Anger: natural instinct in mankind or artificial one?

i want a well thought answerAnger: natural instinct in mankind or artificial one?
I believe that anger is a natural instinct in mankind. Imagine if a member of your family was shot; you're first reaction is anger / revenge, it's so natural there is no conscious thought process involved - but after a while you are able to think and that initial anger and need for physical revenge subsides and is replaced by a methodical need for revenge ie: legal system, protect remaining family members etc.Anger: natural instinct in mankind or artificial one?
I think it's totally natural all of us feel anger jealousy sadness happiness. It's just a very different emotion that could cause mostly bad things and make others loath you. But about the artificial part there are drugs that the psychiatrists give that have anger as a side effect. It really is so much different than the anger usually people know you see something else in a person who is on drugs with such a side effect. Really it's kinda freaking you out...
Of course natural. Anger is actually good for you. Imagine if you didn't get angry? You would have everything bottled up and everyone would be explosive. It helps us be funcitonal human beings. And it's not like it occurs just in humans. Animals get enraged as well. Of course, it's less sophisticated and they rarely enact revenge, but still, it's natural just as laughter is natural to us.