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A Brief Insight into the Land Bridge Theory

A Brief Insight into the Land Bridge Theory

The Bering Strait Land Bridge Theory of migration is one of the most debated theories on the settlement of the Americas. Now that shouldn't really come as a surprise; after all, it's impossible to discuss this topic without raising a storm.
ScienceStruck Staff
Bering Strait Trivia
Though the Bering Strait is named after Danish Captain, Vitus Bering, the first European to sail through it was Russian explorer, Semyon Dezhnev.
Christopher Columbus is widely considered the discoverer of America despite the fact that there is ample evidence to suggest that he was not the first European to reach the Americas. Before him, Norse explorer, Leif Erikson had landed in North America and even established a settlement at Vinland―the northernmost tip of Newfoundland in Canada.

However, even Erikson's pre-Columbian discovery of North America may not be the first instance of humans crossing over into what we know as the New World. There exist theories which suggest that the ancestors of Native Americans crossed over into the New World several thousand years ago, most probably in response to overcrowding and resultant competition for resources.
The Land Bridge Theory
Also known as the Bering Strait theory or Beringia theory, the Land Bridge Theory is one of the most popular model of migration into the New World. It proposes that the first people to populate the Americas migrated from Siberia (Asia) to Alaska (North America) by crossing the land bridge that once existed where the Bering Strait―linking the Arctic Ocean with the Bering Sea―exists today. This migration is believed to have happened fourteen to twenty thousand years ago.
Bering Bridge
A map showing the migration of early humans from Siberia to Alaska via the Bering Bridge.
Supporting Evidence
The Land Bridge Theory was first proposed by Spanish naturalist, José de Acosta in 1590. However, it only gained wide acceptance in the 1930s after biological connections between Siberia and Alaska were established. Somewhere between 1929 and 1937, researchers recovered spear points from a place called Clovis near New Mexico. The study of these spear points revealed that they were similar to artifacts that were recovered from Beringia. This was by far the most important evidence to back the Land Bridge Theory. Researchers were able to establish the timeline of migration of early humans from Asia into North America when carbon dating tests revealed that these spear points were more than 13,500 years old.
Seconded By
Also backing the Land Bridge Theory was marine regression towards the end of the Pleistocene. During this period, global sea levels were 300 ft lower than today, as most of the water on the planet was stored in the form of continental ice sheets in the Northern Hemisphere. (Sea levels only began to rise and reached current levels about 6,000 years ago.) As a result of low sea level, a massive tract of land, eventually named the Bering Bridge, was exposed. It was over 1000 miles wide at some places and connected Siberia to Alaska. Some researchers are of the opinion that the Bering Bridge had tundra vegetation and, thus, they believe that it supported species like the modern-day caribou.
Isthmus
In geography, the term 'isthmus' refers to a narrow section of land with water on either sides, connecting two large masses of land. While the Bering land bridge between Siberia and Alaska is an example of an isthmus formed due to marine regression, the Isthmus of Panama is an apt example of an isthmus formed as a result of continental collision. Hence, these land bridges are also known as isthmian links.
Land Bridge Theory Criticism
When Alfred Wegener's continental drift theory was challenged by the land bridge theory, Wegener came out all guns blazing against the latter. Back then, the continental drift theory was highly criticized. Wegener argued that continents and the deep-sea floor were not made of same rock. While continents were made of granite, the deep-sea floor was made of volcanic basalt. Taking into account the difference in density of these rock types, the land bridge should have bobbed up if it were pushed to the bottom.

Furthermore, the now-separated mountain ranges in Appalachia, Scotland, and Norway are known to be a part of the same range. While early humans and animals could have migrated over the land bridge, the Land Bridge Theory fails to explain the separation of these mountain ranges. But obviously, they cannot migrate. If at all, they must have drifted apart, which is exactly what the continental drift theory suggests.
Interestingly, the Land Bridge Theory is one of the many theories that attempts to explain the settling of early humans into the New World. For instance, there is a theory on similar lines that suggests that Europeans crossed ice sheets covering the North Atlantic to reach North America. And there is yet another, which proposes that Southeast Asians reached North America by boats around 20,000 years ago. What's common to all these theories is that none of them seem to have a concrete explanation for the peopling of the New World.