12 April 2008
Researchers find pre-Clovis human DNA
Human DNA from dried excrement recovered from Oregon's Paisley Caves (USA) is the oldest found yet in the New World - dating to 14,300 years ago, some 1,200 years before Clovis culture - and provides apparent genetic ties to Siberia or Asia, according to an international team of 13 scientists. The Paisley Caves are located in the Summer Lake basin near Paisley, about 220 miles southeast of Eugene on the eastern side of the Cascade Range. The series of eight caves are westward-facing, wave-cut shelters on the highest shoreline of pluvial Lake Chewaucan.
The teamís extensively documented analyses on mitochondrial DNA - genetic material passed on maternally - removed from long-dried feces, known as coprolites, were published online April 3 in Science Express ahead of regular publication in the journal Science. "The Paisley Cave material represents, to the best of my knowledge, the oldest human DNA obtained from the Americas," said Eske Willerslev, director of the Centre for Ancient Genetics at Denmark's University of Copenhagen. "Other pre-Clovis sites have been claimed, but no human DNA has been obtained, mostly because no human organic material had been recovered."
A Danish team, led by Willerslev, examined 14 coprolites that were found by s L. Jenkins, a senior archaeologist with the University of Oregonís Museum of Natural and Cultural History, during summer field work in 2002 and 2003. A lengthy analysis was done to screen for modern DNA contamination. From that analysis, six coprolites containing the ancient DNA were radiocarbon dated using accelerator mass spectrometry. With radiocarbon dating adjusted to calendar years, the materials date back to about 14,300 years ago. The DNA testing indicated that the feces belonged to Native Americans in haplogroups A2 and B2, haplogroups common in Siberia and east Asia.
Clovis culture began sometime between 13,200 and 12,900 years ago, according to a re-evaluation of Clovis evidence published in Science (Feb. 23, 2008) by Michael R. Waters of Texas A&M University and Thomas W. Stafford Jr. of Stafford Research Laboratories in Colorado. Skeletal remains dating to Clovis culture have proven elusive, leaving researchers with little hard evidence beyond tell-tale cultural components such as the distinctive fluted Clovis points and other tools.
In their conclusion, the authors wrote: "The Paisley Caves lack lithic tool assemblages, thus the cultural and technological association of the early site occupants, and their relationship to the later Clovis technology are uncertain. We are not saying that these people were of a particular ethnic group. At this point, we know they most likely came from Siberia or Eastern Asia, and we know something about what they were eating, which is something we can learn from coprolites." "If our DNA evidence and radiocarbon dating hold up on additional coprolites that are now undergoing testing at multiple labs, then we have broken the Clovis sound barrier, if you will," he said. "If you are looking for the first people in North America, you are going to have to step back more than 1,000 years beyond Clovis to find them."
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, and the coprolites Jenkins found in the Paisley caves may well be the final nail in Clovis' coffin.
Sources: News Wise (2 April 2008), Archaeology.org (3 April 2008)