Why do we have the ability to get angry?

I mean, really, why do we need to do that? How did it evolve inside us? And do other mammals feel anger, or do we just place that label on what is really, in them, fear? Watching babies, you can plainly see that the ability to feel anger is something we are all born with. But why? What does that ability do for us? Is it something we need/needed to survive? And what about all the other "negative" emotions? What do they do for us? How did we come to have them? Why do we need them?

On the other hand, if you are a creationist, why did God form us with the ability to get angry? Why did he give us the ability to fight? To kill? Didn't Jesus teach peace? Acceptance? Turn the other cheek and all that stuff? So... why did God make us with the inborn ability to feel anger, hate, jealousy, greed, etc.?

I'm not sure what I am. And I don't see why the two are mutually exclusive. Why can't God have set us on the path to evolution? Who says that he had to just snap his fingers and make us "full blown"? None of us was there, how do we know by what method he made us? Who are we to say that evolution was not his way of making us? Yes, I know the Bible says that God made the Earth and all things on the Earth in 6 days and on the 7th day he rested. Well, who are we to say that God's days are the same length as our days? Perhaps his days are equal to a million, million of our days, who knows? Perhaps he put the "spark" into the primordial stew and began life on it's way to what we now have. Why can't it have happened that way: Say God gave up the spark and then sat back to watch what became of it. I don't have a problem with that. Then he sent his only begotten son to us when we were supposedly evolved enough to need him. What's wrong with that theory?

It could have happened that way. All things are possible with God, right? Either he is God, or he isn't God. (I use the general term "he" here for ease of writing). Either you believe that anything and everything is possible with God or you don't. How can anyone put limitations on God, or say what God did or didn't/could or couldn't do? I confess that some days I still wrestle with whether or not there is a God. But most days I come to the realization that I do believe, just not in the way organized religion would have me believe.

But back to my point: whether life appearing on this planet was sheer accident and we did evolve from sludge and are supposedly still evolving; or some all knowing, all powerful Being, which most people call God, formed us and breathed life into us. Whichever way it happened, why do we need anger, jealousy, greed, hate, irritation, annoyance? The emotions that most usually get us in trouble. Why do we need gluttony for crying out loud? Whoever thinks that is a good idea? But really, what do they do for us? I'm trying to think of something that the ability to feel anger does for me personally, and I can't. All I can think that it does for me is make me feel bad and usually get me in trouble, if I don't control it. Is that it? Do we need those things so we can struggle against them? Is that what makes us human?