Proponents of the ancient astronaut hypotheses often maintain that humans are either descendants or creations of extraterrestrial intelligence (ETI) who landed on Earth thousands of years ago. An associated idea is that humans evolved independently, but that much of human knowledge, religion, and culture came from extraterrestrial visitors in ancient times, in that ancient astronauts acted as a "mother culture". Some ancient astronaut proponents also believe that travelers from outer space, referred to as "astronauts" (or "spacemen") built many of the structures on Earth (such as Egyptian pyramids and the Moai stone heads of Easter Island) or aided humans in building them.

Various terms are used to reference claims about ancient astronauts, such as ancient aliens,ancient ufonauts, ancient space pilots, paleocontact, astronaut- or alien gods, or paleo- or Bible-SETI (search for extraterrestrial intelligence).

On Thursday (June 29), a guest on Alex Jones' radio show named Robert David Steele claimed that Mars is inhabited — by people sent to the Red Planet against their will.

"We actually believe that there is a colony on Mars that is populated by children who were kidnapped and sent into space on a 20-year ride, so that once they get to Mars, they have no alternative but to be slaves on the Mars colony," Steele told Jones, the founder of the controversial InfoWars website.