Athabaskan language groups indicate a relatedness of Arctic and Western Canadian, and Southwest groups, such as Navajo and Apache.
Might also ancient (5-10k yrs ago?) Indian mounds in Minnesota indicate an earlier migrating arctic people; the latter suggested by building style of grave sites? Also the number of generations (related to mound size) would seem too great for just a later Hopewell culture (more southern and eastern) indian mound building style influence.
So before the Sioux and Ojibwa migrations, might an Athabaskan language group (or another arctic group) already have arrived at a seemingly more accessible, suitable, and familiar Midwest environment?