The green-eyed-monster actually serves a useful purpose. In small doses, that is.
Biological anthropologist Helen Fisher recently wrote an interesting piece for Oprah.com about how jealousy is a deeply ingrained and even positive instinct infecting animals and humans alike. While excessive jealousy could certainly drive perfectly faithful partners away, she notes that picking up on a wandering eye has been a good reliable mate filter system. Read: To Ogle or Not To Ogle
Throughout our primordial past [jealousy] discouraged desertion by a mate, bolstering the family unit and enabling the survival of the young. At the same time, it has pushed us to abandon philanderers—and many a futile match—in favor of more stable and rewarding partnerships.
You could certainly make the argument humans are most jealous due to our obsession with monogamy, but even animals get ticked off when they notice the object of their carnal affections choosing another. Read: Dumped? 10 Healthy Ways To Heal
Fisher talks about Passion, an ass flashing chimp that slaps her love interest when passed by for another. Bluebirds, not too unlike the jilted Ryan Jenkins suspected of murdering his philandering wife before committing suicide, get violent if they suspect cheating.
In one experiment involving a breeding pair, evolutionary biologist David Barash waited until the cock was away, and then placed a stuffed male on a branch about three feet from the nest, where the female rested. When the cock returned, he began to squawk, hover, and snap his bill in fury at the dummy. Then he attacked his mate, pulling feathers from her wing. She fled.
We at YourTango do not condone rifling through a lover's things in frantic pursuit of some lunatic cheating hunch. We don't. However, if you find yourself victim to the green-eyed monster, just remind your partner of the famous St. Augustine quote: He that is not jealous is not in love.