This is the only reason why we exist. Around 3 billion years ago, in the primeval ocean, the first self-replicating molecules occured from an accidental arrangement of non-living chemicals. The most adaptable molecules, which were weeeded out through natural selection, began creating 'survivor machines' for themselves as a means of continuing their existence, these first survival machines were the first primitive cells. All animals (this includes homo sapiens) and all biological organisms in general are 'survival machines' created by their genes as a means of propagating their own existence (the existence of the gene, that is, not the organism). Our brains may have evolved to the point where they 'serve' themselves as opposed to our genes but really, this is the only reason why we exist.