These are interesting thoughts. I would be keen to hear what you think might be more plausible in your eyes. I am not sure the first 2 are as valid as the later 2. I put it forward that the paradox still probably stands as we know it today. The third would be putting a human centered ethic onto an alien race; see elephant and ant argument. The forth would be interesting but as there only seems to be one path that we have all evolved from rather than disconnected paths, does it seem plausible that aliens would run a 4 billion year experiment?