An interesting article from Discover magazine discusses the conundrum physicists face in explaining the conditions in the universe for life.

Explaining life on earth away is easy. The earth is one planet in an infinite universe full of planets. One of them being the proper distance from a properly temperatured star to support life as it currently exists is just a matter of odds, and obviously that combination has been hit at least once.

Expanding this explanation to the universal level is a bit harder. in order for the conditions for life to exist (or anything larger than protons for that matter) the universe had to be created with just the right settings. if the gravitational constant was a bit bigger everything would have collapsed into a black hole; a bit smaller planets never would have formed. Changing the speed of light, or the value of the Strong force, or any other number of variables would have created a universe that could not create atoms.

There are three ways we could have arrived at the condition set in our universe to allow it to support life.

Way 1: The universe knew we were coming because it was created by someone or something for us.
Way 2: We got lucky enough to have rolled the dice just right on our only try.
Way 3: Multiverse theory; that just as life on our planet exists because there are an infinite number of planets in the universe and odds favor it happening at least once, our universe can really only explained by the existence of an infinite number of universes. in an infinite number of universes, each having their own laws of nature, at least one was bound to pop up that supports atom's and by extension life. The problem with this theory is that there is absolutely no way to prove or disprove it.