Stone tools discovered by archaeologists at the Rimrock Draw Rockshelter in Oregon suggest that the site could be the oldest known site of human occupation in western North America, the US Bureau of Land Management announced on Thursday.
The rockshelter, which is controlled by the Bureau, is located near the community of Riley in the high desert region of eastern Oregon, and the tool – a hand-held scraper chipped from a piece of orange agate not ordinarily found in the region – was discovered buried underneath an eight-inch layer of volcanic ash from an eruption of Mount St. Helens over 15,000 years ago.
BLM archaeologist Scott Thomas told the Associated Press that if the site’s age is confirmed, it would be the oldest ever discovered west of the Rocky Mountains, predating the Clovis culture previously believed to have been the first population to migrate to North America from Asia. The earliest artifacts from that civilization have been dated to roughly 13,000 years ago.
A tantalizing find
University of Oregon archaeologist Patrick O’Grady, who supervises the dig, said that the find was “tantalizing,” but cautioned that the site had not been fully excavated. He told the AP that he wanted to determine whether or not the volcanic ash covered the entire region.
The tool, which was found near the bottom of a 12-foot deposit, is believed to have been used for scraping animal hides, butchering, and possibly carving wood, the researchers said in a statement. They conducted a blood residue analysis of the scraper and discovered animal proteins consistent with bison, most likely an extinct ancestor of the buffalo known as the Bison antiquus.
The undisturbed volcanic ash under which the tool was buried was dated to 15,800 years ago, which would indicate that the scraper itself is at least that old, Thomas said. That would make it older than dried feces found in Oregon’s Paisley Cave in 2008, which contained DNA that was more than 14,000 years old, according to the BLM.
The oldest in North America
“When we had the volcanic ash identified, we were stunned because that would make this stone tool one of the oldest artifacts in North America,” O’Grady said. “Given those circumstances and the laws of stratigraphy, this object should be older than the ash.”
“While we need more evidence before we can make an irrefutable claim,” he continued, “we plan to expand our excavation this summer and hopefully provide further evidence of artifacts found consistently underneath that layer of volcanic ash. That’s the next step.”
Donald Grayson, professor of archaeology at the University of Washington, told the AP that the discovery would be met with skepticism from the scientific community. He added that no one would believe it until the archaeologists can prove that there was no break in the ash layer it was buried under, and that there was no way that the tool worked its way down from above.
However, Stan McDonald, BLM Oregon/Washington lead archaeologist, insisted that the find had tremendous potential for the archaeological community. For several years, he said, many in the field insisted that the Clovis were the first people to reach the western hemisphere.
“While a handful of archaeological sites older than Clovis cultures have been discovered in the past few decades, there is still considerable scrutiny of any finding that appears older,” he added.
“With the recent findings at Rimrock Draw Shelter, we want to assemble indisputable evidence because these claims will be scrutinized by researchers.”