I'm not sure if this should be here, or if it's been already, but it's still an interesting article that explains that many animals have complex emotions but only we have the ability to be spiteful:
http://www.newscientist.com/article/dn1 ... otion.html
Maybe spite is the only thing that separates us from the rest of the animal kingdom ? If so, it's not really something to be proud of!
I think that we have 'evolved' emotions as they are now, purely because we evolved large brains and as someone said in an earlier post, too much time on our hands to think up things. But, as we are alive now, this strategy is working, as every other animals' strategy works to keep them alive. Perhaps in the future, as we destroy our resources, greed, spite and all the 'bad' emotions will evolve to some other, or get much worse.