Final answer:
The Northwest Coast tribes likely believed they descended from mythic or totemic animals, considering the importance of animal-named clans in their society.
Step-by-step explanation:
The Northwest Coast tribes, such as the Tlingit and Haida, had a rich cultural tradition that was closely linked to the natural world. They supported themselves through hunting, gathering, and particularly through fishing, with salmon being a vital source of protein. In terms of cosmology and descent, these tribes believed that they descended from various important animals and entities that were significant to their cultural beliefs and environment. Considering the cultural importance of animals such as the raven, salmon, eagle, and killer whale, which were also the names of clans, it is reasonable to conclude that the Northwest Coast tribes might have believed they descended from a mythic animal or perhaps a totemic animal that represented their clan.