Think in computers. It may be possible that there are alien computers that use the binary numbering system? Think on it as the DNA (oversimplifying, of course).

Think in computers. It may be possible that there are alien computers that use the binary numbering system? Think on it as the DNA (oversimplifying, of course). Now, there is any possibility that they use python as their programming language or the intel processors instruction set? That chains of DNA are interpreted in the exact same way, specially the very basic ones (i.e. how to turn sugar into energy) is what makes very improbable, or at least easy to verify, that something from here have in fact alien origin. Maybe we had 2 waves of incoming DNA from another specific planet, one that bring here the basic building blocks and another the octopus branch (that had the same way to read DNA as it have the same origin), but if that evolution could happen somewhere else, why it couldn't had happened here? The idea that their evolution could had been triggered by an alien virus still have the same origin requirement. You still have DNA that must be interpreted in the exact same way as ours to work. Occam's Razor would be useful here, just push the moment of the split from our branch closer to the point when we went from unicellular to multicellular