When did the Bering Land Bridge become the Bering Strait? When and
how did the first Americans cross from Asia? Questions like these
have stirred controversy in the decades since the discovery of Clovis
man. The findings of human settlements as far south as Monte Verde,
Chile, around 14,500 years ago, had already generated new theories
from archeologists. One idea was that people may have migrated into
North America by boat along what would have been the southern coast
of the Bering Land Bridge.
Now Scripps Institution of Oceanography Geosciences Professor
Neal Driscoll and his collaborators at Woods Hole Oceanographic
Institution
and the University of Massachusetts-Amherst have found evidence
that the actual land bridge in the Bering Strait near Alaska
flooded into
the Arctic Ocean about 12,000 years ago, roughly 1,000 years later
than widely thought, closing off the land bridge thought to be
used for human migration. Finding proof to make this type of statement proved challenging
to earlier researchers because sediment cores collected on
the Chukchi
Shelf bordering the Arctic Ocean had failed to provide enough historical
information about climate change, sea-level rise and related events.
That problem began to be resolved in 2002 when Driscoll and his
colleagues extracted cores from previously untapped locations
north and west
of Alaska in the Chukchi Sea. The Sea, bordering the Arctic Ocean,
covers part of the continental shelf exposed when sea level fell
during the last glacial maximum, about 20,000 years ago. The cores were examined for skeletons of animals called foraminifera,
which are used to identify specific water and atmospheric temperatures.
The layers of accumulated sediment in the cores provided a “high
resolution” picture more than 100 times more detailed than
previous cores, helping to open the door to new ideas about the ocean
and climate histories of the region. And that in turn has opened the door for new interpretations
of human migration into North America. 
— Mario Aguilera, ’89
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