amd, did you get the Darling book yet? I got mine yesterday and just read the chapter on the Rare Earth Theory today.
For the most part, it makes the exact same points we've brought up on this thread. You can't assume the Earth is so ideally suited to life that 1) complex barely arose here by the skin of its teeth, and 2) every last detail about the Earth and its history was essential for complex life to arise.
On the idea of punctuated equilibrium (interesting that no where in that chapter does Darling use that term, but that's clearly what he's talking about in terms of jump-starting or boosting evolution): he points out that the authors of R.E.T. want to have it both ways, sometimes pointing to episodes of instability as being necessary for the path that led to humans and sometimes that instability is anathema to the development of higher life forms.
The fact that life didn't become very complex on Earth for such a long time, might mean that the Earth is less than ideal. In R.E.T., though, you must assume that if anything were even a tiny bit different than the Earth--conditions and events--that complex life would be impossible. As I've said, this is unsupported speculation that could as easily go the other way--that is, that there could be conditions MORE amenable to complex life than the Earth.
As Darling says, the trend that started with the Copernican revolution will most likely continue, and we'll most likely find that there is nothing special or unique about the Earth. Without know anything else, I think it's safest to assume that we are an "average" planet that supports complex life. There's no reason to assume the Earth is the most ideal possible in the galaxy (or beyond!).
I was very surprised to see that my intuition about how all this sounded similar to Creationist talk has a very real source. Guillermo Gonzales, the astronomer that the authors of R.E.T. relied heavily on is, in fact, a Christian apologist. The very same arguments he uses in the context of Rare Earth are the ones he also uses to support the idea of a divine designer. From what I read, the authors were genuinely unaware of these other writings of Gonzales (even though, as he himself says, they weren't covert in the least). Just the language is what made me suspect something like this: fine-tuned, coincidence, accident, miraculous, etc.
All of a sudden I had an image of a giant asteroid (or small moon) carved out wiht a receiver on it, and I heard in my mind, "That's no moon!" I am such a geek!
