Book excerpt: Disgust originated to prevent humans from eating poisonous food, but this simple safety mechanism has since evolved into a uniquely human emotion that dictates how people treat others, shapes cultural norms, and even has implications for mental and physical health. This book illuminates the science behind disgust, tackling such colorful topics as cannibalism, humor, and pornography to address larger questions including why sources of disgust vary among people and societies and how disgust influences individual personalities, daily lives, and values. It turns out that disgust underlies more than we realize, from political ideologies to the lure of horror movies.