Shaul's arguments use linguistic analyses coupled with historic and prehistoric records of migration and cultural interaction. Following the establishment of Piro as a Tanoan language, much of the linguistic analysis involves determining the aspects of Piro that were inherited from the earlier Proto-Tanoan versus those that were incorporated later as a result of borrowing from other languages through cultural interaction. This book lays out the linguistic argument that the similarities between Piro and Tiwan languages result from borrowing, not common ancestry, and it provides a record of contact between groups and linguistic evolution based on these movements.