Jingszo !

The paper introduces the term "cryptoterrestrials" to refer to an ancient human culture—more technologically advanced than our own—that survived the cataclysms and has lived since in hiding.

A speculative new paper suggests that advanced "cryptoterrestrials" could be living secretly on Earth or in its near environs, like the moon.

It suggests the existence of a bizarre group of "intelligent beings concealed in stealth here on Earth (e.g., underground), and/or its near environs (e.g., the moon)." 

The study has been accepted for publication in Philosophy and Cosmology.