The modern Inuit of Canada and Greenland are descended from whale-hunting Thule migrants, who moved out of the Bering Strait approximately 800 years ago. The Thule Inuit have been known to science since Danish explorer Knud Rasmussen's 5th Thule Expedition in 1922-23, when archaeological remains of early Thule settlements were found in northwest Greenland. The Thule Inuit moved into the Arctic lands of the Dorset, a paleo-eskimo population native to Arctic Canada and Greenland for at least 4000 years; the Dorset vanished with the appearance of the Thule. The Thule migration occurred at the end of the Medieval Warm Period (800-1200 CE), which was followed by the Little Ice Age (1350-1850 CE).

Once thought to have been a gradual centuries-long advance, archaeologists now believe the first Thule migrants crossed the entire Canadian Arctic to the rich sea-mammal hunting waters between Greenland and Ellesmere and Baffin Island in only two or three years. Distinctive and fragile pottery from Bering Strait villages, unlikely to have survived more than two seasons of use, has been found in these areas. The remarkable speed of the Thule advance was made possible by their mastery of dog sleds and walrus skin covered umiaks, large volume whaling boats that could be sailed or rowed on open seas.

Until recently, the conventional scientific belief was that the Thule migrated into the Canadian Arctic because of the warming climate during the Medieval Warm Period (800-1200 CE), following their prey, the bowhead whale. Now, a remarkable new theory with growing support in the archaeological community proposes that the Bering Strait Thule experienced a serious iron shortage related to disruptions in East Asian trade routes after the rise of Ghengis Khan in the 13th century. Knowing of sources of iron in the Canadian Arctic, Thule migrants set off on a journey eastwards in search of this precious commodity. The iron they eventually discovered would have been both meteoric (Cape York meteors) and European, because Norse Greenlanders were trading into the Eastern Canadian Arctic in their quest for walrus ivory and other Arctic luxury goods.

Since the end of the Cold War, a generation of archaeological research on the Alaskan and Russian sides of the Bering Strait has revealed evidence of a highly competitive and relatively densely populated culture region 1000 years ago. The emergence of hierarchical village societies, containing over-classes of artists and political leaders, and supported by slaves, is linked to their learning to hunt for the largest mammal in their environment, the bowhead whale. Intense competition for hunting grounds, over-population, and the ability to maintain permanent militias were factors in the emergence of violent conflict. Archaeologists have uncovered fortified Bering Strait villages, and the Thule were known to wear Chinese-style slat armour and use the Mongol recurved bow.

Little is known about the causes for the disappearance of these two populations in the 14th and 15th centuries, but their withdrawal coincides with the arrival of the Thule Inuit. There is no concrete archaeological evidence of fighting between indigenous Norse and Dorset and incoming Thule, but a body of circumstantial evidence suggests this was a strong probability. Inuit oral history in both Arctic Canada and Greenland contains many stories of conflict with earlier inhabitants, as well as detailed descriptions of the habits and appearance of the Dorset and Norse. Norse sagas from Greenland also describe violent encounters with skraelings, the Norse term for Inuit. Finally, recent discoveries from the Bering Strait have proven the Thule were accustomed to fighting, carried weapons of war, and were able to move in large groups long distances in their large whaleboats.