An Abrupt Beginning

It's interesting to note that the CEV lists Mark 1 as a parallel passage to Matthew 3.1-12; Luke 3.1-18; and John 1.19-28.

There's a whole lot going on in Jesus' life before Mark picks up his story, like Christmas and Jesus' visit to the temple when he's twelve.

I wonder why Mark begins his gospel so far into Jesus' life.  This especially intrigues me because I found in my overview last week that I was drawn to Mark's treatment of Jesus' personality in this gospel.  Why is less more as I strive to understand more what Jesus the human was like when he experienced life on earth?