NORMAN, Okla. (AP) -- University of Oklahoma archaeologist Don Wyckoff considers himself cautious when it comes to questions about when humans moved into North America.
Scientists have long believed that human hunters known as Clovis people first tread this continent about 11,500 years ago. Those beliefs are based on artifacts found in the 1920s near Folsom, N.M.
But Wyckoff says he believes tools discovered in northwest Oklahoma date to at least 22,000 years ago.
While the discovery has been documented by newspapers, magazines and some small scientific journals, Wyckoff has protected the find up until now because he knows the kind of skepticism it will draw when released for review by his peers. But a monograph he plans to complete this summer will detail evidence of his theory.
"We didn't expect to find people there," said Wyckoff, associate curator of archaeology at the Sam Noble Oklahoma Museum of Natural History. "We were just trying to find out what Oklahoma was like before the last ice age. And all of a sudden, we findevidence of people."
Wyckoff was invited in 1986 to the Burnham Ranch near Freedom, in far northwest Oklahoma. Along with the fossilized bones from a variety of wildlife, Wyckoff's team found two broken stone tools among a scattering of 50 flakes of rock adjacent to a bison skull. It was all in a layer of sandy loam that once lined the bottom of an ancient watering hole.
Carbon dating on the snails surrounding the artifacts shows these diment layer was anywhere from 25,000 to 35,000 years old.
"Unfortunately, it wasn't the perfect circumstances," Wyckoff said. "They got washed out of where they originally were and into the pond."
Because of that, it's been harder for Wyckoff to conclusively date his find.
Excavations around the perimeter found no evidence of an encampment. But Wyckoff believes it still may be out there.
"They didn't wash very far. They couldn't have washed more than 50 feet," Wyckoff said. "They were all clustered around that bison."
Wyckoff also wishes he had more precise dates for the sediment layer from which he pulled the tools, but he is satisfied the artifacts are at least 22,000 years old. They were surrounded by a species of snail that died out in Oklahoma after the last ice age began 21,000 years ago.
Jim Theler, an anthropologist and archaeologist from the University of Wisconsin-LaCrosse, initially told Wyckoff he didn't believe the findings.
Despite the skepticism, Theler agreed to join the project, helping to identify snails that surrounded Wyckoff's artifacts.
"I suppose I still have some skepticism, but I don't have anyway to explain the materials except that those materials are thatage," Theler said.
Wyckoff has been careful and unbiased in his work. He won't face much criticism, Theler said.
"If he doesn't get it from me, he probably won't get it from anyone else, because I'm so conservative," Theler said. "I think he has a good case here." Wyckoff said he believes his evidence, as well as future discoveries of pre-ice age people, will change attitudes about American Indian people.
"I believe people have been here a lot longer than we give them credit for," Wyckoff said.