How do people become professional programmers? Many people go the "traditional" path through a computer science or software engineering education and from there into professional programming work.
K. Imamura, R. Heckendorn, T. Soule, and J. Foster. Genetic Programming, Proceedings of the 5th European
Conference, EuroGP 2002, volume 2278 of LNCS, page 172--181. Kinsale, Ireland, Springer-Verlag, (3-5 April 2002)