The evolutionary advantage of jealousy is that you keep a close eye on your mate and make sure that between you, you only raise your own offspring.

That article is talking about envy, which isn't quite the same.

sgloomi summed them up very succinctly:
Envy is you've got it and I want it.
Jealousy is I've got and you can't have it!

Had I known this at an earlier age, all the agony aunt pages about the stereotypical "jealous boy/girlfriend" would have made much more sense.

*Goes back to VB script*