Not quite accurate; Adrian Thompson (who I assume you're referring to) was using an FPGA. FPGAs allow you to easily reconfigure the design, but it's still being put on a physical piece of hardware.

The design they found with a genetic algorithm wasn't immediately easy to understand because it was using analog effects (ie electromagnetic interference between unconnected circuits) on a chip designed to be digital. However, this probably isn't too surprising in retrospect because they were programming it for the simple analog task of recognizing tones and frequencies. It was a neat outcome, but nothing we don't understand.

This was done back in the mid-nineties mind you.