We've had this question before so i'll simply copy what I wrote in the "Life's Purpose" thread:

Life has no pre-determined purpose, it's simply what you make of it. I think us humans try to attach too much significance to ourselves, but we must accept that we're just another animal despite having a superior intellect to any other.
It's just like the whole concept of morals. Murder, rape and genocide are considered "evil", but that's because of the overall human consensus regarding things as serious as that, in that it's immoral and evil. If you look at it from a completely indifferent (and suffice to say, correct) perspective you realise that they're not evil at all and it's just what us as humans think it is. That's not to say i'm a Nihilist since I do confine with the standards of society, it's just when you consider the way things actually are then you realise that a lot of things aren't as set in stone as you think they are.