In today’s culture wars, religion plays a major role. And in the United States, it often seems to fall on the conservative side of the spectrum. For example, you hardly ever see rowdy hordes of secularists protesting against immigrants or gays, do you? Decades of research has confirmed that religion is correlated with mistrust of outsiders, sexual minorities, and other common targets of prejudice. But why? A new research paper has a fascinating, if unsettling, answer: conservative religiosity is partly an expression of our bodies’ need to protect against disease and germs – and throughout history, nothing has been a bigger source of new diseases than outsiders.