Well, I think jealousy must confer a survival advantage, or it wouldn’t stick around. I can see how it would work in relationships. If a man wasn’t jealous about his partners other admirers, and didn’t try to get rid of them, than someone else would father that woman’s children. Similarly, on the woman’s side, if she weren’t guarding her partner jealously, he might wander off, and not be around to help bring up the kids.
But jealousy about possessions? I guess that might encourage you to acquire something better, or steal what the other person has, and if you are successful, then you are better off. So jealousy would encourage unethical behavior, and that’s why modernday humans try to temper the emotion. We also realize that if we are all stealing from each other, there can be no trust, and no society, and no mutual cooperation.
Yet, as a community, we can be jealous of other communities, and that gives us motivation to fight to get a better share from the communal pot (federal govt, e.g.). So jealousy could help by motivating people to attempt to acquire a bigger share of resources, thus enhancing chances of survival. Non-jealous people who didn’t care and were willing to share would probably not survive, or not reproduce, thus eliminating the non-caring, non-jealous genes from the gene pool.