A Blast from the Past! - Why are we who we are?

I found this in my drafts - from April last year!! It tickled me!

We are who we are becuase of a combination of two things: DNA and upbringing.
We are prodcuts of our parents DNA, where we are born with some traits from either one of them. I believe that the personality traits that we come with are predispositions of our future selves, and our upbringing will enable either all or some of those traits. For example, I assume I was born with the "intelligence" trait, which comes from my parents. I had an upbringing where that trait was able to flourish and become a "real" thing. My parents continued the teachings at home from school with reading, writing and arithmatic.
If, however, my parents neglected my need for further learning out of school, then I may not as be as "intelligent" as I am today. This, therefore, illustrates the point that I who I am today comes from a nurtuing of my predisposed DNA traits. (I put intelligent in quotation marks, as I don't think I'm really as clever as people say I am!)
Why am I suddenly writing what looks like a beginning of a psychology dissertation, which, looking back now, I should have done (I actually did mine on the relationship between personality type A and B and the amount of stress experienced in the workplace. It was interesting, but, as you can see by the title, very complicated!)
Anyway, I digress, I wrote the above as to a train of thought I was having in the shower. It was a 5 minute thought, but a deep one.