Parasitic organisms make up a significant portion of the biological world. Their hosts are in a constant struggle to combat their fitness diminishing effects – one of those effects being death. Humans have been coevolving with pathogens (like the vast majority of species) since our inception. This has resulted in physiological, behavioral, and psychological defense mechanisms. The aims of this study are threefold. First, the literature exploring this coevolution and the concomitant defense mechanisms is reviewed. Second, that aggression – particularly reactive verbal aggression – is one of these behavioral defense mechanisms is hypothesized and tested via a survey experiment. After analyzing the data, the results from this experiment suggest no correlation between aggression and pathogen defense. Third, we discuss where this coevolution is headed. In the short-term, studies such as this are relevant for developing proximate solutions to pandemic management strategies. In the long-term, further explorations of human-disease coevolution should look at broad patterns in evolution and make innovative predictions as to the trajectory of the human evolution. For example, here it is argued that this research points in two parallel directions: 1) humans are outsourcing (perhaps augmenting) our physiological immune systems to culture, thus constructing a cultural immune system (CIS) via gene-culture coevolution and 2) this is evidence that humans, which are defined not solely as a population of discrete organisms, but also as one “meta” organism, are undergoing a major evolutionary transition.

Keywords: Cultural immune system, behavioral immune system, material immune system, pathogens, disease, aggression, human evolution