Does the spirit grow?

I have always been fascinated by the idea of a spirit, or a soul.  Does such a thing exist in the form that is commonly accepted?  Some people claim that we are a spirit, put into a body.  As if there are a bunch of premade spirits just waiting to be sent to earth. 

However, this I cannot believe this.  Where is the previous knowledge and experience that would come from any type of previous life?  No, my personal belief is that spirits grow with the person, and are inseparably attached to the mind.  I have no fact, only evidence to back it up with.   For instance, the common idea is that life begins at conception.  I believe this, as one cell in enough to make an organism, and the new DNA means it is a separate organism from it's mother.  So, if those who believe that think that humans have spirits, they assume there is one at conception: a new human. 

What happens in the case of identical twins?  The zygote (a human life) splits apart after conception.  So, does the spirit split too?  No, I don't think so.  Each twin is different from the other, a different path.

If I were to make an exact copy of myself, what would it go on to do?  At that instant, I think we would be two very different individuals.  In fact, I believe that every day, yeah, every moment we become a new person. 

I wonder what would happen if you were able to store all the information in your brain on a computer.  Could you back up your brain at many different parts in your life?  Restore it if you become something you do not want to be?  What happens if you disassemble a person and reassemble it?  Will it be the same person?  Would that be murder?  So many interesting questions.