Gil has an interesting post over at Uncommon Descent about evolving a simple "Hello World" c program. The idea, as he presents it, is to try evolving the simplest functional c program by randomly assembling the non-whitespace letters required. Of course this is impossible, you don't have to try it to know the universe will experience heat death before such a random search succeeds.

PvM's criticism at the Pandas Thumb, which cites a genetic algorithm (GA) that evolves software, misses Gil's point. I don't know the details of the GA involved, but I am sure that it either starts with a functioning piece of software or assigns positive fitness values to non-functional source code. Gil's point, though, was that the simplest functional (i.e. "selectable") c program is already highly specified. In other words, Gil was posing an origin-of-life analogy to evolution. Responding with a paper that shows what can evolve if you design the cost function with a pre-specified target in mind and start with replicating, functional pieces is an exercise in irrelevance.

All the same, I didn't find Gil's analogy very interesting. The primary biological question is not "did the first reproducing organism arise through inconceivable good luck?", but "do simpler intermediates exist which improve the odds?" This is the source of the disconnect between Gil and PvM. I also don't find origin-of-life arguments all that interesting because, well, they don't seem sporting. Demanding that evolutionists explain how life could have arisen in enough detail to prove that its emergence is reasonably probable is too easy; it doesn't give Darwinists a sporting chance.

I do, however, like the idea of comparing biological evolution with some sort of genetic algorithm for program evolution. Cells can be thought of as computers in a lot of ways. In fact, a few months ago there was a Nature article about the similarities and differences between computers and cells. The gist was that the computing modules aren't as distinct in the cell, but they are definitely there.

There would be a lot of details to work out, but I think it could be an interesting idea (I am, of course, almost certainly ignoring reams of prior work :-). Ultimately, though, the biological relevance of these models is going to be the controversial point. What criteria must be met for theoretical results to count as evidence for or against evolution?