State-level pathogen prevalence is associated with fewer interracial marriages and more racially restrictive dating preferences

The behavioral immune system framework has linked higher levels of environmental pathogens with increased racial prejudice and xenophobia, suggesting that avoidance of racial outgroups may be an evolved strategy to avoid infection by pathogens and parasites. Although previous research has found a correlation between pathogen prevalence and racial bias on both regional and individual levels, few studies have examined whether this pattern predicts real-world outcomes. This paper presents two studies linking ecological pathogen prevalence to US state-level variation in interracial marriage (Study 1) and stated racial preferences on an online dating site (Study 2). States with higher pathogen levels tended to have lower-than-expected rates of interracial marriage, and online daters from these states were more likely to indicate more restrictive racial preferences. These results provide support for the pathogen prevalence hypothesis of prejudice and out-group bias by linking environmental pathogen levels to race-based preferences in marriage and dating.