Back story is important to a point. It can set the tone and mood for a character as well as help build those initial layers. In short, back story is one of many building blocks in the writing process.
It is, however, not a replacement for actual development, especially when there's additional people involved. If you end up writing a novel's worth of history for your character, then you might as well be flying solo; you've decided all of the growth on your own, railroading the journey long before it even begins.
Once a level of imbalance like that is reached, back story no longer serves as an aid; it just becomes a hindrance, one that needs to be addressed immediately if you're ever to succeed.
It is, however, not a replacement for actual development, especially when there's additional people involved. If you end up writing a novel's worth of history for your character, then you might as well be flying solo; you've decided all of the growth on your own, railroading the journey long before it even begins.
Once a level of imbalance like that is reached, back story no longer serves as an aid; it just becomes a hindrance, one that needs to be addressed immediately if you're ever to succeed.
