<p>The migration of Dene groups from the western subarctic of North America to the American Southwest is one of the longest prehistoric migrations. The starkly different environment of the Southwest, and the presence of groups who had been living in the region for millennia, have made this migration a focus of anthropological and archaeological interest for many years. In the study reported here, we analyzed 547 binary cultural traits pertaining to northern Dene groups, southern Dene groups, and non-Dene groups from the Southwest. First, we focused on the scale of the impact of the migration on the cultural repertoires of the southern Dene. Then, we investigated the relative importance of three processes of change: loss, invention, and borrowing from neighboring non-Dene groups in the Southwest. The results of the first analysis indicate that the migration led to the transformation of the cultural repertoires of the southern Dene. Not only were nearly two-thirds of traits changed, but also a majority of the traits in six of the seven trait categories we employed were altered by the migration. The second analysis indicated that the transformation was not the result of a single process of change. Loss, invention, and borrowing were all involved, and their relative importance varied among categories. These results are consistent with previous characterizations of the southern Dene as flexible and open to change. They also have broader implications. Most importantly, they challenge us to rethink how we approach cases in which there are cultural similarities between ethnographic groups or archaeological sites.</p>