Most likely ghosts. The reason why we could be statistically the only planet with life is that the statistical chance of even this planet existing is one in seven-hundred quintillion (twenty zeros) and therefore would be just as unlikely to find another planet like our own. The paranormal seems to make more sense because we are positive that we all die and therefore it is open to discussion. We have not the slightest clue of life elsewhere. You may be saying to yourself "Is this guy really telling me that we don't know about life on other planets, but he claims that we know about life after this one?" Well, we may pass on to other places because there is religious belief dating back to ancient times thousands and thousands and thousands of years ago writing about the dead passing on and with the substantial amount of evidence both from my own life and others I have read about or heard about, I can draw an educated conclusion that the paranormal is much more likely to exist.