As an atheist, this has nothing to do with my non belief in any gods. Secondly, I am not a geneticist nor a biologist. Why you would ask a question like this in a religion section is beyond me. As far as I know, you are asking about Abiogenesis, a thing of which neither one of us apparently has any specific knowledge. This is rather curious.
The answer is, I don't know and neither do you. Saying god is the answer to where life came from does not answer any questions, it just creates a whole bunch more questions. What I do know is that scientists and biologists, (people with specific knowledge who are studying these things) are working on the question. They have done some experiments that seemed to produce the building blocks of life, but no specific thing yet. This does not mean that they will never know or that they can never know the answer to that particular question. All the theists have is god done it. And again, that does not answer anything. How do you explain that one?