A stone tool was discovered at an ancient rock shelter in the high desert of Eastern Oregon, as site that appears to be older than any known site of human occupation in western North America, archaeologists said.
The discovery was announced last Thursday by the U.S. Bureau of Land Management, which controls the land on which the site was found.
Patrick O’Grady, the University of Oregon archaeologist who supervises the dig, said that the Rimrock Draw Rockshelter outside Riley has not been fully excavated. But the tool, a hand-held scraper chipped from a piece of orange agate not usually found in the area, was found about 12 feet below the surface and about 8 inches below a 15,800-year-old layer of volcanic ash from an eruption of Mount St. Helens.
According to Scott Thomas, Bureau of Land Management archaeologist that if the age of the site holds up to scrutiny, it would be the oldest west of the Rockies, and another predating the so-called Clovis culture, once generally thought to be the first people to migrate from Asia into North America. The earliest Clovis artifacts, known for distinctive and elegant stone points, are dated to about 13,000 years ago.
O’Grady called the find “tantalizing,” but he added that they want to continue digging this summer to see whether the volcanic ash covers the entire area.
Donald Grayson, professor of archaeology at the University of Washington, said the scientific community would be doubtful.
“No one is going to believe this until it is shown there was no break in that ash layer, that the artifact could not have worked its way down from higher up, and until it is published in a convincing way,” he said. “Until then, extreme skepticism is all they are going to get.”
Grayson said that there are two pre-Clovis sites which are well documented and generally accepted by scientists. One is Paisley Cave, about 60 miles southwest of the Rimrock site. The other is Monte Verde in Chile. Both are dated about 1,000 years before the oldest Clovis sites.
If the age of Rimrock holds up, it would put people at the site about 1,500 years earlier, at the end of the Pleistocene era, when mastodons, mammoths, camels, horses and bison roamed the area.
The find has yet to be submitted to a scientific journal for publication, but it has been reported in newsletters and at conferences, Thomas said.
Thomas found the site several years ago, while taking a break from carrying supplies to a session of the University of Oregon Archaeological Field School nearby that O’Grady was overseeing.
Thomas said he spotted an outcropping of an ancient lava flow, with some very tall sagebrush growing in front of it, indicating very deep sediment deposits. The soil was black in front of the rock, confirming that for a long time that someone regularly built cooking fires there. An ancient streambed ran by, which would have given people more reason to stay there. And on the surface, he found a stone point of the stemmed type, found at sites both older and younger than Clovis. Similar points have been found at Paisley Cave.