God is what I call the source of life. Is it your argument that there is no "source of life"? I think it's a valid argument as to what this source is and what not but I don't think you can argue against there being a source.
I don't know if there's a "source" in the sense of a consciously creative entity, but working backwards in time it's clear that there's a long, long chain of events that got us here. The source would have to be whatever we're ultimately dependent upon -- That which, if taken away, would render our existence impossible. It could be something as simple as a quantum "blink" of subatomic matter, or something so elusive that it could take centuries to even find words
This Wikipedia article might be of interest: The AbsoluteWiki