PREFACE

Direct evidence of subsistence resources is provided by faunal remains, macrobotanical materials, plantmicrofossils (i.e., pollen and phytoliths), and food residues, and indirect evidence of subsistence activitiesis provided by the kinds of artifacts and features found at the sites. Organic preservation is often poor atopen sites, however, and the inferences based on artifacts and features are rarely specific to a particularfood resource. A two-pronged approach using modeling to supplement the excavation data is thereforeadvocated. The modeling is viewed as an iterative process involving pattern recognition studies usingexisting data, the development of preliminary models, data collection to test the implications of thosemodels, refinement of the preliminary models and/or formulation of new models, another round of datacollection to test the implications of those models, and so on. Repeated testing and refinement of themodels formalizes the process of integrating new and existing data and of reassessing the conclusionsreached on the basis of those data. It also establishes benchmarks for tracking progress toward addressingthe research problems.The models most commonly developed for cultural resource management applications examine theassociations between site locations and environmental parameters (Kohler 1988). These models aretypically directed toward predicting site locations; that is, to defining areas with higher and lowerprobabilities of containing sites. However, the same pattern-recognition processes can be used to identifycorrelations between site locations and environmental variables reflecting the distribution of potentialfood resources (e.g., vegetation and wildlife habitat for wild plant and animal resources, and soils andmoisture/temperature conditions for cultivated crops). The primary advantage of this approach is that itmakes maximum use of sites with limited data potential. The most useful information will be obtainedfrom sites that can be classified into temporal periods and morpho-functional categories, but even if allwe know about the site is its location, it can still contribute to the overall pattern recognition study.More advanced models utilize optimal foraging theory to predict the food resources most likely to beexploited (Bettinger 1991:83–111; Kelly 1995:73–108; Winterhalder and Smith 1981). Diet breadthmodels may be particularly useful in reconstructing subsistence strategies in New Mexico. In generalterms, diet breadth models are based on a ranking of potential food resources in terms of net return ratesfor the energy and time invested. Return rates are calculated using three factors: 1) the energy (calories)per unit obtainable from the resource; 2) search time – the energy and time expended in locating theresource, which is largely a function of its abundance in the foraging area; and 3) handling time – theenergy and time expended in procuring and/or processing the resource. In formulating the models, it isassumed that a forager is moving randomly through a resource patch, and that he or she will select thecombination of resources that maximizes the net energy intake per unit of foraging time. Given theseassumptions, the general model predicts the optimal mix of resources that will be exploited by the foragerand, equally important, which resources will not be exploited.The use of such models has three advantages. First, the development of diet breadth models does notrequire extensive archaeological data, yet the implications of the model can be tested using archaeologicaldata. Thus the models are particularly useful in contexts like southeastern New Mexico where a relativelysmall number of sites have been excavated and where many sites are likely to yield only limited directevidence of subsistence practices. Second, because search time and handling time are calculatedseparately, the models can be used to examine the circumstances in which use of a particular resource willbe intensified, or in which food resources will be added or subtracted from the diet in response to changesin resource abundance and/or changes in subsistence technology. The underlying assumptions of themodels can also be changed to more realistically mirror the apparent objectives of the prehistoricpopulations. Third, optimal foraging theory provides a battery of explanatory concepts derived fromecology that can be used to explain observed adaptive responses over time, as well as to identify culturalchanges for which ecological explanations are inadequate.4-23