A pre-Clovis presence
In the high desert of south-central Oregon, a series of eight caves holds evidence that rewrites the timeline of human arrival in the Americas. The Paisley Caves, wave-cut shelters in a ridge of Miocene and Pliocene basalt, were first investigated by archaeologist Luther Cressman in the 1930s. But it was excavations beginning in 2002 by a University of Oregon field school, led by Dr. Dennis Jenkins, that uncovered the most significant finds: desiccated human feces, or coprolites.
Radiocarbon dating of these coprolites established their remarkable age. The oldest samples date back to 14,300 calendar years before present. This places people in North America more than 1,000 years before the appearance of the Clovis people, a culture long considered to be the continent's first. The discovery directly challenges the "Clovis-first" model, which posited that humans first populated the Americas around 13,000 years ago. Along with the coprolites, researchers found a small rock-lined hearth and numerous bones from waterfowl, fish, and extinct Pleistocene mammals like camels and horses, all about 7 feet below the modern cave floor.
The DNA evidence and debate
The coprolites provided a date; they contained the oldest human DNA ever recovered in the Americas. Analysis led by geneticist Eske Willerslev of the University of Copenhagen identified mitochondrial DNA from Native American haplogroups A2 and B2, which are common in Siberia and East Asia. This genetic evidence links these early inhabitants to Asia, supporting the Bering Land Bridge migration theory but at a much earlier date.
The findings were not without controversy. Some scientists questioned if the human DNA could be a result of contamination, where water leached more recent DNA down through the soil layers into the older coprolites. To address this, Jenkins' team conducted extensive further testing. Over 190 radiocarbon dates were taken from the caves to confirm the sediment layers remained in chronological order. Later studies analyzed fecal lipids—organic compounds less mobile than DNA—which confirmed the human origin of three of the pre-Clovis coprolites. In the same ancient sediment layers as the coprolites, archaeologists also found Western Stemmed Tradition projectile points, a stone tool technology distinct from and at least contemporaneous with Clovis tools.