LEE HOCHBERG, NewsHour correspondent: What archaeologist Dennis Jenkins found in the Paisley Caves in south central Oregon may turn on its head the theory of how and when the first people came to North America.
Many scientists believe humans first came to this continent 13,000 years ago across a land bridge from Asia and they started the so-called Clovis culture. But Jenkins says they may have been living in these caves 1,000 years earlier, toward the end of the last ice age.
DENNIS JENKINS, archeologist: We certainly knew that people had lived in the caves, but we did not have adequate dating to prove that they were here at the end of the ice age.
LEE HOCHBERG: In 2002, he and his students at the University of Oregon began excavating the caves looking for proof. They discovered 14,000-year-old camel bones and signs they’d been butchered by humans. And then, they found artifacts of the humans themselves.
DENNIS JENKINS: It even includes on the top of it what’s probably a chunk of feces.
LEE HOCHBERG: Although it was hardly the stuff of Indiana Jones.
DENNIS JENKINS: We were looking and hoping, of course, to find spear points, evidence of their technology. Instead, what we found was the perfect human signature, their coprolites. It was, if you will, the perfect artifact.
LEE HOCHBERG: Coprolites are an archeology term for fossilized feces. Jenkins says they’re from humans, and they’re more than 14,000 years old.
DENNIS JENKINS: So this was the evidence we had dug all summer to get to.
LEE HOCHBERG: It’s not the first time this area of Oregon has given up clues suggesting humans were here earlier. Seventy years ago, another Oregon archaeologist, Luther Cressman, found these sandals in the cave woven from sagebrush bark.
LUTHER CRESSMAN, archaeologist: Now, the interesting thing here is that we have a toe flap. The toe fit in here.
LEE HOCHBERG: And he found stone tools that carbon dating suggested were from the Pleistocene age, more than 13,000 years old.
LUTHER CRESSMAN: And to find these things down here at Fort Rock Cave, at 13,200 years ago, means that the people were down in the great basin before the last glaciation. That’s why these things are so important.
Human diet clues from DNA tests
LEE HOCHBERG: But other scientists said the evidence wasn't definitive enough to prove humans were here at that time. And instead, the theory of the land bridge took hold.
DENNIS JENKINS: I'm going to pull it out. It looks just like what it is.
LEE HOCHBERG: In 2004, Jenkins and his colleagues took their new evidence, the coprolites, to the university lab to see if modern science could offer more answers. They found the coprolites reflected a human diet.
DENNIS JENKINS: Here we have bone, some hair, vegetation, material. Those are all good indicators that it's a human coprolite.
LEE HOCHBERG: Carbon dating showed three of the coprolites, and the animal bones found with them were 14,300 years old. And DNA tests showed six samples with distinct markers of ancient Native Americans.
Three hundred additional coprolites the team recovered are now being analyzed. Jenkins says he's confident he's found the earliest evidence of humans in North America, who look like either current Native Americas or like Paleo-Indian people.
DENNIS JENKINS: They were probably somewhat shorter than we are, 5'5", 5'6", perhaps. They would have been wearing clothing like we are that was made out of hides or perhaps bull rush.
We found little tiny threads that were .04 millimeters, I mean, so tiny they're as small as the threads in your shirt. Clearly, people were sewing their clothing, form-fitting clothing just like we have, shirts, pants, those kinds of things, perhaps moccasins.
LEE HOCHBERG: And he says their coprolites show they ate desert parsley, which grows six inches under the ground.
DENNIS JENKINS: The fact that they were exploiting that plant just like the Native Americans of this region were doing at later times tells us that they were very well-adapted to their environment. These were not explorers. These were people who were living in this area. They were at home here.
LEE HOCHBERG: And perhaps most importantly, they would have had to have come here in a different way than long believed. Since at that time the continent was covered under an ice sheet miles thick, land travel from the land bridge south would have been impossible.
The early humans would have had to come by boat to the Pacific coast and then traveled inland through a strip of warmer swampland. Early peoples are thought to have arrived in Australia by boat, but it's a new idea for America.
Coprolites' importance debated
LEE HOCHBERG: And yet, for all of the excitement, the findings are controversial. Skeptics argue that human DNA found in the 14,000-year-old specimens may have actually been deposited here thousands of years later.
Anthropologist Gary Haynes of the University of Nevada-Reno says the coprolites might, indeed, be from the ice age, but actually come from wolves or dogs, and then been contaminated later by early Indians.
GARY HAYNES, anthropologist: Native Americans have lived in this rock shelter for thousands of years afterwards. There could have been contamination through the dirt, leaching DNA. Native Americans have been living, and eating, and defecating, and urinating, and sweating, and just living in that shelter for thousands of years.
LEE HOCHBERG: And Haynes is bothered by the lack of evidence of a broader society. After all, with Clovis culture, scientists discovered distinctive spear points next to mammoth bones in many locations across the American West, Mexico and Central America. Why not for the Paisley Caves?
GARY HAYNES: Where are the stone tools? Where's the thing that everybody in the rest of the world is doing and making at 14,000 years ago? That's what's missing.
It's a coherent set of artifacts that nobody would doubt were made by people, which is what the coprolite sites don't have.
LEE HOCHBERG: Jenkins answers that he conducted protein tests on the coprolites that verify they're human, not canine. And he says with new forensic science, finding spear points might not be as important as it used to be.
DENNIS JENKINS: We don't know what their spear points are yet, but that doesn't mean that they weren't here. We've got their coprolites. We've got their cells.
LEE HOCHBERG: They're just as good as tools?
DENNIS JENKINS: They are the ultimate artifact, in my opinion. I've really come to like coprolites.
LEE HOCHBERG: Jenkins believes his theory, published recently in Science magazine, will become widely accepted, but it will take a few years to erode archaeology's deeply entrenched Clovis-first bias.
DENNIS JENKINS: For 60 or more years, we have had the concept that Clovis was first. And it made such a nice package that it was very believable. And the Clovis door has now been jarred apart. And if this evidence holds and is not disproven, then there's no way you're going to close it again.
LEE HOCHBERG: Jenkins is going to gather more Paisley Cave samples this fall and try to link his discovery to other pre-Clovis finds in Chile.