Beringia was a vast, prehistoric landmass that intermittently connected Asia and North America over millions of years. This expansive, now-submerged region lay primarily beneath the Bering Strait, the Chukchi Sea, and the Bering Sea. It functioned as a biological bridge, facilitating the dispersal of plants, animals, and the first human populations between the Old and New Worlds. Its existence is central to understanding the distribution of life across the Northern Hemisphere.
Geological History of the Land Bridge
The formation and disappearance of Beringia were tied to the cyclical nature of the Pleistocene Epoch, or Ice Ages. During global cooling, massive continental ice sheets accumulated across North America and Eurasia. This locked up immense volumes of water as glacial ice, causing a worldwide drop in sea level.
Global sea levels dropped by 400 feet (120 meters), exposing the shallow seafloor of the Bering Strait. This created the Bering Land Bridge, a landmass extending up to 1,000 miles (1,600 km) from north to south. The most recent phase of emergence began around 35,700 years ago and lasted until approximately 11,000 years ago.
The landmass reached its greatest size around 20,000 years ago, during the Last Glacial Maximum. As temperatures warmed, the ice sheets melted, and water returned to the oceans, causing sea levels to rise. This gradually inundated Beringia until the connection was severed, forming the modern-day Bering Strait.
The Beringian Landscape and Ecosystem
Most of Beringia remained unglaciated due to its cold, arid climate, even while much of the northern world was covered by glacial ice. This environment supported the Beringian Steppe-Tundra, or “mammoth steppe.” The landscape was a cold, dry, and productive grassland ecosystem, unlike any modern environment.
The vegetation consisted primarily of high-productivity grasses, sedges, herbs, and willow shrubs; trees were largely absent. This nutritious forage sustained large herds of grazing animals. Scientists classify the mammoth steppe as a non-analog ecosystem because it has no exact modern counterpart.
This forage supported a community of Pleistocene megafauna. Large herbivores included woolly mammoths, steppe bison, horses, and saiga antelopes. Apex predators like the steppe lion, wolves, and the giant short-faced bear followed these herds, forming a robust food chain. Fossil evidence is abundant across the former landmass.
The Great Migration into the Americas
The Beringian landmass provided a pathway for the first human populations to move from Asia into the Americas. Ancestral Native Americans migrated from Siberia and occupied Beringia for an extended period, known as the Beringian Standstill. Genetic evidence suggests this isolation lasted 10,000 to 15,000 years, beginning roughly 25,000 years ago.
During this standstill, the population diverged genetically from its Asian roots, forming the distinct genetic lineage found in all modern Native Americans. As the climate warmed and the ice sheets retreated, two main routes potentially opened for movement south. The first was the “ice-free corridor,” a gap between the Cordilleran and Laurentide ice sheets, estimated to be viable for travel around 13,000 years ago.
The alternative, which has gained support, is the “coastal migration” route along the Pacific Rim. This hypothesis suggests early peoples used watercraft to follow the coastline south, moving past the ice sheets. Archaeological dating indicates that sections of the Pacific coast became ice-free and productive as early as 17,000 years ago, allowing for an earlier entry. Ancient sites in South America dating back over 14,500 years support the coastal route.
Modern Legacy and Evidence
Today, Beringia’s legacy is preserved in its geographical remnants and scientific evidence. The Diomede Islands, St. Lawrence Island, and the Pribilof Islands are peaks of the former land bridge that remain above the water. A large part of the eastern section is protected as the Bering Land Bridge National Preserve in Alaska.
The most compelling evidence comes from genetic studies of ancient and living populations. Analysis of mitochondrial DNA traces Native American ancestry back to a founding population isolated in Beringia. The discovery of the remains of an infant, dubbed the “Ancient Beringians,” further details the history of human occupation.
These genetic findings, combined with archaeological discoveries like the Upward Sun River site, provide a timeline for human migration and population divergence. Ongoing research refines the timing and pathways of the initial settlement of the Americas, confirming the land bridge as an important gateway.