Night terrors : The Last Word On Nothing: So the upshot is this: sleep paralysis is just a simple biological mistake that was never edited out during evolution because while the Old Hag is unpleasant, she has no deletrious effects on evolutionary fitness.
But hang on. It ends up being a little more complicated than that.
At nightterrors.org, a web site dedicated to helping people who suffer from these episodes, the first disclaimer is that “unlike what people have told you, this isn’t Satan.” If you’re not religious, that statement will strike you as a completely left-field nonsequitur. What does Satan have to do with any of this? And then it dawns on you that this little hiccup in the brain may have had an incredibly profound effect on human history. After all, an experience that intense, that has been shared by so many people across cultures, could account for a lot of humanity’s more inexplicable beliefs.