Here is one definition of the anthropic principle :
Only a small range of possible values for the universal constants (such as the mass of an electron) are consistent with the presence of life as we know it. The significance of such apparent fine-tuning of the universal constants is disputed by those who regard it as trivial and those who argue from it to the necessity of life in the universe.
In other words, the universe in general and Earth in particular seem to be designed for the needs of us as a species. If the world was one degree colder or hotter or wetter, we wouldn't be here. I have seen this argument used to prove the existence of a god, and at first I thought it was a joke.
Why? Well, let's take a more down-to-earth, homespun example. Before my parents met, my dad was a teacher, but eventually he decided that he was happier being an auditor. He did the books at the office where my mum worked; that's how they met.
If they hadn't met, they would never have had me. I'm very lucky that he changed his mind and that he was picked to do my mum's employer's audit. No, this can't be a coincidence. There must be a deity, a household god, watching over the Perera family. Otherwise, I wouldn't even exist!
Yes, I wouldn't exist. So what? My dad would have had other little Pereras and my mum would have had little whatevers with some other guy. In a million parallel universes, there are a million parallel scenarios. Not that I believe in Star Trek-like parallel worlds, but you get the point. Just because the-world-as-we-know-it might not exist doesn't mean that the universe grinds to a screeching halt.
In fact, if you look at the definition, it mentions that the physical laws favor the development of "life as we know it". So if the planets had been that much farther from the Sun, we might all be large cold spherical creatures swimming in ammonia oceans on Jupiter, and thinking gratefully that wow, if our planet had been a little bit closer to that faraway star, we might never have evolved. We might even give thanks to a god for this state of events - no doubt this god would also be large, cold, spherical and ammonia-loving, since humans do seem to create gods in their image and likeness. In a million parallel worlds, there are a million different versions of Homo sapiens.
Even if you assume that a god created earth specifically for us, what about creatures like rats and roaches? The world is admirably suited to their needs as well - can this god be as sympathetic to rats and insects as he is to us?
The anthropic principle irritates the hell out of me simply because it relies on a Wide-Eyed Wonder, and anyone who's read enough science fiction - or even watched Doctor Who - knows that there may be more things on heaven and earth than are dreamt of in your Institute for Creation Research. So we might not have evolved - big whoop. Read Dougal Dixon's Man after Man or After Man - a Zoology of the Future to see what would have arisen in our place. Read Brian Aldiss's Hothouse and marvel at the world as it could be - or could have been. Or just watch Star Trek : The Next Generation's delightful episode Parallels. Yes, according to the anthropic principle, you might not be here. But it's fun imagining what would take your place.
Bottom line : our adaptation to the environment doesn't imply a god. Besides, the world was a steaming ball of molten rock 4 billion years ago, and it's going to crumble to hot ashes when the sun goes supernova. Where’s the anthropic principle then?