Hmmm...little pro-evolutionary comments. I guess I'll chuck mine in.
As usual, many of you seem to be missing the entire point of the analogy.
A clock can do one thing and one thing only - keep time. That's it. It has no other purpose. Thus, it is 'simple'. How difficult it is to make has nothing to do with the matter at hand - only that it has 1 function, and it has to be as complicated as it is to do that 1 function well.
Take an ink blot test, for example. It could be seen as a butterfly, star, elephant, bird, tree, etc. It can be essentially anything. Useful for art, examining someone's mind, etc. In its simplicity, it gains many uses.
If you want it to be useful for one thing and one thing only, you must start adding rules. Adding complexity.
What the author is saying, basically, is that the human mind is more like the ink blot test than a clock. It DOES NOT have one and only 1 function - it has many. Literally, it can be used for anything at all. Thus, it's design is 'simple'.
At least, that appears to be his point.
I don't happen to agree, but at least I have an open mind about it.