Some writers have proposed that intelligent extraterrestrial beings

Extraterrestrial life

Extraterrestrial life is defined as life that does not originate from Earth...

 have visited Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 in antiquity

Ancient history

Ancient history is the study of the written past from the beginning of recorded human history to the Early Middle Ages. The span of recorded history is roughly 5,000 years, with Cuneiform script, the oldest discovered form of coherent writing, from the protoliterate period around the 30th century BC...

 or prehistory

Prehistory

Prehistory is the span of time before recorded history. Prehistory can refer to the period of human existence before the availability of those written records with which recorded history begins. More broadly, it refers to all the time preceding human existence and the invention of writing...

 and made contact with humans. Such visitors are called ancient astronauts or ancient aliens. Proponents suggest that this contact influenced the development of human culture

Culture

Culture is a term that has many different inter-related meanings. For example, in 1952, Alfred Kroeber and Clyde Kluckhohn compiled a list of 164 definitions of "culture" in Culture: A Critical Review of Concepts and Definitions...

s, technologies

Technology

Technology is the making, usage, and knowledge of tools, machines, techniques, crafts, systems or methods of organization in order to solve a problem or perform a specific function. It can also refer to the collection of such tools, machinery, and procedures. The word technology comes ;...

 and religion

Religion

Religion is a collection of cultural systems, belief systems, and worldviews that establishes symbols that relate humanity to spirituality and, sometimes, to moral values. Many religions have narratives, symbols, traditions and sacred histories that are intended to give meaning to life or to...

s. A common variant of the idea is that deities

Deity

A deity is a recognized preternatural or supernatural immortal being, who may be thought of as holy, divine, or sacred, held in high regard, and respected by believers....

 from most, if not all, religions are actually extraterrestrials, and their technologies were taken as evidence of their divine status.

These proposals have been popularized, particularly in the latter half of the 20th century, by writers such as Erich von Däniken

Erich von Däniken

Erich Anton Paul von Däniken is a Swiss author best known for his controversial claims about extraterrestrial influences on early human culture, in books such as Chariots of the Gods?, published in 1968...

, Zecharia Sitchin

Zecharia Sitchin

Zecharia Sitchin was an Azerbaijani-born American author of books promoting an explanation for human origins involving ancient astronauts. Sitchin attributes the creation of the ancient Sumerian culture to the Anunnaki, which he states was a race of extra-terrestrials from a planet beyond Neptune...

, Robert K. G. Temple

Robert K. G. Temple

Robert K. G. Temple is an American author best known for his controversial book, The Sirius Mystery which presents the idea that the Dogon people preserve the tradition of contact with intelligent extraterrestrial beings from the Sirius star-system...

, David Icke

David Icke

David Vaughan Icke is an English writer and public speaker, best known for his views on what he calls "who and what is really controlling the world." Describing himself as the most controversial speaker in the world, he has written 18 books explaining his position, and has attracted a substantial...

 and Peter Kolosimo

Peter Kolosimo

Peter Kolosimo, pseudonym of Pier Domenico Colosimo was an Italian journalist and writer. Together with the later Erich von Däniken, he is ranked amongst the founders of pseudoarchaeology .Born in Modena, he lived in Bolzano for much of his life...

, but the idea that ancient astronauts actually existed is not taken seriously by most academics, and has received little or no credible attention in peer review

Peer review

Peer review is a process of self-regulation by a profession or a process of evaluation involving qualified individuals within the relevant field. Peer review methods are employed to maintain standards, improve performance and provide credibility...

ed studies.
Ancient astronauts have been widely used as a plot device

Plot device

A plot device is an object or character in a story whose sole purpose is to advance the plot of the story, or alternatively to overcome some difficulty in the plot....

 in science fiction

Science fiction

Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...

.
Proponents of ancient astronaut theories often maintain that humans are either descendants or creations of extraterrestrial

Extraterrestrial life

Extraterrestrial life is defined as life that does not originate from Earth...

 beings who landed on Earth thousands of years ago.