During the last Ice Age, so much of the world’s water was locked up in ice that the sea fell about 120 to 130 m. Between Siberia and Alaska, where the Bering Strait now separates two continents, a vast stretch of seabed rose into the air. Beringia, as it is called, was not a narrow bridge but a land up to 1 000 km wide from north to south, covering about 1.6 million square kilometres. Mammoths and bison crossed it, and so, in time, did the first people to reach the Americas.
A land, not a bridge
Most of Beringia, on both the Asian and the American side, was covered in mammoth steppe: a cold, dry grassland of grasses, sedges, sagebrush and willow shrubs under mostly clear skies. Summers were 3 to 5 °C cooler than today. Woolly mammoths, steppe bison, horses, caribou, muskoxen and saiga grazed there, hunted by cave lions, wolves and brown bears, and on the American side by short-faced bears.
The bridge in the middle was different. Fossil plants and pollen suggest it was covered in shrub tundra with some trees, and in 2024 researchers presented seafloor surveys and cores from the strait that showed many small lakes, river channels and moss, a wet landscape they compared to the deltas of western Alaska today. It may have been more of a land swamp than a dry bridge.
When it opened
The land bridge appears whenever the sea falls more than about 50 m below its present level, because the strait today is only 30 to 50 m deep. For a long time it was thought to have opened about 30 000 years ago, or earlier. A study published at the end of 2022 used chemical signals in three seafloor cores from the Arctic to show that the Bering Strait was still flooded until about 35 700 years ago, so the bridge emerged surprisingly late, less than 10 000 years before the peak of the Ice Age. It was drowned again about 13 000 to 11 000 years ago as the ice melted.
The first Americans
The ancestors of the first Americans came from Asia across Beringia. Genetic studies suggest that one population lived isolated somewhere in Beringia from about 25 000 years ago for 5 000 years or more, before most of its descendants moved south of the ice sheets by about 15 000 years ago. An infant buried 11 500 years ago at Upward Sun River in Alaska belongs to a lineage known as the Ancient Beringians.
People reached the south earlier than once believed. Fossil footprints in the ancient lake beds of White Sands, New Mexico, have been dated by several methods to about 21 000 to 23 000 years ago, and a 2025 study dated mud from the same lake deposits to 20 700 to 22 400 years. Critics have questioned the dating, and no tools have been found with the tracks. In 2026 archaeologists described a camp near Fairbanks in Alaska about 13 800 years old whose diamond-shaped stone points match sites on the Siberian side.
What remains
Today the Bering Strait is 82 km wide at its narrowest. The two Diomede Islands lie only 3.8 km apart in the middle of it. St. Lawrence Island and King Island are fragments of the old land, and part of Beringia’s Alaskan side is protected as the Bering Land Bridge National Preserve. On St. Paul Island, out in the Bering Sea, an isolated population of mammoths survived until about 5 600 years ago, when the island’s fresh water ran out.
