For
many years, scientists have thought that the first Americans came here
from Asia 13,000 years ago, during the last ice age, probably by way of
the Bering Strait. They were known as the Clovis people, after the town
in New Mexico where their finely wrought spear points were first
discovered in 1929.
But
in more recent years, archaeologists have found more and more traces of
even earlier people with a less refined technology inhabiting North
America and spreading as far south as Chile.
And
now clinching evidence in the mystery of the early peopling of America —
Clovis or pre-Clovis? — for nearly all scientists appears to have
turned up at a creek valley in the hill country of what is today Central
Texas, 40 miles northwest of Austin.
The
new findings establish that the last major human migration, into the
Americas, began earlier than once thought. And the discovery could
change thinking about how people got here (by coastal migrations along
shores and in boats) and how they adapted to the new environment in part
by making improvements in toolmaking that led eventually to the
technology associated with the Clovis culture.
Archaeologists and other scientists report in Friday’s issue of the journal Science
that excavations show hunter-gatherers were living at the Buttermilk
Creek site and making projectile points, blades, choppers and other
tools from local chert for a long time, possibly as early as 15,500
years ago. More than 50 well-formed artifacts as well as hundreds of
flakes and fragments of chipping debris were embedded in thick clay
sediments immediately beneath typical Clovis material.
“This
is the oldest credible archaeological site in North America,” Michael
R. Waters, leader of the discovery team, said at a news teleconference.
Dr.
Waters, director of the Center for the Study of the First Americans at
Texas A&M University, and his colleagues concluded in the journal
article that their research over the last six years “confirms the
emerging view that people occupied the Americas before Clovis and
provides a large artifact assemblage to explore Clovis origins.”
If
the migrations began at earlier, pre-Clovis times, moreover, extensive
glaciers probably closed off ice-free interior corridors for travel to
the warmer south. Archaeologists said this lent credence to a fairly new
idea in the speculative mix: perhaps the people came to the then really
new New World by a coastal route, trooping along the shore and
sometimes hugging land in small boats. This might account for the
relatively swift movement of the migrants all the way to Peru and Chile.
The
first of the distinctive Clovis projectile points represented advanced
skills in stone technology. About a third of the way up from the base of
the point, the artisans chipped out shallow grooves, called flutes, on
both faces. The bifacial grooves probably permitted the points to be
fastened to a wooden spear or dart.
Other
archaeologists pointed out that the Buttermilk Creek dates, more than
2,000 years earlier than the Clovis chronology, are not significantly
older than those for other sites challenging the Clovis-first
hypothesis. In recent years, early human occupation sites have been
examined coast to coast: from Oregon to Wisconsin to western
Pennsylvania and from Maryland and Virginia down to South Carolina and
Florida.
James M. Adovasio, an archaeologist who found what appears to be pre-Clovis material at the Pennsylvania site known as Meadowcroft Rockshelter,
was not involved in the Buttermilk Creek excavations but has visited
the site and inspected many of the artifacts. These pre-Clovis
projectile points were also bifacial but not as large and well turned as
the later technology. The most striking difference was the absence of
the characteristic fluting.
Dr.
Adovasio, a professor at Mercyhurst College in Erie, Pa., said some of
the Buttermilk Creek material resembled tools at his site and others at
Cactus Hill, Va., and Miles Point, Md.
“It
would appear the assemblage of artifacts is enough different from
typical Clovis to be a distinct technology,” Dr. Adovasio said in an
interview. “But it is not as much different as not to be ancestral to
Clovis material.”
That
is another likely implication of the new findings, also noted by Dr.
Waters and his team. It would appear that the Clovis technology was not
an Asian import; it was invented here.
No
one knows exactly who these migrating people were, scientists said.
Genetic studies of ancient bones and later American Indians indicate
their ancestors came from northeast Asia, possibly across the Bering
land bridge at a time of low sea levels during the last ice age. But it
has puzzled scientists that nothing like the Clovis technology has ever
been found in Siberia.
The
new findings, the Waters group reported, “suggest that although the
ultimate ancestors of Clovis originated from northeast Asia, important
technological developments, including the invention of the Clovis fluted
points, took place south of the North American continental ice sheets
before 13,100 years ago from an ancestral pre-Clovis tool assemblage.”
Among
other implications of the discoveries, the Texas archaeologists said, a
pre-Clovis occupation of North America provided more time for people to
settle in North America, colonize South America by more than 14,000
years ago, “develop the Clovis tool kit and create a base population
through which Clovis technology could spread.”
The
Texas archaeologists said the new dig site has produced the largest
number of artifacts dating to the pre-Clovis period. The dates for the
sediments bearing the stone tools were determined to range from 13,200
to 15,500 years ago.
Given
the lack of sufficient organic material buried around the tools, the
radiocarbon dating method was useless. Instead, earth scientists at the
University of Illinois, Chicago, used a newer technique known as
optically stimulated luminescence. This measures light energy trapped in
minerals to reveal how long ago the soil was last exposed to sunlight.
Steven
L. Forman, who directed the tests, said that 49 core samples were
drilled from several sections of the sediments associated with the
tools. When the data were analyzed, they consistently yielded the same
ages. “This was unequivocal proof of pre-Clovis,” he said at the news
conference.
Other
scientists examined the flood plain geology at the site and determined
that the clay sediments showed virtually no sign of having been
disturbed during or after the burying of the tools. Lee C. Nordt, a
geology professor at Baylor University, said that the traces of previous
cracks in the sediment were few and too narrow to have allowed more
recent artifacts from above to have settled into the deeper pre-Clovis
layers.
Until
recently, Dr. Waters said, archaeologists had probably overlooked
earlier artifacts because the Clovis points are so distinctive and, in
contrast, the pre-Clovis material has no hallmark style calling
attention to itself.
“Finally, we are able to put Clovis-first behind us and move on,” he said.
A
few scientists, even among those who endorse the presence in the
Americas, said they had some reservations about aspects of excavation
methods at the Texas site. One who did not want to be quoted or
identified questioned whether the reported artifacts justified such a
fanfare. He considered the whole issue settled years ago when a panel of
experts judged that the Monte Verde site in southern Chile was indeed
pre-Clovis.
Dr.
Adovasio noted that the Clovis model had been “dying a slow death.” He
recalled that “Waters himself was a Clovis-firster, but changed years
ago.” At a conference in 1999, the conventional hypothesis seemed to be
on its last legs after a review of the Monte Verde data; still a few
holdouts stood fast in opposition.
“The last spear carriers will die without changing their minds,” Dr. Adovasio said.
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