Heartbreak is every bit as much a psychological adaptation as is the compulsion to have sex with those other than our partners, and it throws a monster of a monkey wrench into the evolutionists’ otherwise practical polyamory. It’s indeed natural for people—especially men—to seek sexual variety. My partner once likened this to having the same old meal over and over again, for years on end; eventually you’re going to get some serious cravings for a different dish. But I reminded him that people aren’t the equivalent of a plate of spaghetti. Unfortunately, we have feelings.

—Jesse Bering

(Previously.)