More often than not, feelings of jealousy flare with such intensity that they burn a hole in the brain, obliterating rational thought and setting off behaviors that create a self-fulfilling prophecy by pushing away the very person one desires, or needs, the most. Think of astronaut-in-training Lisa Nowak, who in 2007, at the age of 44, drove a thousand miles nonstop from Houston, Texas, to Orlando, Florida, with a diaper on, the quicker to kidnap the new girlfriend of a fellow astronaut with whom she had had an affair. Ironic that an impulse that arises from love can so easily destroy it.
Yet jealousy, experts agree, is a survival mechanism, although what is most at stake is a matter of debate. The most destructive of passions—it is a leading cause of homicide—and the least studied, it is, like all emotions, born of necessity, with roots deep in our evolutionary past. Its purpose: to help maintain intimate relationships.
Jealousy is not envy, although the words are often used interchangeably. "Jealousy arises when a relationship is infringed on by a rival who threatens to take away something that is in a sense rightfully yours," explains Richard Smith, professor of psychology at the University of Kentucky. The rival may or may not have features that also incite envy. "But to feel jealous you need not have any sense of what that third party is like," notes Smith. Envy, on the other hand, derives from the basic fact that so much of the spoils of life come from how we compare to others. It arises when another person possesses some trait or object that you want, and includes a mix of discontent, a sense of inferiority, and a frustration that may be tinged with resentment.