Aliens from Dark Earth?
Jay Alfred, in a paper entitled Aliens from Dark Earth: Evolution of Dark Plasma Life Forms on Earth posits that a concomitant Earth formed alongside the Earth we know, and the beings who evolved in this Dark Earth can account for UFOs, and other paranormal experiences.
Jay Alfred's hypothesis is a quirkier verison of Mac Tonnies' Crypto-terrestrial hypothesis.
It's an imaginative hypothesis, just as Tonnies' was, but it's a bit far out for our taste(s).
However, we have some visitors here who will find the ideas in the PDF entrancing we think...
So click here for the PDF