“…That is, people will engage in behaviors which can proactively avoid pathogen risk in the long run (e.g., hand washing before meal) under conditions in which no immediate pathogen threat is detected ( Ackerman et al, 2018 , Schaller et al, 2021 , Stevenson et al, 2011 ). As infectious diseases have imposed selection pressure on human ancestors ( Schaller et al, 2015 ), many cultural norms serve to proactively defend people against pathogen threat ( Murray and Schaller, 2012 , Schaller et al, 2015 , Schaller et al, 2021 , Stevenson et al, 2011 ). Given that features of in-group assortative sociality (e.g., xenophobia) are adaptive anti-pathogen strategies developed under localized host-parasite coevolutionary races ( Fincher & Thornhill, 2012 ), strong in-group assortative sociality functions as a social defensive mechanism for reducing transmissible risks of novel infectious diseases in the long run ( Morand & Walther, 2018 ).…”