The Beringland Bridge, which once connected Asia with Alaska, may have emerged much later than previously thought, narrowing the window of time humans moved to America.
The land bridge may exist around 35,000 years ago, and new research has discovered before the coldest part of the last ice age known as the Last Ice Age (LGM). This is the Jive, one of the oldest and most well-established locations of human activity in the Americas. These are footprints from 23,000 years ago found in White Sands National Park in New Mexico.
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Ice Age Cycle
The Earth undergoes a cycle in which, more or less, ice covers the world’s surfaces on a regular basis. At each ice age, the world’s sea level drops as the planet’s water freezes in the enormous ice sheet. At the end of these ice times, as temperatures rise, the ice sheet melts and sea levels rise.
Previous studies have found that in LGM, the Beringland Bridge allows animals such as mammoths and horses to roam between Asia and America. A better understanding of the recent land bridges above sea level may help to clarify when and how humans have migrated to the New World.
Previous studies suggested that global sea level levels were approximately 425 feet (130 meters) lower at LGMs from 26, 500 to 19,000 years ago. Jesse Farmer, an assistant professor at the University of Massachusetts’ School of Environment at Boston and co-author of a new study on land bridges, spoke to Live Science. This led scientists to estimate that Beringland Bridge is above sea level about 70,000 years ago, he noted.
However, there were probably two indications that there were still more indications in the big picture of Beringland Bridge. First, “Even back then, you can’t know the sea level very accurately,” Farmer said. “An uncertainty of about 10-20 meters (33-66 feet) would be very good with existing tools.”
Second, “In this case, we are not interested in the Bering Strait, specifically,” Farmer said. Higher latitudes such as where the Bering Strait were located were relatively close to where the ice sheets were growing. The weight of the ice would have pushed down the land and raised the local sea level.
In fact, in a 2023 PNAS paper, the farmer and his colleagues revealed that Beringland Bridge may have actually been flooded for 46,000 to 35,700 years ago. Marine sediment data suggest that nutrients typical of the Pacific began to invade the Arctic Ocean during that time, most likely the Bering Strait was open.
These findings suggest that Beringland Bridge may have only resumed about 10,000 years, the height of the last ice age, much later than previously thought. One of the questions that helps this address is which human lineage (our humans or our extinct relatives) traveled to the New World.
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“The late emergence would support the idea that a completely modern man first traveled to the North American continent,” Ian Boutitt, an independent archaeologist who did not participate in the study, told Live Science. “The Neanderthals and Denisovan, the other human races known to have occupied parts of Siberia, were at risk of extinction across Northeast Asia by this point.”
Furthermore, analysis of fossils of ancient animals up to 46,000 years ago in both Eurasia and America, including mammoths, bisons, lions, and bears, supported the possibility that the Beringland Bridge may be open later than previously thought. A computer model of the migration of these creatures based on fossil deposits suggested that the overpass was closed during the span suggested by a 2023 paper.
“We have two completely different datasets that tell the same story,” Farmer said.
While the Bellingland Bridge may not have been open late than previously thought, Farmer said the knowledge of the sailors shown by modern Inuit ancestors suggests that ancient humans could head to America by boat, just as ancient humans migrated to Australia and the new Guinea.
“The migration of humans to America 40,000-35,000 years ago required the ability to navigate ships and the open ocean,” Buvit said. “As far as we know, this was accomplished anatomically only by modern humans.”
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