A drowned subcontinent
The Bering Land Bridge, known scientifically as Beringia, was a vast subcontinent, was not a narrow isthmus. At its greatest extent around 21,000 years ago, it stretched more than 1,000 kilometers from north to south and covered an area of about 1.6 million square kilometers. This massive expanse of land connected what is now Siberia in Russia with Alaska in the United States. Its existence was a direct consequence of the Last Glacial Maximum (c. 26,500 to 19,000 years ago), when immense ice sheets locked up vast quantities of Earth's water. This process lowered global sea levels by as much as 130 meters (425 feet), exposing the shallow floor of the Bering and Chukchi seas.
Recent geological studies based on Arctic Ocean sediment cores have dramatically revised the timeline for this land bridge. Previous estimates suggested it emerged 70,000 years ago, but new data indicates the Bering Strait remained flooded until about 35,700 years ago. This means the land bridge existed for a much shorter window, from roughly 36,000 to 11,000 years ago, when melting glaciers caused the sea to rise again. The final inundation happened relatively quickly, with the first flooding of the bridge beginning around 10,000 years ago. Today, the average water depth in the Bering Strait is between 40 and 50 meters. The only visible remnants of this immense landscape are islands like the Diomedes and St. Lawrence Island.
The Mammoth Steppe ecosystem
Beringia was not a barren wasteland. It was a complex ecosystem known as the "mammoth steppe." The climate was cold and dry, which prevented the growth of dense forests. Instead, the landscape was a productive grassland dominated by grasses, herbs, and patches of shrub tundra. This environment supported a diverse community of large mammals, many of which are now extinct.
The fauna was a mix of species from both Asia and North America. Woolly mammoths (Mammuthus primigenius) were famous inhabitants, constituting over a third of the total mammal biomass. They roamed alongside steppe bison (Bison priscus), horses, caribou, and muskoxen. Predators included the giant short-faced bear, scimitar cat, and lions. Fossil evidence shows that North American species like camels and horses moved into Asia, while Asian species like the woolly mammoth migrated into North America. This vast, grassy plain provided the necessary food for large grazing herds to thrive. As the climate warmed and became wetter around 18,000 years ago, shrub tundra began to expand, drastically changing the habitat and contributing to the decline of the megafauna.
Genetic and archaeological evidence suggests humans also inhabited this lost land. The "Beringian Standstill Hypothesis" proposes that a small population of human ancestors lived in Beringia for thousands of years, perhaps for as long as 10,000 years, before migrating further into the Americas around 15,000 years ago. Most direct archaeological evidence of this occupation is now inaccessible, submerged beneath the Bering Sea.