Since humans made up religion, then what are these ghosts?

I believe that religion is completely man made.We assumed and imagined up a higher power, thus we named "God". So since it is man made, then why are there ghosts? From what I do no already ghosts are NOT man made, -we die and come back so to speak-. We can imagine them though and make things up as we go along. So are there truly beings in an afterlife after all? How do we know that other organisms believe in a God or ghosts as well? This is not a place to write your "believe in god" shit, so please tell me your thoughts on what ghosts are from. Thanks! :]
I do not have proof of ghosts in pictures or such but I can feel energy at some points even see it. However, I do no that there's a huge possibility to it just being imagination after all.