Beringia is an ancient area that existed long ago. It is located to the west of the Lena River in Russia, to the east of the Mackenzie River in Canada, to the north of the Chukchi Sea at 72° north latitude, and to the south of the tip of the Kamchatka Peninsula. This area includes the Chukchi Sea, the Bering Sea, the Bering Strait, the Chukchi and Kamchatka peninsulas in Russia, Alaska in the United States, and Yukon in Canada.

This region covers land on the North American Plate and Siberian land east of the Chersky Range. At certain times in the past, Beringia was a land bridge called the Bering land bridge or the Bering Strait land bridge. This bridge was as wide as 1,000 km (620 mi) and as large as the combined areas of British Columbia and Alberta, covering about 1.6 million km² (620,000 mi²). It allowed plants and animals to move between Asia and North America. Today, only a few islands, such as the Diomede Islands, the Pribilof Islands (St. Paul and St. George), St. Lawrence Island, St. Matthew Island, and King Island, are visible from the central part of the old land bridge.

Scientists believe that a small group of people, no more than a few thousand, moved to Beringia from eastern Siberia during the Last Glacial Maximum. These people later expanded into the Americas after glaciers that blocked the way southward melted. This migration happened before the land bridge was covered by the sea about 11,000 years ago.

Geography

In the late 1800s, scientists found bones of ancient mammals on the Aleutian Islands and in the Bering Sea. These discoveries suggested there might have been a land connection beneath the shallow waters between Alaska and Chukotka. At first, scientists thought the land connection was caused by the movement of Earth’s plates. However, by 1930, changes in ice levels that caused sea levels to rise and fall were believed to be the reason for the Bering land bridge. In 1937, Eric Hultén studied plants near the Aleutians and the Bering Strait. He found tundra plants that had once grown on a land area now under water. He named this area Beringia, after Vitus Bering, who explored the strait in 1728. Plants from the Erythranthe and Pinus families are examples of this, as similar species are found in Asia and the Americas.

American geologist David Hopkins later expanded the definition of Beringia to include parts of Alaska and Northeast Asia. Beringia was eventually described as stretching from the Verkhoyansk Mountains in the west to the Mackenzie River in the east. During the Pleistocene epoch, global cooling caused glaciers to grow and sea levels to drop. These changes created land connections in many places. Today, the Bering Strait is about 40–50 meters deep. The land bridge formed when sea levels were more than 50 meters lower than they are now. A study of sea level changes showed that a seaway existed from about 135,000 to 70,000 years ago, a land bridge from about 70,000 to 60,000 years ago, an intermittent connection from about 60,000 to 30,000 years ago, and a land bridge from about 30,000 to 11,000 years ago. After the last ice age, rising sea levels reopened the strait. Since then, post-glacial rebound has slowly lifted parts of the coast.

During the last glacial period, large ice sheets in North America and Europe trapped enough water to lower sea levels. For thousands of years, the ocean floors of shallow seas, including the Bering Strait, the Chukchi Sea to the north, and the Bering Sea to the south, were exposed.

Refugium

The last glacial period, often called the "Ice Age," lasted from about 125,000 to 14,500 years before present (YBP). It was the most recent cold period during the current ice age, which happened near the end of the Pleistocene epoch. The Ice Age reached its coldest point during the Last Glacial Maximum, when large ice sheets began to spread from about 33,000 YBP and reached their farthest points around 26,500 YBP. Ice began to melt in the Northern Hemisphere around 19,000 YBP and in Antarctica around 14,500 YBP. The land bridge between Asia and North America was finally covered by rising sea levels around 11,000 YBP. Evidence shows that melting ice was the main reason for a sudden rise in sea levels around 14,500 YBP. Fossils found on many continents suggest that large animals died out near the end of the last glacial period.

During the Ice Age, a cold and dry area called the mammoth steppe stretched from the Arctic islands to China and from the Iberian Peninsula across Eurasia to Alaska and the Yukon. This area was blocked by the Wisconsin glaciation. The plants and animals in Beringia, the land bridge region, were more similar to those in Eurasia than to those in North America. Beringia received more moisture and cloud cover from the North Pacific Ocean than the dry areas around it. This moisture created a shrub-tundra habitat that supported many plants and animals. In eastern Beringia 35,000 YBP, the northern Arctic was 1.5°C warmer than today, while the southern sub-Arctic was 2°C cooler. During the Last Glacial Maximum 22,000 YBP, summer temperatures were 3–5°C cooler than today, with some areas in the Yukon being as much as 7.5°C cooler. In the driest and coldest times of the Late Pleistocene, moisture levels varied along a north-south line, with the south receiving more cloud cover and rain from the North Pacific. Beringia, like much of Siberia and parts of China, was not covered by glaciers because there was very little snowfall.

In the Late Pleistocene, Beringia had many different types of plant and animal communities. From about 57,000 YBP to 15,000 YBP, steppe-tundra vegetation covered much of Beringia, with grasses and herbs growing in large areas. There were also patches of shrub tundra and small areas with larch and spruce forests, as well as birch and alder trees. Scientists believe that the large number of big animals in Beringia during this time required a rich and productive environment.

Studies in Chukotka, on the Siberian side of the land bridge, show that from about 57,000 to 15,000 YBP, the environment was wetter and colder than the steppe-tundra to the east and west. Some parts of Beringia warmed after 15,000 YBP, which may have helped animals move across the region. As the climate warmed, more food became available for animals that eat plants and a mix of plants and meat. At the start of the Holocene, some species that needed more moisture left Beringia and spread westward into northern Asia and eastward into northern North America.

The land bridge between Asia and North America first appeared around 70,000 YBP. However, between 24,000 and 13,000 YBP, the Laurentide and Cordilleran ice sheets joined, allowing animals and plants to move between Beringia and North America. The Yukon corridor opened around 13,000 YBP, reconnecting Beringia with North America until rising sea levels closed the land bridge around 10,000 YBP. During the Holocene, many species that needed more moisture spread eastward and westward, while forest-adapted species moved north from the south. Animals that needed dry conditions became rare or disappeared.

The environment in Beringia changed as the climate shifted, affecting which plants and animals could survive. Beringia acted as both a barrier and a bridge: during colder times, glaciers expanded and rainfall decreased. During warmer periods, clouds, rain, and snow changed soil and water patterns. Fossil evidence shows that spruce, birch, and poplar trees once grew farther north than they do today, indicating that the climate was once warmer and wetter. The environment in Beringia was not the same everywhere. Studies of woolly mammoth bones show that western Beringia (Siberia) was colder and drier than eastern Beringia (Alaska and Yukon), which had more varied ecosystems.

Grey wolves experienced a major population drop around 25,000 YBP during the Last Glacial Maximum. After this, a single group of modern wolves expanded from their Beringia refuge to repopulate their former range, replacing older wolf populations in Eurasia and North America. A now-extinct pine species, Pinus matthewsii, was found in Pliocene sediments in the Yukon area.

The presence of animals unique to Siberia and North America in Beringia has led to the "Beringian Gap" hypothesis, which suggests an unconfirmed geographic barrier blocked movement across the land bridge when it emerged. However, many dry steppe-adapted animals, like saiga antelope, woolly mammoths, and caballid horses, could move freely across the land bridge. Some animals, such as woolly rhinos in Siberia and species like Arctodus simus and Camelops in North America, were limited to certain areas. The absence of mastodons and Megalonyx in some regions may be due to their limited presence in Alaska and the Yukon during interglacial periods. Ground sloth DNA has been found in Siberia, suggesting some species may have crossed the land bridge.

Human habitation and migration

The Ancient Beringian (AB) is a group of people identified through the study of an infant’s DNA found at the Upward Sun River site (called USR1), which is about 11,500 years old. This AB group split from the Ancestral Native American (ANA) group around 20,000 years ago. The ANA group formed between 20,000 and 25,000 years ago through a mix of East Asian (about 65%) and Ancient North Eurasian (about 35%) groups. This matches the idea that people first reached the Americas through Beringia during the Last Glacial Maximum.

It is thought that the first people to reach the Americas were Paleolithic hunter-gatherers (called Paleo-Indians) who crossed from the North Asian Mammoth steppe into North America via the Beringia land bridge. This land bridge connected northeastern Siberia and western Alaska because sea levels dropped during the Last Glacial Maximum (26,000 to 19,000 years ago). These early groups moved south of the Laurentide Ice Sheet, either by land or sea, and spread quickly across North and South America by about 14,000 years ago. Some evidence suggests they may have arrived earlier, before 20,000 years ago. People living in the Americas before about 10,000 years ago are called Paleo-Indians. Native peoples of the Americas are connected to Siberian groups through similar blood types and genetic patterns found in DNA.

Around 3,000 years ago, ancestors of the Yupik people settled on both sides of the straits. In 2012, the governments of Russia and the United States announced a plan to create a shared area in Beringia to protect its heritage. This agreement would link the Bering Land Bridge National Preserve and the Cape Krusenstern National Monument in the U.S. with Beringia National Park in Russia.

Previous connections

Biogeographical evidence shows that North America and Asia were once connected. Similar dinosaur fossils have been found in both regions. For example, Saurolophus fossils have been discovered in Mongolia and western North America. Relatives of Troodon, Triceratops, and Tyrannosaurus rex originally lived in Asia.

The oldest known Canis lupus fossil is a tooth found in Old Crow, Yukon, Canada. This tooth is from sediment that is 1 million years old, though scientists are unsure about the exact age of the sediment. A slightly younger Canis lupus fossil was found in Alaska, in sediment dated to 810,000 years old. These discoveries suggest that wolves originated in eastern Beringia during the Middle Pleistocene.

Fossil evidence also shows that primates and plants moved between North America and Asia about 55.8 million years ago. Around 20 million years ago, North America had the last natural exchange of mammal species. Some mammals, such as ancient saber-toothed cats, lived in Europe, Africa, Asia, and North America. Over time, more plants, animals, and fungi generally moved from Asia to North America than the other way around.

• A map shows the connection between North America and Asia during the Late Cretaceous period (~80 million years ago).
• The map includes past (purple) and current (orange) land bridges on a bathymetric equirectangular projection centered on 45° E.