Two things:
1) There are NO ALIENS
YET. I put emphasis on the word "yet" because it is important and those who do not understand the meaning of that word should really look it up.
2) Accepting No. 1 above, doesn't necessarily mean that aliens do not exist--the law of probability states that the chances of aliens being out there is quite low, but it doesn't rule out the possibility that they do exist. And no one escapes statistics--aside from death and taxes, statistics will always be perennial.
-RODION