More of an observation than absolute answer, because that would mean having to define "true purpose" which of course not everyone would be in agreement on. But people tend to ascribe purpose to their life, we pretty much all choose our life goal and ambitions and as such the purpose of our life or what we live for. For many this is in relation to God. So yes, life can have a purpose without God, but only what is given to it by humans.
As for the existence of life itself, without a Creator, it would merely be a matter of being born, living and then dying with no real ultimate purpose for that life.
And what I've unintentionally managed to do there is a typical philosophical answer, arguing both sides of the argument at once =P