Is it the common understanding that all life on earth shares a common origin and ancestor? Even methane metabolizing bacteria? How do we know life didn't spring up in a common way in separate places or times? Okay that's awesome. Is it possible that there's just one way that DNA works, though? Maybe I'll be sounding like a stoic philosopher here, but perhaps there is a natural tendency for amino acids that form to eventually make up DNA segments as we know them. So the reason the DNA is similar is because that's just the only way/best way live works? 