April 3, 2008
by Andrew Curry
Comments in the journal Science for July 10, 2009, have questioned the results reported here, but in the same issue, the original researchers reply to the criticisms and stand by their conclusions.
Ancient human coprolites yield surprisingly early dates
An unlikely source of information is helping to settle one of the most contentious debates in American archaeology: Who were the first people to colonize the Americas and when did they do it? Were they the mammoth-hunting Clovis people who lived 13,000 years ago, or some earlier group who archaeologists are just beginning to understand? A recent discovery in the Oregon desert announced in the April 4 edition of Science may end the debate once and for all. ARCHAEOLOGY contributing editor Andrew Curry visited Oregon's Paisley Caves in January to find out more. An excerpt of the story he filed is included here. Look for the full report in the July/August issue of ARCHAEOLOGY magazine.--The Editors
Dennis Jenkins excavating part of Paisley Caves. Jenkins found bones, stone tools and hundreds of coprolites--fossilized feces--at the Oregon site. (Dennis Jenkins)
On a sunny, freezing-cold afternoon in late January, I turned my rented SUV off Oregon State Highway 31 and onto an unmarked dirt road. I was soon bumping through sagebrush and snow across a rutted lakebed that's been dry for the last 12,000 years. After about 20 minutes, I pulled into the shadow of a brown butte where I met Dennis Jenkins, an archaeologist from the University of Oregon.
Jenkins led me halfway up the butte over a cascade of sharp gravel to a trio of dusty caves. They are nothing special to look at: just a few meters deep and barely tall enough to stand up in, they would have been temporary shelters at best.
Which is fine, because a few minutes would have been all someone needed to leave behind what may be the oldest evidence of human presence in the Americas 14,300 years ago. In a study published April 4 in the journal Science, Jenkins and University of Copenhagen geneticist Eske Willerslev argue that the artifacts were made by the ancestors of modern Native Americans, then deliberately left behind in southern Oregon's Paisley Caves.
Which is not surprising, really, because the artifacts in question are pieces of crap.
University of Oregon archaeologist Dennis Jenkins holds a human coprolite found at Paisley Caves. (Andrew Curry)
This unlikely story starts in 2002, when Jenkins was leading a field-school excavation of Paisley Caves, a row of eight shallow basalt holes overlooking a prehistoric lakebed. Six feet below the cave floor, Jenkins and his 26 students uncovered fragments of prehistoric life: camel and horse bones, sage grouse, mountain sheep and antelope bones with cut marks on them, tiny fragments of sewing thread, a handful of what looked like stone tools and more than a dozen oval, organic items that were exactly what they looked like: dried-up feces. (Polite archaeologists like to call them "coprolites" when writing up excavation reports and grant applications.)
By themselves, coprolites are nothing unusual. So when Jenkins got a call from a contact at the Bureau of Land Management saying an Oxford University graduate student was interested in experimenting on coprolites with a new DNA extraction technique, Jenkins was willing to give him a shot--but extremely skeptical anything would come of it. "I didn't know this guy from Adam," Jenkins says. "I'm open to new science, but not open to being labeled some kind of fringe scientist."
The grad student--Willerslev, an enthusiastic Dane known among his colleagues for his friendly personality, foul mouth and outstanding research--flew to Oregon in 2004 to take samples. "I was positively surprised. Some of the animal bones still had soft tissue on them, which indicated it was a really good preservation environment," Willerslev says. "And I'm not a morphologist, but some of the coprolites looked pretty human."
And that was that, for a while. In 2005 Willerslev moved home to Denmark, where he became the youngest full professor at the University of Copenhagen thanks to his pioneering work on ancient DNA. The Paisley coprolites sat in storage while Willerslev and his team searched for DNA at the bottom of the Greenland ice cap and teased mammoth DNA from grains of Siberian permafrost. "The coprolites were lying in my freezer for quite some time," Willerslev admits. "To be honest, I didn't think they would be that interesting."
Eske Willerslev in his University of Copenhagen lab. Sequencing ancient DNA requires tightly controlled conditions to prevent contamination. (Sisse Brimberg and Cotton Coulson)
Meanwhile, Jenkins went back to his day job as an archaeologist at the Oregon State Museum of Natural and Cultural History. Almost two years passed, and by the summer of 2006 Jenkins had almost forgotten the whole DNA business. Then one morning he received an e-mail from Willerslev. The Dane wanted to know how old the Paisley coprolites were.
In his lab in Copenhagen, Willerslev and a colleague had come up with stunning results. Six of the turds contained undeniably human DNA. Not only that, they bore certain genetic markers found only in Native American populations. Willerslev agreed to pay labs in Oxford and Florida to radiocarbon date each coprolite.
The results, Jenkins says, were "earth-shaking." Both labs agreed that the coprolites were left 14,300 years ago--almost 1,500 years before the earliest agreed-upon evidence for human presence in the Americas. "For the first time, we are actually radio-carbon dating human remains that are pre-Clovis," Jenkins says. "There are older radiocarbon dates on sites in North America, but not directly on human remains."
The find's implications are tremendous. For almost a century, archaeologists believed that people arrived in North America 13,000 years ago--a conclusion based on dating sites with a distinctive stone tool type first found near Clovis, New Mexico in the 1930s. For the last two decades, the "Clovis-first" idea has been under steady assault. Call it revisionist prehistory: researchers have turned up evidence they say supports everything from a much earlier migration from Asia to a sea-borne invasion from Europe.
The coprolites Jenkins found in the Paisley caves may well be the final nail in Clovis' coffin. While other supposed pre-Clovis sites have been bogged down in arguments over whether stone tools were made by people or by accident, there's no doubt who made the coprolites Jenkins found in the Paisley cave. "It's a much more compelling case than this odd-looking rock found next to that piece of charcoal. We know a human made this turd, whereas we don't know if that was a campfire," says Southern Methodist University archaeologist David Meltzer. "The pre-Clovis genie is sort of out of the bottle, and there's no way of stuffing it back in."
Contributing editor Andrew Curry is based in Berlin, Germany.
© 2008 by the Archaeological Institute of America