Proponents argue that the evidence for ancient astronauts comes from documentary gaps in historical and archaeological records, and they also maintain that absent or incomplete explanations of historical or archaeological data point to the existence of ancient astronauts.
According to astrophysicist Carl Sagan, "In the long litany of 'ancient astronaut' pop archaeology, the cases of apparent interest have perfectly reasonable alternative explanations, or have been misreported, or are simple prevarications, hoaxes and distortions".
Paleocontact or "ancient astronaut" narratives first appeared in the early science fiction of the late 19th to early 20th century. Wilkins in 1954; it received some consideration as a serious hypothesis during the 1960s; and has been mostly confined to the field of pseudoscience and pop culture since the 1970s.
to arguments that scientists and historians should seriously consider the possibility that extraterrestrial contact occurred during recorded history.
However, Shklovski and Sagan stressed that these ideas were speculative and unproven.
Shklovski and Sagan argued that sub-lightspeed interstellar travel by extraterrestrial life was a certainty when considering technologies that were established or feasible in the late '60s; and that pre-scientific narratives can offer a potentially reliable means of describing contact with alien.