When people say that you can't prove there is no god they can only say that by being as vague as possible about the words "prove" and "god". Define "god" and of course we can prove it is nothing but a human construct.
Take god and religion out of the discussion and instead replace it with intelligent design. It seems many think that intelligent design automatically equates to a god of any past belief, as if it's not one of those then there is no other possibility. If you still want the word there, I'll define god as, "the conscious intelligence that engineered life on Earth". I believe genetic engineering alone proves this to be a possibility. I completely dismiss the excuse that if it was another biological form that created "Earth life" that doesn't answer the origin of their life, etc,etc. It doesn't matter if "our" origin is the start of it all or further on the chain, if there is a chain, you must move up it to get to the original source. Ignoring parts if they turn to be true because it doesn't reach the final answer looked for just means you'll never move up the chain.