Yes,they exists. Because the Universe is so vast and still expanding at this very moment that even our modern studies and theories can't measure how really big it is. Our resources and knowledge are limited that we never know what is really out there. And i believe that if god created the universe to the extent where humans cant even reach the far corners of it then why would he just create only one intelligent species,Us? I strongly believe that life exists everywhere and its just a matter of time that we find other intelligent beings. And some theorist said that they believed aliens came here and visited us million years ago. One example is the pyramid itself. I believe it was never been built by humans in the first place.