Nobody has nailed down a definitive answer to this question. In my opinion it is because the question is flawed. I started with asking myself what is the point or reason of being here. Quickly I realized the answer becomes much clearer when you ask: What do we absolutely know to not be the reason of existing here?
I don't think the point of being here is to rape the land an other people for a man made construct. IE: money / currency
I don't believe we are here so that we can forcefully impose our will on any other person. I don't have any desire to force anyone to do anything against their will.
Those are are just 2 conclusions I have drawn from asking what are we not supposed to do here...
You are right about those two things, but on a side note, we people still do those things. Also, your question can be rephrased as:
What do we absolutely know to be the reason of existing here?
The very question we humans have asked since day one and as you said no one has a definite answer for it or maybe no one ever will. And maybe that's the beauty of it, a mystery that can't be solved but still, it has to be solved. Some people give an answer to this question from their religion but then there are so many of them who has it right? Or maybe nobody has it right.
Gonna be tough to tell while we are still living. I am pretty sure when you take that last breath and move on it becomes crystal clear. =)
Well, we are in for a surprise then!!