IMO, the only broad purpose to life, that applies to everything living, is to evolve. Our individual purpose is something we choose ourselves (wether we consciously choose it our not). Although I do try not to think about these things too indepth, because it tends to be quite mind-boggling as you go further down the track, and then I can't sleep for worrying about the sheer miracle of existence. Which usually leads to me wondering if we do exist at all, or if we're just an illusion. Makes my head hurt just thinking about it really.