Jealousy has been described as a mix of negative emotions including anger, betrayal, and sadness. Historically, psychologists have taken a very general approach to studying jealousy and have only recently begun to scratch the surface of this powerful and, at times, dangerous emotion. Are you a jealous person? How jealous do you get? These questions, while interesting, do not address the specific function and unique design of this psychological adaptation. This book focuses on previously unexplored dimensions of jealousy by viewing it through the lens of social-evolutionary psychology. What are the biological and social origins of this emotion? What are the psychological and environmental cues that trigger jealousy and how do they differ for men and women? This hybrid approach addresses these important questions, and others, with the goal of understanding the often ugly side of jealousy in our modern world and appreciating the forces faced by our ancestors that gave rise to the psychological adaptations we carry with us today.