Can anything derived from ones own creative mind ever be truly Original?

I'm pondering this thought, following from my recent surfing of the web site TV Tropes. A couple of posts ago I mentioned my discovery of this site, and I guess one way of describing what tropes are, are not to say they are cliches or stereotypes, but familiar conventions found across various forms of media. Whether it is the archetypal stairs found in living rooms of American sitcoms (see my previous post!), or the convention of certain heroine or evil personality traits you'd find in movies ( a really basic example I know ) they are traits that pop up regularly over time and tend to endure, becoming re-born and remastered to enter into the current popular culture more easily. It appears in a variety of media outlets in various contexts, therefore becoming a media trait, a "trope."
There that's my uni essay explanantion.
I was checking out a few different sections, reading about tropes and trying to think of any I may have noticed in movies and TV.
And I'm starting to really think that in this day and age, with the multitude of current film and literature, coupled with the amount already present in our history, for the aspiring writer or film-maker, game creator and tv producer, there can really be no original idea or thought. Every idea is derived from somewhere, every convention already exists, and although your idea may have a different name to it, and your characters may be called Sue and Trent as opposed to Mary and Ken, the story will most likely fundamentally be the same.
Even if we believe to have a truly original idea, our thought patterns, and novel creative inspirations are most likely to have derived from something in our distant memeory, from something we've read, or seen, or even experienced. No matter what convention one may use in his/her literary work, undoubtedly it will already be present elsewhere, somewhere in a form of media text, in this great big wonderful world of ours. So much of our past forms our current and future experiences, so it would be impossible NOT to draw upon knowledge we've learnt or acquired in our past.
Something to think about next time you get an idea..... (!)