Top Stories - Posted by Jim Barlow-Oregon on Friday, July 13, 2012 11:04 - 2 Comments
Darts raise doubts about who was first to America
U. OREGON (US) — Stone darts and DNA from ancient feces found in Oregon’s Paisley Caves suggest the Clovis were not the first people to live in North America.
The Western Stemmed projectile points—darts or thrusting spearheads—the researchers discovered were present at least 13,200 calendar years ago during or before the Clovis culture in western North America.
Absent from the Paisley Caves, says the project’s lead researcher Dennis L. Jenkins of the Museum of Natural and Cultural History at the University of Oregon, is diagnostic evidence of the Clovis culture such as the broad, concave-based, fluted Clovis projectile points.
Dennis Jenkins with a human coprolite (dried feces) found in Oregon’s Paisley Caves. (Credit: Jim Barlow)
Sealed sample of human coprolite. (Credit: University of Oregon)
Straight from the Source
“Through replicating data we were able to confirm the authenticity of what is the oldest direct evidence for humans in the Americas,” says study co-author Michael “Michi” Hofreiter, a biologist in DNA laboratory of the University of York in the United Kingdom. “The results of this study are exciting, because they show that the hypothesis that the Clovis people were the first Native Americans, which has been the prevailing idea for the last decades, is wrong. Now researchers need to come up with a new model for the settling of the Americas.”
In a paper in the July 13 issue of Science, researchers from 13 institutions lay out their findings, which also include substantial new documentation, including “blind-test analysis” by independent labs, that confirms the human DNA pulled earlier from human coprolites (dried feces) and reported in Science (May 9, 2008) dates to the same time period.
The new conclusions are based on 190 radiocarbon dates of artifacts, coprolites, bones, and sagebrush twigs meticulously removed from well-stratified layers of silt in the ancient caves.
The radiocarbon dating of the Western Stemmed projectiles to potentially pre-Clovis times, Jenkins says, provides new information in the decades-old debate that the two point-production technologies overlapped in time and may have developed separately. It suggests that Clovis may have arisen in the Southeastern United States and moved west, while the Western Stemmed tradition began, perhaps earlier, in the West and moved east.
One example, he says, is the discovery of Clovis points below Western Stemmed points at Hell Gap, Wyoming. While this example suggests that Clovis was older in that location than Western Stemmed, the new Paisley Caves evidence indicates that Western Stemmed are at least the same age as Clovis (about 12,800-13,000 years old) in the northern Great Basin of Oregon—about 1,000 miles west of Hell Gap.
At least three other Western sites—Cooper’s Ferry in Idaho and Nevada’s Smith Creek Cave and Bonneville Estates Rockshelter—also contain only Western Stemmed points in deposits of this age.
“From our dating, it appears to be impossible to derive Western Stemmed points from a proto-Clovis tradition,” Jenkins says. “It suggests that we may have here in the Western United States a tradition that is at least as old as Clovis, and quite possibly older. We seem to have two different traditions co-existing in the United States that did not blend for a period of hundreds of years.”
Follow the kelp highway
The origin of humans in the Americas has long suggested early migration out of Siberia and eastern Asia, very possibly across a temporary land bridge between Russia and Alaska.
In more recent years, Jenkins’ colleague, Jon Erlandson, has been building evidence—a lot of it emerging from the Channel Islands off California—of a Late Pleistocene sea-going people following a “kelp highway” from Japan to Kamchatka, along the south coast of Beringia and Alaska, then southward down the Northwest Coast to California. Kelp forests are rich in seals, sea otters, fish, seabirds, and shellfish such as abalones and sea urchins.
The new paper doesn’t address the routes early migrants may have taken, but the additional evidence found in the DNA of the coprolites continues to point to Siberia-east Asian origins. Again, as in 2008, the human mitochondrial DNA—passed on maternally—was from haplogroup A, which is common to Siberia and found, along with haplogroup B, in Native Americans today.
DNA cannot be directly dated with radiocarbon technology. Instead, researchers extracted components of the diet eaten by the early inhabitants and washed potentially contaminating carbon out of the coprolites with distilled water. The digested fibers and carbon fraction were then radiocarbon-dated separately and the results compared.
The only significant aging difference in 12 such tests involved a camelid (ice-age llama) coprolite that was dated through its contents to about 14,150 years ago, while its water-soluble extract was dated to 13,200 years ago. This sample was found below a mud lens that contained one of the Western Stemmed points and human coprolites dated to between 13,000 and 13,200 years ago.
The meticulous methodology used, Jenkins says, was done to address criticism that the 2008 findings may have been compromised by contamination, such as the leaching of later DNA from humans by water and rodent urine downward through the caves’ many layers. The new evidence indicates this form of contamination is not a good explanation for the pre-Clovis human DNA.
“We continued to excavate Paisley Caves from 2009 through 2011,” the authors wrote in Science. “To resolve the question of stratigraphic integrity, we acquired 121 new AMS [accelerator mass spectrometry] radiocarbon dates on samples of terrestrial plants, macrofossils from coprolites, bone collagen, and water soluble extracts recovered from each of these categories. To date, a total of 190 radiocarbon dates have been produced from the Paisley Caves.”
The Paisley Caves are in the Summer Lake basin near Paisley, about 220 miles southeast of Eugene on the east side of the Cascade Range. The complex includes eight westward-facing caves, all wave-cut shelters, on the highest shoreline of pluvial Lake Chewaucan, which rose and fell in periods of greater precipitation during the Pleistocene, or last glacial period.
“Following the recession of lake waters, the caves began to accumulate different kinds of terrestrial sediments,” says co-author Loren Davis, an archaeologist at Oregon State University in Corvallis. “The caves contain a series of deposits that were created by the combination of wind, gravity, water-borne and biological processes.
“Archaeological evidence suggests that humans visited the cave many times, leaving behind material traces in the form of stone tools, lithic chipping debris, organic craft items, food wastes, and even coprolites. These cultural materials were entombed largely as they were left behind as sediments continued to accumulate.”
The National Science Foundation, Danish Research Foundation, US Bureau of Land Management, UO archaeological field school, UO Museum of Natural and Cultural History, Oregon State University Keystone Archaeological Research Fund, Bernice Peltier Huber Charitable Trust, and University of Nevada, Reno, Great Basin Paleoindian Research Unit were primary funders of the fieldwork.
More news from the University of Oregon: http://uonews.uoregon.edu/