Uncanny science: what if another biosphere exists alongside our own, quiet and hard to discern? Naturally it lives in epistemological darkness, and receives the Infocultish name of "the shadow biosphere". And its inhabitants are “weird life”.
How could this work? The possibilities of our biological bases:
“All the micro-organisms we have detected on Earth to date have had a biology like our own: proteins made up of a maximum of 20 amino acids and a DNA genetic code made out of only four chemical bases: adenine, cytosine, guanine and thymine,” says Cleland. “Yet there are up to 100 amino acids in nature and at least a dozen bases. These could easily have combined in the remote past to create lifeforms with a very different biochemistry to our own. More to the point, some may still exist in corners of the planet.”
Hard to tell if this is speculation or pseudoscience, but it's a fun concept.
(thanks to Jesse Walker)