The theory of a land bridge has fueled the imagination of explorers and scientists for centuries. The existence of land connections between continents has significant implications for understanding the migration of animals and humans across the globe. Recent geological discoveries and studies have shed light on the existence of such land bridges, particularly between Africa and Asia, and their role in shaping the distribution of species.
A map of how Beringia - which includes the famous ice age land bridge - possibly looked about 18,000 years ago.
The Bering Land Bridge: A Testament to Past Connections
During the coldest part of the last ice age, between about 26,500 and 19,000 years ago, global sea levels were about 425 feet (130 m) lower. The resulting Bering Land Bridge let animals such as mammoths and horses roam between Asia and the Americas.
The Bering Strait is a 52-mile-wide (85 kilometers), 165-foot-deep (50 meters) stretch of water between Alaska and Siberia. Today, it divides North America and Asia. However, during the coldest part of the last ice age between about 26,500 and 19,000 years ago, as the planet's water became frozen in massive ice sheets, global sea levels were about 425 feet (130 m) lower.
The resulting Bering Land Bridge let animals such as mammoths and horses roam between Asia and the Americas.
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Much remains debated about whether and how humans used the Bering Land Bridge to migrate to the New World. For instance, a 2022 study found that this strip of land may have been blocked by an icy barrier by the time humans could have come to it. As such, the first people in the Americas may have boated or walked along the bridge's coast instead of trekking across its interior on foot.
Exploring the buried Bering Land Bridge would be exceedingly difficult and costly, but the archaeological payoff could be extraordinary, experts told Live Science.
Ideally, scientists would dig into the Bering seafloor to find signs of ancient human migrants. "We have only a handful of archaeological sites in this area from the end of the ice age, so literally any site we find could completely change what we know about these early people," Jessi Halligan, an underwater archaeologist at Texas A&M University, told Live Science.
The chances are high that human sites and human remains could survive after millennia underwater. Because of the cold water of the Bering Strait, "any animals, clothing fragments, housing bits, charcoal, or other organic remains the people left behind are much more likely to have preserved because the cold water has fewer microbes to destroy them than can be found in open air or warmer water," Halligan said. "These sites could potentially be almost pristine."
However, actually making such discoveries in the Bering Strait "is a monumental challenge," Morgan Smith, director of the geoarchaeology and submerged landscapes lab at the University of Tennessee, Chattanooga, told Live Science. "The conditions there can become super-unmanageable super-fast."
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The remote location of the Bering Strait also makes expeditions there expensive. "You need huge research vessels to go there, and those can cost $8,000 to $15,000 a day, not including fuel," Smith said. "These are really busy boats, so you have to reserve them a year in advance; you can't predict weather even 10 days in advance, so you have to hope that you don't have bad luck during your trip."
All in all, Bering seafloor research would "take time and money, but the outcomes could be extremely exciting," Halligan said.
During the periodic ice ages over Earth’s history, global sea levels drop as more and more of Earth’s water becomes locked up in massive ice sheets. At the end of each ice age, as temperatures increase, ice sheets melt and sea levels rise.
During the last ice age’s peak, known as the Last Glacial Maximum, the low sea levels exposed a vast land area that extended between Siberia and Alaska known as Beringia, which included the Bering Land Bridge.
But the new data show that sea levels became low enough for the land bridge to appear only 35,700 years ago.
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“It’s generally believed that the land bridge was open for a while, and then humans crossed it at some point,” Sigman said.
The researchers noted that they need to be cautious when considering these implications, as the interpretation requires combining very different types of information, including the new data and the information of human geneticists and paleoanthropologists.
Balkanatolia: A Lost Continent Connecting Continents
Scientists claim to have discovered a long-forgotten continent that once connected Europe, Africa, and Asia and served as a passage for the animals’ migration. Maps show the “lost” continent, dubbed Balkanatolia, 40 million years ago and today. In the period known as the Eocene, 55 to 34 million years ago, the European and Asian continents existed as distinct land masses with their own unique mammal families, among them rodents, ungulates, and other now extinct species.
The "lost" continent, dubbed Balkanatolia, 40 million years ago and today.
But the traditional understanding of how these two land masses became one, and the timing of Asian mammals’ eventual arrival in Western Europe, has largely remained a mystery.
An event known as the “Grande Coupure” has been the leading hypothesis explaining the extinction of native European fauna and the arrival of species from Asia.
The researchers examined fossils found in the Balkans dating from the Eocene period that further lend to the theory of an earlier arrival of some species into southern Europe. They also found new fossil deposits in Büyükteflek in central Anatolia that support the existence of an independent land mass characterized by the presence of mammal species distinct from those of both Europe and Asia.
This third continent, Balkanatolia, created a pathway for Eurasian migration much earlier in the Eocene period than previously understood.
“Existing data show that [Balkanatolia] acted as a crossroads between Asia, Europe and Africa, while keeping a unique fauna for millions of years,” Licht said in a statement.
The arrival of Asian mammals 41 to 38 million years ago would eventually lead to the extinction of Balkanatolian mammal species, the result of geographic shifts in Anatolia and the Caucasus.
Balkanatolia, as a result, has alternatively been depicted either as a discontinuous archipelago or a wide and continuous island, according to scholarship cited in the study, reflecting periods of partial submergence and reemergence from water.
The causes of such tectonic shifts and water levels in “deep time” Eurasia are among things researchers continue to study about Balkanatolia’s impact on the biogeography of the present.
“We have animals on Balkanatolia living side by side that never cohabitate anywhere else on Earth,” Beard told NBC. “How did that happen?
Tethys Ocean and Mantle Convection
The map on the left, which is based on the new study, shows how the landscape changed over 65 million years as Africa approached Europe and Asia. The box on the right shows mantle density at different depths along the red line marked A and B.
The large, extinct elephant species Gomphotherium made its way into Asia.
They have now pieced together knowledge about what happened.
closed.
rhinos, big cats, and many other animal groups migrated into Africa.
away from Africa 90 million years ago.
ago.
Afar is a hotspot with hot rock masses rising from deep within the mantle.
uplift and volcanic activity.
tectonics and the collision.
Atlantic Oceans.
is a professor of geology at the University of Bergen.
climate models, according to Gaina.
writes.
Reference:Straume et al. mantle convection and Tethyan closure in the Eastern Mediterranean', Nature Reviews Earth & Environment, vol.
Paul Salopek's Out of Eden Walk: Tracing Human Migration
Explorer Classroom | Out of Eden Walk: Updates from China with Paul Salopek
Paul Salopek is an award-winning journalist and National Geographic Explorer. He is also a walker. And he is on a very long walk. One that will last at least 10 years. One some of our human ancestors took about 60,000 years ago, by some estimates.
In 2013, Paul Salopek set out to walk the path some of our ancestors walked when they migrated out of Africa. He has named his expedition the Out of Eden Walk. His route will take him from Ethiopia to the Middle East, through Central and Southeast Asia, and across China.
The land bridge our ancestors used to cross from Asia to North America has long since disappeared. So Salopek will take a ship across the Pacific Ocean. He will then walk through the West Coast of the United States and Mexico. He will cross Central America to South America and walk along its western coast to Tierra del Fuego-the southernmost tip of the continent.
Just as some of our ancestors did, Salopek will travel mostly along the outside edges of the continents, near oceans, and seas.
As he walks, Salopek is documenting the places he travels and the people he meets. Salopek is also telling the stories of our human history, from the earliest humans to our more recent past. Some of the places he has walked through have clues that can help us understand early humans and our even-earlier homininancestors.
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