In 2008, researchers reported finding fossilized human feces in a cave in southern Oregon dating to roughly 14,300 years ago. The finding challenged the long-held scientific consensus that humans first arrived in the Americas around 13,000 years ago. The material was found in the Paisley Five Mile Point Caves in Lake County, a series of shallow openings in a volcanic ridge near the dried bed of Summer Lake.
The caves were first excavated in the late 1930s by Luther Cressman, an archaeologist from the University of Oregon. Cressman recovered tools, animal bones, and other evidence of early human habitation, but the radiocarbon dating method had not yet been invented, so he could not determine the age of the deposits. The caves were largely left untouched for decades afterward.
Beginning around 2002, University of Oregon field archaeologist Dennis Jenkins reopened the site with his students. Among the bones and stone tools, the team found coprolites, the scientific term for fossilized excrement. Radiocarbon dating indicated the oldest samples were roughly 14,300 years old, more than a thousand years older than the timeline accepted by most archaeologists at the time.
The dominant theory in American archaeology for most of the 20th century was known as Clovis First. It held that the first Americans were big-game hunters who crossed a land bridge from Siberia to Alaska during the last ice age, then moved south through an ice-free corridor. The theory was based on distinctive fluted spear points found near Clovis, New Mexico, dating to about 13,000 years ago. Claims of older sites had repeatedly failed to hold up under scrutiny, and many researchers demanded unusually strong proof for any older evidence.
Skeptics raised several objections to the Paisley find. Ancient DNA is easily contaminated by modern genetic material, and the caves had been visited by many people over the decades. Water moving through cave sediment could also carry organic material from younger layers down into older ones. In addition, the earliest Paisley layers did not contain the Clovis-style spear points that supporters of the dominant theory expected, which raised doubts about whether the site was genuinely pre-Clovis.
Jenkins responded by tightening his methods. His team adopted sterile excavation procedures, took control samples, and tested the genetic profiles of the dig crew to rule out contamination. Independent laboratories were brought in to verify the results. The coprolites themselves were dated directly, and the sediment chemistry was tested to determine whether water movement had disturbed the layers. The dates remained consistent.
Genetic analysis was carried out by Eske Willerslev, an ancient DNA researcher at the University of Copenhagen. The DNA recovered from the samples was human and carried maternal lineages, known as haplogroups A and B, that are found in Native American populations and in ancient populations of Northeast Asia. This linked the people who left the material to the ancestral populations of the Americas.
In 2012, Jenkins, Willerslev, and a large team published a follow-up study in the journal Science. By that point, excavations had also produced stone tools from the older layers, but they were not Clovis points. They were Western stemmed points, a different tool-making tradition shaped with a different technique. The dating indicated that both traditions existed at roughly the same early period. This suggested that Clovis was not the single ancestral culture from which all later Indigenous American societies descended, and that more than one distinct population had been present in the Americas at that early date.
A French genetics laboratory published a challenge to the findings, arguing that the human DNA might be modern contamination. Jenkins and his colleagues answered the challenge in the scientific literature, presenting evidence that the ancient human signal remained consistent after multiple checks.
The Paisley findings changed the way researchers treated other pre-Clovis sites. The Buttermilk Creek Complex in Texas, where tools were found beneath a Clovis layer, and Monte Verde in Chile, which had been disputed for years, were among the sites that received renewed attention as part of a broader pattern.
The outcome of the Paisley investigation did not rest on a single dramatic artifact. It came from material that is normally disregarded, preserved for thousands of years by dry conditions, and analyzed through careful laboratory work that addressed each objection directly. Cressman had excavated the caves decades earlier, but the techniques and the interpretive framework needed to understand what he had found did not exist at the time.
The wider significance of the Paisley evidence is that the story of how the Americas were first peopled is more complex than a single migration along one route at one moment. The existence of the Western stemmed point tradition at the same age as Clovis raises open questions about whether separate groups arrived by different routes, possibly including coastal travel, or whether humans had been present in the Americas long enough for distinct traditions to develop from a common origin. These questions remain unresolved.
