Hipótesis criptoterrestre

Inteligencias no humanas que ya habitarían la Tierra, ocultas, en vez de venir de otro planeta.

The cryptoterrestrial hypothesis proposes that reports of flying saucers or UFOs are evidence of a hidden, Earth-based, technologically advanced civilization. Aaron John Gulyas, a scholar of conspiracy theories, characterized the hypothesis as "really more of a thought experiment designed to raise questions", while others note that "even people open to the cryptoterrestrial hypothesis remain skeptical".