New artifacts suggest
people arrived in North America earlier than previously thought
Oregon State University – August 30,
2019 -- Stone tools and other artifacts unearthed from an archeological dig at
the Cooper's Ferry site in western Idaho suggest that people lived in the area
16,000 years ago, more than a thousand years earlier than scientists previously
thought.
The artifacts would be considered among
the earliest evidence of people in North America.
The findings, published today in Science,
add weight to the hypothesis that initial human migration to the Americas
followed a Pacific coastal route rather than through the opening of an inland
ice-free corridor, said Loren Davis, a professor of anthropology at Oregon
State University and the study's
lead author.
"The Cooper's Ferry site is located
along the Salmon River, which is a tributary of the larger Columbia River
basin. Early peoples moving south along the Pacific coast would have encountered
the Columbia River as the first place below the glaciers where they could
easily walk and paddle in to North America," Davis said.
"Essentially, the Columbia River corridor was the first off-ramp of a
Pacific coast migration route.
"The timing and position of the
Cooper's Ferry site is consistent with and most easily explained as the result
of an early Pacific coastal migration."
Cooper's Ferry, located at the
confluence of Rock Creek and the lower Salmon River, is known by the Nez Perce
Tribe as an ancient village site named Nipéhe. Today the site is managed by the
U.S. Bureau of Land Management.
Davis first began studying Cooper's
Ferry as an archaeologist for the BLM in the 1990s. After joining the Oregon
State faculty, he partnered with the BLM to establish a summer archaeological
field school there, bringing undergraduate and graduate students from Oregon
State and elsewhere for eight weeks each summer from 2009 to 2018 to help with
the research.
The site includes two dig areas; the
published findings are about artifacts found in area A. In the lower part of
that area, researchers uncovered several hundred artifacts, including stone
tools; charcoal; fire-cracked rock; and bone fragments likely from medium- to
large-bodied animals, Davis said. They also found evidence of a fire hearth, a
food processing station and other pits created as part of domestic activities
at the site.
Over the last two summers, the team of
students and researchers reached the lower layers of the site, which, as
expected, contained some of the oldest artifacts uncovered, Davis said. He
worked with a team of researchers at Oxford University, who were able to
successfully radiocarbon date a number of the animal bone fragments.
The results showed many artifacts from
the lowest layers are associated with dates in the range of 15,000 to 16,000
years old.
"Prior to getting these radiocarbon
ages, the oldest things we'd found dated mostly in the 13,000-year range, and
the earliest evidence of people in the Americas had been dated to just before
14,000 years old in a handful of other sites," Davis said. "When I
first saw that the lower archaeological layer contained radiocarbon ages older
than 14,000 years, I was stunned but skeptical and needed to see those numbers
repeated over and over just to be sure they're right. So we ran more
radiocarbon dates, and the lower layer consistently dated between 14,000-16,000
years old."
The dates from the oldest artifacts
challenge the long-held "Clovis First" theory of early migration to
the Americas, which suggested that people crossed from Siberia into North
America and traveled down through an opening in the ice sheet near the present-day
Dakotas. The ice-free corridor is hypothesized to have opened as early as
14,800 years ago, well after the date of the oldest artifacts found at Cooper's
Ferry, Davis said.
"Now we have good evidence that
people were in Idaho before that corridor opened," he said. "This
evidence leads us to conclude that early peoples moved south of continental ice
sheets along the Pacific coast."
Davis's team also found tooth fragments
from an extinct form of horse known to have lived in North America at the end
of the last glacial period. These tooth fragments, along with the radiocarbon
dating, show that Cooper's Ferry is the oldest radiocarbon-dated site in North
America that includes artifacts associated with the bones of extinct animals,
Davis said.
The oldest artifacts uncovered at
Cooper's Ferry also are very similar in form to older artifacts found in
northeastern Asia, and particularly, Japan, Davis said. He is now collaborating
with Japanese researchers to do further comparisons of artifacts from Japan,
Russia and Cooper's Ferry. He is also awaiting carbon-dating information from
artifacts from a second dig location at the Cooper's Ferry site.
"We have 10 years' worth of
excavated artifacts and samples to analyze," Davis said. "We
anticipate we'll make other exciting discoveries as we continue to study the
artifacts and samples from our excavations."
Co-authors of the paper include David
Sisson, an archaeologist with the BLM; David Madsen of the University of Texas
at Austin; Lorena Becerra Valdivia and Thomas Higham of the Oxford University
radiocarbon accelerator unit; and other researchers in the U.S., Japan and
Canada. The research was funded in part by the Keystone Archaeological Research
Fund and the Bernice Peltier Huber Charitable Trust.
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