“…A substantial portion of this research has focused on the pathogen threats posed by intergroup interactions (Faulkner, Schaller, Park, and Duncan, 2004;Fincher, Thornhill, Murray, and Schaller, 2008;Letendre, Fincher, and Thornhill, in press;Navarrete and Fessler, 2006;Navarrete, Fessler, and Eng, 2007;Schaller and Murray, 2008;Thornhill et al, 2009). Crushing epidemics (e.g., smallpox brought to the Western Hemisphere by Europeans) underscore the infectious disease consequences of group interactions.…”