SCIENCE -- July 12, 2012 at 4:08 PM ET
Oregon Cave Yields New Clues to Earliest Americans
University of Oregon archaeologist Dennis Jenkins holds three ancient tools known as Western Stemmed projectiles from the Paisley Caves in Oregon. Photo by Jim Barlow.
It was long thought that the Clovis people were the first North American human settlers, and that they appeared on American soil some 13,000 years ago after traveling across a land bridge from Asia. They preyed on extinct mammals like the mastodon, used distinctive stone tools and were named after a town in New Mexico, where those tools were first found.
But archeologists have unearthed strong evidence of another group of early Americans with their own distinct technology, from the Paisley Caves in Oregon's Northern Great Basin. The area, a volcanic region located on the eastern side of the Cascade Mountain range, is so arid and the caves so dry that artifacts and ancient remains have been extremely well preserved over time.
In 2008, scientists from the University of Oregon and the University of Copenhagen found dried feces, from which they extracted human mitochondrial DNA, dated 14,300 years ago. They published their results in the journal Science. But the results at the time sparked debate among scientists in the field: Could the material have been contaminated by younger DNA - urine, for example, that leached through the cave deposit? And could material in the cave have churned up over time, upsetting the levels and confusing the dates?
In the years since, archeologists have dated 190 objects - artifacts, bones, sagebrush twigs and ancient dried feces, also known as coprolites - from silt in the ancient caves. Among the objects dug up were discarded tools called Western stemmed projectile points, believed to have derived in form from even older tools in Asia and Siberia.
"It's absolutely phenomenal that anything 14,000 years old can be found," said Dennis Jenkins, the study's lead author. "Usually we think of poop as disappearing pretty quick. In this case, we also have camel bones of the same age with blood, fat and sinew attached to them."
A new paper published Thursday in the journal Science addresses the original questions. Thomas Stafford, a geologist from the University of Oregon, extracted water soluble material from samples of the coprolites by soaking them "like a tea bag" in distilled water, thus extracting the potentially contaminating carbon from the feces, and then radiocarbon dated both remaining parts. And he found "no substantial evidence" of younger DNA being carried into the material.
It's absolutely phenomenal that anything 14,000 years old can be found.
--Dennis Jenkins, University of Oregon
"The hypothesis is that if water is moving down through the deposit, then the material we were going to date from the distilled water should be younger than the material in the coprolite," Jenkins said. "What we found is that in 11 out of the 12 cases, it was older or the same age."
And as to whether it was churned up, more than 100 radiocarbon dates taken from cave samples showed that the deposits had remained in chronological context, said Jenkins, which was consistent with their findings. One sample of human feces dated to 13,100 years old was found in the same stratum as the oldest Western stemmed projectile point. And five centimeters down, in the deposit, another sample of feces dated at 13,230 years old.
But Just as striking is what wasn't found in the Paisley Caves: any defining features of the Clovis culture.
"The big 'aha'," Jenkins said, "is that we have demonstrated that these Western Stemmed projectile points are the same age as Clovis." And while they overlapped in time, he added, there is no evidence of Clovis or any precursor to Clovis in the cave, indicating that these tools were made and passed on by a different group of people.
"How different, we don't know," Jenkins said. "We don't know what language these folks spoke or an awful lot about them - or how they thought or how they organized themselves."
Tom Dillehay, an archeologist with Vanderbilt University, who was not involved with the research, said of the finding: "This is another database that shows this regional diversity very early on...In North America, people have been reluctant to buy into cultural diversity. Until several years ago, the Clovis-first model dominated. "
But Dillehay added that he's still puzzled as to why scientists haven't identified more human artifacts at the deeper levels.
An important question for future research will be learning more about where the early settlers arrived from. While genetic evidence still clearly points to Siberia and Asia, "that does not mean that there might not have been secondary or tertiary migrations of people coming in from other places," Dillehay said. "And that may help account for the different regional and cultural diversity that we're seeing."
Correction: An earlier version of this story incorrectly identified where the first Clovis remains were found.