Models represent observed or hypothesized relationships of structure and function in simplified or abstract form. They transform a reference situation, usually a complex system or process, in order to make it more accessible or tractable. Maps scale down a landscape in order to guide the newly arrived over unfamiliar terrain. The logistic equation isolates key demographic variables in order to guide the analysis of exponential population growth in a finite environment. Everything important about a model is shaped by its being an instrument of prediction or investigation. Because of this, the properties of models and the capacities expected of them are nearly as varied as are the goals in using them.
Models are ubiquitous in archaeology, biology, and related historical-evolutionary sciences. They are particularly useful in these fields because the subject matter is complex (which puts a premium on orderly techniques for simplification), multidisciplinary (which puts a premium on devices facilitating clear communication), and in the very early stages of scientific development (which puts a premium on instruments that balance the development of abstract ideas and empirical investigations of their explanatory potency). Models in these fields are non-denominational, in that their use is not restricted to particular theoretical approaches. To the degree we are clear in thinking and communicating about the practice of modeling itself, models bring order and rigor to analytic efforts. This claim recognizes that modeling is an activity (the common use of the gerund gives it away), not a concept, a problem, or a field of knowledge. Skill in modeling de-