Large mammal resource depression and agricultural intensification: an empirical test in the Mimbres Valley, New Mexico

Abstract

Many archaeologists have argued that reductions in the energetic returns provided by wild resources led people in the past to devote more time to farming. Despite the popularity of this explanation, however, no one has tested the proposition that wild resource foraging efficiency declined in any archaeological case in which there is evidence that agriculture became more important. This dissertation is a study of hunting and farming in the Mimbres Valley of southwestern New Mexico that is directed at conducting such a test.I first present a theoretical model of central place foraging that allows derivation of predictions about the patterns that should be observed in archaeofaunal assemblages in cases in which people experienced depression of large-bodied vertebrate resources. I also discuss an opportunity cost model of time allocation that can be used to understand the conditions under which people might devote increasing amounts of time to farming.I then analyze tightly-dated faunal samples from four Mimbres Valley archaeological sites to evaluate whether hunters in this area experienced resource depression. I focus on large mammals such as deer and pronghorn, which undoubtedly provided the highest post-encounter caloric return rates of any prey in the region. I find that there is evidence of large mammal resource depression and a resulting decline in hunting efficiency between perhaps A.D. 400 and A.D. 800 or 850, while large mammal capture rates apparently remained relatively stable after this time. To the extent that it is possible to control for taphonomic variability, changes in resource procurement strategies and climate change, these factors cannot account for the patterns observed in Mimbres Valley faunal assemblages.Changes in settlement pattern and in both the size and the morphology of the tools used to grind crops suggest that people in the Mimbres Valley allocated increasing amounts of time to agricultural tasks, which likely also reduced the efficiency of agriculture, during the same period in which there is evidence of large mammal resource depression. Existing data from the Mimbres Valley are thus consistent with the hypothesis that reduced wild resource foraging efficiency led to an increase in the importance of agriculture.