But WHY? If owl done concedes to your idea of a benefactor, how long till you're trying to steer that person towards the god of the bible?
Besides... The oxygen/carbon ratios have changed many times through history. Just because our air is food for us now doesn't mean if air was a bit different, we couldn't have evolved to breathe that air perfectly. How things fit together is not evidence of any creator, just of our evolution working properly. Evolution didn't need someone to help it start, because by its very nature it makes things work out or die.
In summary, your question is pointless. Good try, keep thinking and searching. The truth is right under your nose