Guys, I don't think you're going to solve the age-old "nature vs nurture" question any time soon. Why does it have to be exclusively one or the other anyway? My view would be that some behaviours and responses are innate and hard-wired (call it human nature if you want - what exactly constitutes it is definitely debatable) and we can't just magically "erase" them, but we can build societies and environments that minimize the negative sides of that nature and maximize the positive sides. Yes, we can build better environments that will influence people to be "better" but we can't just naively discount the nature side of the equation, we have to take it into account if we want to find workable solutions.
There have been studies on the behavior of new borns and young children and the results were that they are kind, helpful and understanding. They learn the concepts of greed, suspicion, mistrust, xenophobia and aggression, they don't inherit them. It was a multi part BBC feature on human behavior, I believe. Suspicion develops when you made bad experiences. These experiences are caused by abusive behavior of older people, the social environment. It's a vicious learning cycle, but it's not human nature.
That's very interesting. But is it really proof that those behaviours are purely learned? Or is it that certain experiences and environments bring some hard-wired instincts to the surface while others don't? What I mean is - when a child develops suspicion or agression, etc, does it really always "learn" it (by say, watching and mimicking others; how do you define learning anyway?) or is it simply built into our brains to have a tendency to react that way to certain experiences? I suspect it's a bit of both.