This nice conceptual piece from Justin Renteria augments an article in The Chronicle of Higher Education. In it, the author suggests that having enemies — and even creating new ones where none exist — is part of our human biology. Early humans evolved by fending off hostile animals, as well as hostile bands of fellow humans. We battled "others" to protect our tribesmen and resources, and we battled them to steal and secure their resources. Today, we have a pronounced ability to make enemies. An almost genetic need to have one, even if only to swell our patriotic pride.