The prehistory of Canada can be viewed as a long period of human cultural adaptation to moderating post-Pleistocene environmental conditions. By the time conditions stabilized around 4000 to 2000 BCE, the land's resourceful inhabitants had developed intricate relationships with their environments, based on an intimate knowledge of the biotic setting and reinforced by spiritual bonds.
There is undisputed evidence that the first human beings crossed on a land bridge from Siberia to the unglaciated parts of Alaska sometime before 12,000 BCE. As the continental glaciers melted back, an ice-free corridor developed, about 10,000 BCE, along the eastern flanks of the Rocky Mountains (Environmental Change After 9000 BCE). When the land bridge became inundated as a result of rising water levels, this corridor was used by people to migrate south into the Americas.
The earliest clearly defined group of people in the Americas is known as the Fluted Point culture. These were spear hunters who travelled in small groups, taking such game as mammoth, mastodon, camel, horse, bison, and caribou. The first four of these species became extinct about 8700 BCE, perhaps because of overhunting but more likely as a result of environmental change. As the ice sheets continued to melt back, these hunting groups became culturally more diverse and gradually spread into what are now the southern margins of Canada, where they hunted species such as bison and caribou. By 8000 BCE, the further retreat of the glaciers, ameliorating climate, and the greater diversity of biota permitted more cultural diversification and led to the rise of the Archaic period. On the East Coast a seafaring culture developed, specializing in fishing and hunting sea mammals. Throughout the woodlands the big-game hunters transformed themselves into mixed fishing and hunting groups, while on the plains and tundra big-game hunting persisted, focused on bison and caribou. West Coast groups settled along streams and coastal valleys to take advantage of the abundance of fish and marine mammals.
By about 4000 BCE the biotic environments had achieved considerable stability. The Archaic cultures moved in small clusters of interrelated families, following a seasonal cycle based on the exploitation of aquatic and forest resources. Use of the bow and arrow had spread to all groups. About 2000 BCE, with the rapid expansion of the Palaeo-Eskimo people from Siberia and Alaska, the Arctic was becoming inhabited for the first time; people reached Labrador no more than 200 years later. Between 1000 and 1400 CE these people were replaced by another wave of migrants out of Siberia, the Thule culture, who were ancestors of the modern Inuit (Native Cultural Sequences, 8000 BCE to Europe). By 1000 BCE environmental conditions had become similar to those later encountered by Europeans, and the basic cultural patterns of the historic period were in place across most of the territory that is Canada.
The last major stimulus to the eastern Native cultures before European contact was the northward diffusion of maize about 500 CE, followed by tobacco four centuries later and then squash, bean, and sunflower about 1100 CE (Native Cultural Sequences, 8000 BCE to Europe). Societies that developed horticulture grew rapidly, and their social and political institutions became increasingly complex. By the end of the 15th century, the Huron, Neutral, Iroquois, and others lived in villages of up to 3 000 people and were linked politically in sophisticated inter-tribal confederacies.