How should archaeologists and other social scientists tackle the big and little questions about change in socionatural systems? Although fieldwork is certainly the place to start, it alone is not enough to answer troublesome how or why questions. To make sense of what they find in the field, archaeologists build models-possible explanations for the data.Timothy A. Kohler is a professor of anthropology at Washington State University, Pullman. His exposure to the archaeology of New Mexico's Northern Rio Grande region began during a sabbatical year at the School of American Research in Santa Fe. He completes a four-year term as editor ofAmerican Antiquityin 2004.