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Friday, July 27, 2012
As readers of this blog know, I have championed two separate and
plausibly near simultaneous coastal penetrations of the Americas as
early even as twenty thousand years ago. We have scant support yet
for the twenty thousand year figure, but I prefer as early a date as
possible. It is completely possible that the expansion largely
followed coastlines for several thousands of years before population
pressures caused significant adaptation to more interior conditions.
The Clovis point is surely such an adaptation since it lacks an
equivalent in the Old world.
After the Pleistocene nonconformity which destroyed Clovis culture,
it is likely North America was repopulated from the South initially
and from Alaska much later as the ice barrier receded. We also have
later European genetics in the North East likely from the European
bronze Age impact.
What we have learned is that Clovis was not unique and that the story
of North American Prehistory is far from simple.
It is always reassuring to stake out my ground and watch the
scholarship slowly confirm the model, hopefully with serious
Caves as old as Clovis sites - but not Clovis
A new study of
Oregon's Paisley Caves confirms that humans used the site as early as
12,450 radiocarbon years ago, and the projectile points they left
behind were of the "Western Stemmed" tradition and not
Clovis - which suggests parallel technological development of early
inhabitants to the Americas. The study, published this week in the
journal Science, could have a major impact on theories of how the
Western Hemisphere was populated.
The research was
funded by multiple organizations, including the National Science
author Dennis Jenkins, from the University of Oregon, and second
author Loren Davis, from Oregon State University, were part of a
large multidisciplinary team that spent much of the past two years
combing through deposits and collecting more than 100
high-precision radiocarbon dates from Paisley Caves,
located in south-central Oregon's Summer Lake basin.
What cemented the
authors' findings was a thorough examination of the stratigraphy in
the caves, which confirmed that coprolites containing human DNA
were definitely associated with layers of sediment ranging in age
from 2,295 to 12,450 years ago - and were not contaminated by
humans or animals at later dates. The researchers last year also
found additional Western Stemmed projectile points.
Western Stemmed and Clovis traditions include different technological
strategies," said Davis, an associate professor
of anthropology in OSU's School of Language, Culture and
Stemmed artifacts from Paisley Caves are at least as old - and may
predate - the oldest confirmed Clovis sites, indicating that the
peopling of the Americas was at least technologically divergent, if
not genetically divergent."
The projectile points
were found in deposits dating back to 11,070 to 11,340 radiocarbon
years ago, and thus were not quite as old as the oldest coprolites.
But DNA from coprolites of that era was similar to that found in the
oldest coprolites, Davis pointed out. "They were from the same
genetic group," he said.
The difference in
technology between Clovis and Western Stemmed projectile points
revolves around how they were attached to spears, which relates to
the strategy of finding and shaping pieces of rock in the first
place. Clovis artifacts have a distinct notch at the base, where a
piece has been removed. The tool builder starts with a large rock and
reduces it considerably.
Western Stemmed points
and Clovis points primarily differ in the construction of their
hafting portions, Davis said. Stemmed points bear constricted bases,
while the hafting element of a Clovis point is thinned through the
removal of a large flake from the base. Western Stemmed points are
also often made by modifying smaller flakes in a different way than
Clovis peoples manufactured their spear points.
approaches to making projectile points were really quite different,"
Davis said, "and the fact that Western Stemmed point-makers
fully overlap, or even pre-date Clovis point makers likely means that
Clovis peoples were not the sole founding population of the
technology has only been found in the New World, while Western
Stemmed technology can be related to archaeological patterns
seen in northeastern Asia.
"We seem to have
two different traditions co-existing in the United States that did
not blend for a period of hundreds of years," said the
University of Oregon's Jenkins.
studies of Paisley Caves also have reported on human coprolites with
ancient DNA, but questions arose about whether those samples
could have been contaminated, and whether they were found in context
with artifacts from the same era. So the researchers did an
exhaustive examination of the stratigraphy, which is one of Davis'
microscopic analysis of the soil structure using a petrographic
microscope to eliminate signs of liquid - such as water or urine from
humans or animals - moving downward through the soil. The team also
carefully analyzed the silt lens where the stem points were found and
bracketed above and below those layers to see if radiocarbon dates
points were in great context," Davis said. "There is no
doubt that they were in primary context, associated with excellent
earliest models for peopling of the Americas suggest that the first
inhabitants arrived from Asia via a land bridge at the end of
the last Ice Ageand fanned out across the continent.
However, those models can't explain the presence of two separate and
distinct stone tool technologies at the end of the last glacial
recent results from Paisley Caves, it's clear that we need to come up
with some better models," Davis said.