How and when humans originally came to North America is one of the most
hotly debated topics in archaeology. The conventional view among
archaeologists is that around 13,000 years ago, a transient opening between
ice sheets allowed humans to pass via a corridor free of ice.
However, an increasing amount of genetic and archeological evidence, such
as human footprints discovered in New Mexico that date to around 23,000
years ago, indicates that humans arrived on the continent far earlier. These
early Americans most likely came from Beringia, the land bridge that
connects Asia and North America and developed during the last glacial
maximum, when ice sheets held up vast quantities of water, lowering sea
levels. They journeyed down the Pacific coastline.
Sea ice may have been one means for humans to migrate farther south,
according to
research that will be presented
on Friday, December 15 at the
American Geophysical Union Annual Meeting (AGU23)
in San Francisco. Paleoclimate reconstructions of the Pacific Northwest
suggest this.
It's not a novel notion that prehistoric Americans may have journeyed
around the Pacific Coast. At least 16,000 years ago, much of the continent
was covered by enormous ice sheets, which is presumably where people were
living at the time.
Rather than the ice-free route, which would have been closed off for
thousands of years prior to these early settlers, scientists suggested that
people may have migrated over a "kelp highway." According to this idea,
early Americans gradually migrated southward into North America on boats,
pursuing the abundant resources found in coastal seas.
In western Canada, archaeologists have discovered evidence of coastal
communities as early as 14,000 years ago. However, in 2020, scientists found
that it could have been difficult for humans to go along the shore due to a
strong current caused by freshwater from melting glaciers at the time.
Over hazardous water, an ice highway
In order to obtain a more comprehensive understanding of the oceanic
conditions throughout these significant periods of human migration, Summer
Praetorius and her colleagues examined climate proxies found in coastal
ocean sediment. Tiny, petrified plankton provided the majority of the data.
These species' chemistry and abundance aid in the reconstruction of sea ice
cover, salinity, and ocean temperatures.
At AGU23, Praetorious will be speaking as part of a
session
on the geology and climatic history of Beringia and the North Pacific during
the Pleistocene, or modern ice age. This year, the week-long conference
united 3,000 online attendees and attracted 24,000 professionals from many
fields in Earth and space sciences to San Francisco.
Using climate models, Praetorious' team discovered that, at the height of
the last glacial maximum, some 20,000 years ago, ocean currents were more
than twice as strong as they are now because of glacial winds and lower sea
levels. These circumstances would have made boat passage extremely
difficult, if not impossible to paddle against, according to
Praetorius.
But the data also revealed that until around 15,000 years ago, a large
portion of the region was covered in sea ice throughout the winter.
Praetorius speculated that since they were a cold-adapted tribe, "perhaps
they were using the sea ice as a platform rather than having to paddle
against this horrible glacial current."
These days, people in the Arctic use dog sleds and snowmobiles to traverse
the sea ice. According to Praetorius, early Americans could have traveled
along the "sea ice highway" to hunt marine animals and gradually make their
way into North America. The climatic data indicate that between 24,500 and
22,000 years ago and 16,400–14,800 years ago, the coastal route may have
supported migration, maybe with the help of winter sea ice.
The proposal offers a fresh framework for understanding how humans may have
arrived in North America without the need for an easy way over the ocean or
a land bridge, even if it will be difficult to prove that people were
utilizing sea ice for transportation given that the majority of the
archeological sites are underwater.
Furthermore, according to Praetorius, the sea ice corridor doesn't preclude
future human migrations. According to the team's models, 14,000 years ago
the Alaskan current had subsided, facilitating simpler boat passage down the
coast.
She declared, "Nothing is off the table." "We will always be surprised by
ancient human ingenuity."
Provided by
American Geophysical Union
