Archaeologists have uncovered a stone tool in Oregon that suggests humans occupied the western US earlier than thought . The agate tool was uncovered under a thick layer of volcanic ash dating back to the eruption of Mount St Helens 15,800 years ago . Scientists believe the primitive knife , discovered 12ft ( 3.6 metres ) below ground , was used for cutting animal hides , butchering meat , and carving wood by pre-Clovis people . Archaeologists have uncovered a stone tool in Oregon that suggests humans occupied the western US earlier than thought . The agate tool was uncovered under a thick layer of volcanic ash dating back to the eruption of Mount St Helens 15,800 years ago . The find , at Rimrock Draw Rockshelter , was announced today by the U.S. Bureau of Land Management , which controls the land on which the site was found . Archaeologist Scott Thomas said that if the age of the area holds up to scrutiny , it would be the oldest pre-Clovis find west of the Rockies . It would also be older than another predating the so-called Clovis culture , once generally believed 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 . Professor Patrick O'Grady from Oregon University called the find 'tantalising . ' The find , at Rimrock Draw Rockshelter , was announced today by the U.S. Bureau of Land Management , which controls the land on which the site was found . Archaeologist Scott Thomas said that if the age of the area holds up to scrutiny , it would be the oldest west of the Rockies . 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 skeptical . Two pre-Clovis sites are well documented and generally accepted by scientists . One is Paisley Cave , located 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 date 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 . Much of discoveries at these sites indicate the people were involved in hunting , gathering and fishing , for which they used bone tools . Some sites suggest that pre-Clovis people sometimes lived in hut clusters . Many were situated along the coastline , suggesting a marine lifestyle . Many archaeologists favour the theory that they came over the Bering Strait crossing from northeastern Asia . '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 . ' Two pre-Clovis sites are well documented and generally accepted by scientists , Grayson said . One is Paisley Cave , located 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 date 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 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 . He said he noticed an outcropping of an ancient lava flow , with some very tall sage brush growing in front of it , indicating very deep sediment deposits . Rimrock Draw Rockshelter is located near Riley Oregon in Harney County in southeast Oregon . If the date 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 soil was black in front of the rock , indicating someone regularly built cooking fires there for a long time . 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 . Volunteers looking around the surface found some 30 stemmed points , and the field school started excavations in 2011 , O'Grady said . Uncovered above and below the volcanic ash layer were fragments of teeth believed to be from ancient camels . Tests by Archaeological Investigations Northwest of Portland on blood residue on the agate scraper were consistent with the bovid family of animals , Thomas said . The most likely bovine animal living in Oregon at that time would have been an ancestor of the buffalo .
The agate tool was uncovered under a thick layer of volcanic ash . It was used for cutting hides , butchering meat , and carving wood . Find was made at Rimrock Draw Rockshelter in southeast Oregon . If the date of Rimrock holds up , it would put people at the site about 1,500 years earlier that thought , at the end of the Pleistocene era .