Ooooohhhh.... you're making me think too much!!
But seriously... in a nutshell, yes, I think our experiences guide our existence, for the most part. Who hasn't had an experience that changed they way they thought or acted?? While we can go from what we read of, and what we hear, I think it is what we SEE and what HAPPENS to us that are the most influential in our lives. Its one thing to read about cancer or talk to someone who has it, and another thing to have it YOURSELF, for instance.
Human nature exists, but it is very broad. Like I say... people & groups are SO different, its hard to sum them all up, but we do have many common qualities that we share. For example, (most) people want to be happy, people want to be healthy, people want to be around other people, people want to be wealthy, and so on... Its human nature to want these things because experience
, instinct, culture, family have TOLD us these are good things and we should want them.
Its far from uniform: Happiness in the United States would be different than happiness in Madagascar- meaning we require different things to achieve it, but have the same "state of mind" as our goal.
How to explain human nature- It is a basic set of natural, healthy, common, wants, needs, actions, and beliefs based upon the norms and standards of a society. You could also add that human nature has been shaped by experience, but I think that's a given.
Good luck with your paper!! Ethics is fascinating stuff.