Until now archaeologists have been capable of little more than speculation concerning the extent of human mobility in the pre­historic Southwest. According to George J. Gumerman in his Foreword to this book, however, "Shirley Powell's study has changed that. Using a combination of archaeological and ethnological data she has been able to demonstrate that certain periods on Black Mesa in Northeastern Arizona are charac­terized by great mobility while at other times the Mesa had a more sedentary population. She has taken the question of seasonality in occupation from the realm of speculation to that of testable hypothesis." Powell's major concern throughout this study is with behavior variability. Specifically she addresses the adequacy of "behavioral in­terpretations of material culture patterns for the Black Mesa region of northeastern Ari­zona." She notes that sometimes the descrip­tions from which explanations of variability are based are misleading or incorrect. Exam­ining the relationships "among environment, subsistence, and mobility strategies," she emphasizes the role of seasonability in site locational strategies. Using data derived from ethnographic and ethnoarchaeological sources, she develops a model of subsis­tence/settlement interrelationships, which she tests by using "material culture remains from prehistoric sites."