But how do you know this? Science fiction films have 99.9% of the time got in them exactly what you have described in your post. however science fiction is exactly what it is called, fiction. An alien presence would have to be much much further advanced than ourselves in terms of technology, because they would have been able to travel further than we can even see/hear with things like radio telescopes. Computers are far more intelligent than most humans when it comes down to speed of thinking and being able to calculate imputed commands, and technology is advancing on earth and without a doubt, computers will be thinking for themselves widespread in the foreseeable future, and they are getting smaller and smaller. what is to say human brains won't do the same in thousands of years, due to technology? What I am trying to say is, we all have this vision of how creatures from outer space will look like, but isn't that just stereotyping them. When we look at other planets outside our solar system, we look for the things we know, because we don't know about the things that we have not yet discovered to be on this planet, and certainly not on other planets or in other galaxies, therefore, we know a planet may have had water on it because we know what water is and what the signs are. Referring to P3's post, before we knew what DNA was, nobody went looking for it, because nobody knew it existed, so why should people look for other matter when they don't actually know it exists? An alien may come in a different form than an animal, who knows? We haven't seen one yet, as far as we know