The conversation went on and I suggested that the only way to decide once and for all would be if someone was born in isolation and then their creative work could be considered free of outside influence, but would it be original or be a lot like existing works? Of course, practically and morally this isn't really possible as Hans Fritzl demonstrated recently.. :)
The conversation provoked consternation amongst some of us, but I think it's something I've known and been trying to come to terms with on a personal level since I realised this when about 11.
Interestingly, the fourth and last 'section' on this page about feral children suggests that 'being human' is learned. I guess this still leaves room for truly original though, but it will be based on experience and therefore derivative.
Maybe this is all just another symptom of modern life - being spent in the rat race, performing quite abstract tasks in order to earn money to assure a certain standard of life.
On a side note, something that may cause be an fundamental change in human understanding is if scientists are able to go on from creating RNA (a recent breakthrough) to actually creating artificial life. The implications are tremendous.
The other thing I have been amusing myself with recently is looking at Google Earth and finding weird bits of the world; tiny islands that show signs of human habitation, areas of continents and islands that are just interesting to view like Ayers Rock.