18,000-year-old shelter may be the oldest evidence of human occupation in the Americas

Two stone scraping tools were found buried deep beneath a layer of volcanic ash by the team.
Mrigakshi Dixit
Representational image of stone tools.
Representational image of stone tools.


Archaeologists have unearthed the oldest stone tools buried under thick volcanic ash in a rock shelter in Southern Oregon in the US. The radiocarbon dating suggests that these ancient artifacts were last used roughly 18,000 years ago.

The excavation work at the Rimrock Draw Rockshelter was carried out by a team of archeologists from the University of Oregon's Museum of Natural and Cultural History Archaeological Field School.

The stone tool findings make this location one of the Americas' earliest known human-inhabited sites.

Teeth fragments of prehistoric animals  

The team found two stone scraping tools buried deep beneath a layer of volcanic ash. The first was found in 2012, and the second in 2015 from a much deeper layer. 

The tools appear to have been skilfully shaped by ancient people from bits of orange agate.

Surprisingly, a deposit of dried bison blood was discovered near the borders of one scraper. 

This scraper was most likely discarded by the ancient person who used it after slaughtering the animal. And eventually, the artifacts got buried in the volcanic ash from an eruption of Mount St. Helens about 15,000 years ago. 

Previously, scientists discovered teeth remains of ancient mammals from the Pleistocene epoch at this same site. The teeth enamel fragments belonged to now-extinct cousins of current bison and camel.

Radiocarbon dating of teeth enamel fossils in 2018 and then again in 2023 produced intriguing results. The results revealed that ancient teeth date back to 18,250 years. 

18,000-year-old shelter may be the oldest evidence of human occupation in the Americas
Camel enamel fragment.

“The identification of 15,000-years-old volcanic ash was a shock, then Tom’s 18,000-year-old dates on the enamel, with stone tools and flakes below, were even more startling,” said Patrick O’Grady, lead archaeologist of this excavation work, in an official release.

The existence of these tools at this site implies that Rimrock Draw Rockshelter is one of North America's earliest human occupation sites.

Another known oldest site is reported to be in western Idaho, which suggests humans lived in the region about 16,000 years ago.

The official release mentions that the excavation at this site has been ongoing since 2011 under an official partnership agreement with the Bureau of Land Management.

“This is a very exciting development for the archaeological community,” said Heather Ulrich, BLM Oregon/Washington Archaeology lead.

Ulrich added: “Thanks to the partnership with Dr. O’Grady and the University these new dates push our archaeological knowledge of human occupation in North America even farther, perhaps the oldest yet!"

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