THE ANTHROPIC PRINCIPLE states that the observed laws of the universe are fine tuned for the existence of conscious life simply because if it were not that way, we wouldn't be around to observe it. This may sound tautological, but I believe there's a way to validate this principle through a simple thought experiment.
Imagine a universe called "A", where the laws of physics are such that they provide the absolute bare-bones minimum requirements for intelligent life to just barely eke out an existence. In that universe, intelligent life would only exist in 1 solar system, and evolve on a planet in that system just before the the end of the star's habitable lifespan.
Now imagine a universe called "B". In this universe, the laws of physics are super-ultra conducive to the creation of intelligent life. There would be earth-like planets revolving around each and every star, and each planet would be populated with a plethora of intelligent species.
So, how does our universe compare to these two hypothetical extremes? I think we are closer to "A" than "B." Many wonder "Why are the fundamental laws so fine tuned to allow for intelligent life to exist?" I think an equally good question is "Why aren't the fundamental laws MORE fine tuned to allow for intelligent life to thrive?"
The observation that intelligent life in our universe is rare and fragile supports the Anthropic Principle quite nicely, and consequently lends a bit of credence to the various theories that propose a multiverse.