what's the point of jealousy?

Negative emotions exist for reason, like pain. When someone has the rare condition of not feeling pain they usually injure themselves all the time. Pain is the body's fairly dim but effective way of shouting at us: "Hey, fix this can't you?" Negative emotions have always seemed highly pointless to me, but then, they too have a necessary role. If you feel one- envy, jealousy, rage, then this is an emotional message that something is out of kilter. This was well known in the past but such knowledge easily transforms, through mass teaching, into merely a 'ban' on such thoughts. People pretend to themselves they don't have them. Or flagellate themselves for being evil. In fact, of course, we all have negative emotions. The Buddhist response- to simply observe the emotion and let it pass is only half the story. The other half is to realise what the appearance of that emotion means to your overall balance. Feeling envious? Let it pass and then examine whether your daily activity is aligned with your more general or higher goals. It is said that a weak man desires to hear only the failings of a strong man. Wishing others ill is another sign suggesting an internal reorganisation is required. Negative emotions are unpleasant for a good reason- there are there to help us shift our everyday operating procedure, nothing more.