A new paper suggests extraterrestrials could also be living underground or in a base inside the Moon.

The study by Harvard University’s Human Flourishing program further puts forward the idea that UFOs, or unidentified aerial phenomena (UAP), may be spaceships visiting their Earth-based alien friends.

The researchers have investigated so-called ‘cryptoterrestrials’.

These could be disguising themselves as humans to fit in, may have come from Earth’s future or might have descended from intelligent dinosaurs.

The study was created to offer an alternate “unconventional” explanation for UAP sightings and to hypothesize what they might mean, and “the possibility that UAP may involve forms of non-human intelligence (NHI) that are already present in Earth’s environment in some sense” that exist “alongside us in distinct stealth”.

The paper reads: “The author became increasingly aware of the depth of evidence and theory that also tentatively supports another ultraterrestrial explanation: the “cryptoterrestrial” hypothesis (CTH) – our focus here – which holds that UAP may reflect activities of NHIs concealed here on Earth (e.g., underground) and its environs.”

The second are hominid or theropod cryptoterrestrials: A technologically advanced non-human civilisation consisting of some terrestrial animal which evolved to live in stealth (e.g., underground). The paper suggests these could be an ape-like hominid descendant, or descendants of “unknown, intelligent dinosaurs”.