Excavations at the Rimrock Draw Rockshelter near Riley, Oregon — led by archaeologists from the University of Oregon and the Bureau of Land Management — have revealed stone tools and fragments of extinct animal tooth enamel buried beneath layers of volcanic ash and sediment that date back about 18,250 years before present. These finds include finely crafted agate scrapers, some with preserved organic residues, and tooth enamel from animals such as camel and bison, whose radiocarbon dates were calibrated to the late Pleistocene.
Because the stone tools and enamel were found beneath an ash layer linked to a Mount St. Helens eruption older than 15,000 years, researchers infer that humans were present in the region well before that time, making Rimrock Draw one of the oldest documented sites of human occupation in North America.
This evidence contributes to a growing body of archaeological data showing that people may have arrived and adapted to diverse environments across the continent significantly earlier than the traditional “Clovis‑first” timeline of around 13,000 years ago.
The discovery also highlights the careful stratigraphic context preserved in rock shelters, where successive layers of sediment act as a geological timeline, with deeper materials representing older periods of human and animal activity.
While the findings do not yet provide a complete picture of who these early inhabitants were or exactly how they arrived in North America, they support models of pre‑Clovis settlement and raise important questions about early migration routes, such as coastal corridors or earlier inland pathways.
Ongoing work at Rimrock Draw includes further testing of plant remains, stone artefacts, and additional tooth fragments, which may shed more light on how these people lived and interacted with their environment more than 18 millennia ago.
Overall, the Oregon discovery is reshaping understanding of early human history in North America, suggesting a deeper and more complex narrative of settlement than was once assumed.
