A new theory by researchers suggests that among us live the remnants of an advanced ancient human civilization that managed to survive.

In a new paper, a team of scientists from the Harvard Human Flourishing Program and Montana Tech University argue that there might be intelligent crypto-terrestrial creatures living on Earth, hidden from human eyes. They are believed to live underground or in the vicinity of our planet, for example on the Moon.

The study’s authors suggest that these intelligent crypto-terrestrial beings may in fact be responsible for many unidentified aerial phenomena typically attributed to intergalactic aliens.