All GP is done in Lisp?? Sorry but that is far from true! In the EC community C/C++ and Java are the most common languages used. Just take a look at the popular EC libs out there (EO, ECJ, OpenBeagle, TinyGP, etc). Even Python and Matlab are well more accepted as programming languages than any kind of Lisp. It's sad but it's true.
You don't know the "fight" that is to use Lisp in this field/community. The few times I use Lisp is for solo work, because every time I do collaborative work people simply refuse to even considered it. The myths against Lisp are pretty strong and people just refuse to change their minds. Which I think it's kind of ironic since in a science/research environment, people should be more open-minded. Oh well...