10,000-year-old stone tools unearthed in Washington State

More than 4,000 stone flakes, scrapers, awls and spear points were found, dating back to a time when its inhabitants roamed the same lands as shaggy-haired mammoths and prehistoric bison.

"We were pretty amazed", said archaeologist Robert Kopperl, who led the field investigation, to The Seattle Times. "This is the oldest archaeological site in the Puget Sound lowland with stone tools".

The excavation took place near the shores of Bear Creek, a tributary to the Sammamish River, a 10-minute drive from Microsoft headquarters. Kopperl and his team published their initial findings earlier this year in PaleoAmerica .

During the last glacial age , an ice sheet around a mile thick blanketed the Puget Sound region. However, 10,000 years ago, the ice age was coming to a close, and ice had already retreated from the area. In its wake, small groups of inhabitants were left with Lake Sammamish, its marshy fringes and plenty of pine forests.

The ancient stone tools were found after digging through a foot-thick layer of peat. "It's hard to find this kind of site west of the Cascades, because it's so heavily vegetated and the Puget Lobe of the big ice sheet really affected the landscape", said Kopperl.

Chemical analysis of one of the stone tools found traces of food, which suggested the inhabitants ate a diet rich in bison, deer, bear, sheep and salmon. Once the researchers have analyzed the remaining artifacts, they will hand them over to the Muckleshoot Tribe for curation.

The dig unearthed a single salmon bone fragment, an emblematic reminder of the project’s vital objective, added Kopperl: "Since finding the site was based on a salmon-restoration project, it’s kind of like coming full circle".