An ancient stone tool recently discovered in the high desert of southeast Oregon has archaeologists raising their eyebrows.
The tool, a hand-held scraper chipped from a piece of agate, was unearthed from beneath a layer of volcanic ash near the Rimrock Draw Rockshelter outside Riley, the U.S. Bureau of Land Management announced on Thursday. Archaeologists have linked the ash to a major eruption from Mount St. Helens that occurred about 15,800 years ago.
“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," Dr. Patrick O’Grady, an archaeologist at the University of Oregon and the leader of the excavation, said in a written statement. "Given those circumstances and the laws of stratigraphy, this object should be older than the ash.”
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The scraper was found at an ancient rock shelter in the high desert of eastern Oregon. It could turn out to be older than any known site of human occupation in western North America.
The new finding may rewrite the story of early human migrations, as it was once previously thought that the first humans in the western hemisphere arrived about 13,500 years ago.
“For years, many in the archaeological field assumed that the first humans in the western hemisphere were the Clovis people – dating to around 13,000 years ago. 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,” Stan McDonald, the bureau's Oregon/Washington lead archaeologist, said in the statement.
If humans arrived more than 15,800 years ago, as the stone tool suggests, it would place humans in America's West around the end of the Pleistocene era, when mastodons, mammoths, camels, horses, and bison roamed the region, the Associated Press reported. But some scientists remain skeptical.
"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," Donald K. Grayson, professor of archaeology at the University of Washington, who was not involved in the excavation, told AP. "Until then, extreme skepticism is all they are going to get."
Archaeologists plan to continue excavations at the Oregon site this summer, O'Grady said in the statement, adding "that’s the next step."
This article has been updated with the quote from Stan McDonald, explaining the 13,500-year figure.