What important changes does the main character undergo?

Jimmy earned a degree in Problematics from Martha Graham and works as an ad writer for pharmaceutical companies. His best friend Crake hired him to work in this capacity at his own firm.

Gradesaver has a complete short-summary already prepared. The page linked below will take you through the story's main points and the changes Jimmy has gone through.

http://www.gradesaver.com/oryx-and-crake/study-guide/short-summary/

I looked at it but it is not what I am looking for. I would like to know what are the major changes Jimmy/Snowman had. Did something change in his personality?

Did you look Jean?

http://www.gradesaver.com/oryx-and-crake/study-guide/character-list/

http://www.gradesaver.com/oryx-and-crake/study-guide/short-summary/