Evolution as a Blind Watchmaker

I stumbled across this video through a link on Stack Overflow. As well as providing a compelling argument for evolution against the old foe, intelligent design, it is also a great demonstration of the power of evolutionary algorithms. In the 9 minute video, he describes how evolution would approach the problem of reconstructing a smashed watch, and simulates it in Matlab. The result is an impressive progression from a collection of non-functioning components to a three or four handed timepiece. I am interested to know more about his implementation details, in particular the fitness function he uses. All his code is available, but as a non-Matlab programmer I haven’t invested the time to understand it yet.