I think the whole nature vs. nurture debate is never going to get this resolved. However, one of the most telling longitudinal studies I had ever run across involved studying sons of aggressive (possibly psychopathic) fathers. Longitudinal studies aren't typical done or as successful to pull off as cross-sectional because of the difficulty in keeping up with the subjects over the years....or enough of them. However, in this one study (sorry, I don't know the citing any longer), it wasn't a simple direct correlation, that, highly aggressive dad produced highly aggressive future adult. It came down to, in short, that if the son was able to identify with his father, he had less of a chance to then become an aggressive adult himself. So as you could imagine, fathers largely absent physically and/or emotionally from these sons in turn produced men more like them than not. I would wager that this model probably gets reproduced somewhat with the other more severe characterological disorders (narcissism and borderline, especially). I had a colleague once say something brilliant to me. He said it doesn't have to be a nature vs. nurture argument....behaviors occur in nature.

Some of these characteristics run through my family and I believe there is a genetic component, but choice always enters in as well