Honestly, there's no way we can know. Personally, I'm open to the thought--but I'm skeptical that they exist.
"We spend most of our time and energy in a kind of horizontal thinking. We move along the surface of things [but] there are times when we stop. We sit still. We lose ourselves in a pile of leaves or its memory. We listen and breezes from a whole other world begin to whisper." ~James Carroll