Biology ETDs

Publication Date



Social behavior is an important contributor to the success of widely distributed animal taxa, including such distantly related taxa as humans and ants. There is variation in the features and organization of social systems based on ecological constraints and goals, as these alter the costs and benefits of social behaviors, and select for different optimal behaviors for social groups in different environments. I present two bodies of research: an effort to explain geographic variation in the frequency and intensity of human civil conflict; and an effort to describe and model the foraging behavior of colonies of harvester ants of the genus Pogonomyrmex. First, in an investigation of the geographic variation in the frequency of human civil conflict, I show that cross-nationally, intrastate armed conflicts are predicted positively by variation in the intensity of human infectious disease. I present a theoretical model to explain this variation that proposes that risk of exposure to novel infectious diseases imposes costs on intergroup social interaction, and in regions with high intensity of infectious disease these costs create relative poverty and exacerbate conflict over resources. Second, I show that infectious disease predicts other categories of civil conflict, including clan wars, and revolutions and coups. I present a path analysis of the global peace index to test the plausibility of the hypothesized model, including the various indirect effects linking infectious disease to conflict; this analysis supports the importance of the relationship between infectious disease and conflict cross-nationally. Third, I present the results of a study using a computer model of host-parasite coevolution to examine the mechanisms by which localized host-parasite coevolutionary races impose fitness costs on host intergroup interaction, and lead to the evolution of out-group avoidance in mating decisions. In the fourth chapter I present a field study of the foraging behavior of three sympatric species of harvester ants, and their response to variation in heterogeneity in the distribution of foods. Fifth, I present a computer model of ant colony foraging behavior, which I optimized using genetic algorithms for different distributions of food, and whose resulting foraging behavior I compare to the previous observations of harvester ants in the field.

Project Sponsors

University of New Mexico, Department of Biology; Sandia National Laboratories




human warfare, competition, inter-group violence, political values, evolution, behavior, infectious disease, harvester ants, foraging ecology, agent-based modeling

Document Type


Degree Name


Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

Watson, Paul

Second Committee Member

Gangestad, Steve

Third Committee Member

Kodric-Brown, Astrid

Fourth Committee Member

Moses, Melanie