at the site in an area about 30 meters by 30 meters. According to Sam Willis, the graduate student who is doing the lithic analysis for the project, almost 3,000 pieces of rock bearing obvious evidence of human handling were unearthed from the proper levels of the dig.

Further, the researchers found traces of obsidian flakes that analysis shows came from the Klamath Basin and northern California. These indicate a degree of mobility and knowledge of the region that is exciting, Willis said, as it indicates that whoever was making that tool might have been a settler, rather than a brief visitor. "They either knew the region or they knew people who knew the region," he said.

Either way, the researchers add, it's an exciting piece of evidence to add to the puzzle.