In 1966, famed science communicator Carl Sagan and his Soviet colleague Iosif Shklovsky released a book titled Intelligent Life in the Universe. The book remains one of the most highly influential books on the subject of extraterrestrial intelligence.
When discussing possible consequences of direct contact, they note that scientists must take the possibility that extraterrestrials have visited Earth in the past seriously. They also note that evidence of past contact could be preserved in the folklore and mythological traditions of various cultures.
As an example, Sagan and Shklovsky point to an account of the contact made between the Tlingit people of the Pacific Northwest and the La Perouse French expedition in 1786. This event was recorded a century later by anthropologist G.T. Emmons during one of his many visits to the area.
While the account was told in the context of Tlingit mythology and contained supernatural elements (for example, the sailing ships were described as immense black birds with white wings), the descriptions left no doubt that it was a faithful retelling of an actual event. Sagan and Shlovksy wrote that the same could be true of extraterrestrials visiting Earth in the past:
"The encounter between La Perouse and the Tlingit suggests that under certain circumstances, a brief contact with an alien civilization will be recorded in a reconstructible manner. The reconstruction will be aided if (1) the account is committed to written record soon after the event; (2) a major change is effected in the contacted society by the encounter; and (3) no attempt is made by the contacting civilization to disguise its exogenous nature."
Of course, Sagan and Shklovsky emphasized the need for skepticism and stated that these ideas were speculative and unproven. This was in large part because of some rather wild and unscientific theories that had become popular by the late 1970s. These would come to be known as "Ancient Astronaut" theories, which are no less popular today.
Pyramids, Paleo-Contact, and Alien DNA
To break it down, the Ancient Astronauts (AA) theory is that extraterrestrial intelligence has visited Earth in the past and made contact with ancient humans. In some cases, proponents maintain that contact played a role in our technological, cultural, or spiritual evolution.
Some argue that aliens were responsible for (or assisted in) the construction of ancient monuments and structures. In specific cases, it is argued that these monuments paid homage to alien species, whom ancient people viewed as gods. This version of the AA hypothesis has become rather popular, as illustrated by the History Channel series Ancient Aliens.
Meanwhile, other proponents of the AA theory insist that humans are actually descendants (or creations) of aliens and that they altered the DNA of ancient primates in order to foster intelligence in hominids (what could be called "Geneticists").
People who subscribed to this school of thought argue that modern humans are the result of genetic alteration by a more advanced species. Variations of this argument include claims that aliens contributed their own genetic material to fast-track human evolution or that humans are the descendants of alien colonists.
Origin and Influence
While examples of the AA theory and paleo-contact can be found in science fiction works as early as the late 19th century, it was not until the mid-20th century that it began to be argued as an actual theory. In 1954, British pseudohistorian Harold T. Wilkins proposed that UFO abductions have occurred since ancient times.
In 1960, Louis Pauwels and Jacques Bergier (two French journalists and conspiracy theorists) released The Morning of the Magicians, which merged elements of pseudohistory and occultism with theories about UFO, conspiracies, and ancient astronauts.
French science-fiction author Robert Charroux also wrote about ancient astronauts in his 1963 book, One Hundred Thousand Years of Man's Unknown History, along with theories of lost continents (Atlantis, Mu, Hyperborea), UFOs, and apocalyptic prophecies.
But it was Erich von Däniken, the well-known Swiss author and fraudster, who popularized the AA theory (as it is commonly known today) with his 1968 book Chariot of the Gods?. In this and subsequent books, von Däniken established arguments cited by AA theorists to this day.
Among the many arguments made by von Däniken was that extraterrestrials were responsible for some of the greatest technological innovations in the ancient world and that the evidence for this can be found in ancient structures and artifacts.
In particular, von Däniken claimed that these structures were built using methods and technology which could not have been available to the indigenous culture at the time. Examples include the pyramids of Giza, Stonehenge, Pumapunku, the Moai of Rapa Nui, the Nazca lines of Peru, and the "Baghdad batteries."
Däniken further argued that ancient artwork and iconography depict spacecraft, extraterrestrials, and advanced technology. These include the Japanese Dogū figurines that he claimed resembled astronauts, the "helicopter hieroglyphs" in the Egyptian temple of Seti at Abydos. The fact that disparate cultures had common elements in their artwork was also cited as evidence.
Last, but not least, he claimed that many ancient religions (Egyptian, Mesopotamian, Hinduism, etc.) were inspired by paleo-contact. Däniken referred specifically to instances where ancient people refer to "chariots in the sky," and other divine revelations were actually instances where humans communicated with aliens.
Despite being panned by academics everywhere, von Däniken's book would prove to be influential and would inspire a number of similar books that were published throughout the 1970s. These included Zecharia Sitchin's The 12th Planet (1976), in which he argued that the ancient Sumerians were descended from aliens from a planet called Niburu.
Sitchin claimed that this planet orbits the Sun at a great distance and takes 3,600 years to complete a single orbital cycle. He based this on his personal interpretations of Sumerian and Middle Eastern texts, which he claims mention a “12th planet” associated with the Babylonian god Marduk (who was later astrologically associated with Jupiter).
Also released in 1976 was Robert K. G. Temple’s The Sirius Mystery, which argued that the oral traditions of the Dogon people of West Africa include a description of paleo-contact. According to Temple, contact took place between the locals and an advanced species from Sirius roughly 5000 years ago.
Dogon also credited this alien species with inspiring the mythological traditions of Mesopotamia, Egypt, Greece, and other cultures. These theories remained popular with counter-cultural groups during the 1970s and were often embraced as part of new-age spiritualism and fascination with ancient cultures.
By the early 1980s, interest in the AA theory began to wane, but in recent decades, it has experienced something of a renaissance. Thanks to the proliferation of conspiracy-theory websites, non-academic publications, and television series' featuring these theories, it has become popular again since the late 1990s.
Evidence? What Evidence?
Proponents of AA theory rely on a combination of oral traditions, literary references, bits of archaeology, cultural similarities, and gaps in historical/archaeological records to support their arguments. For example, von Däniken's biggest claim is that ancient cultures did not have the sophisticated technology needed to create structures and artifacts.
Another line of "evidence" are ancient texts that make reference to the gods, which von Däniken claims were actually advanced extraterrestrials. In Chariot of the Gods?, he cites passages from the Sanskrit epic Ramayana, where the gods travel to and fro on flying chariots called "Vimana" (which he claimed was a reference to spacecraft).
Sitchin's theories, meanwhile, are based entirely on his reading of the Babylonian creation myth, Enûma Eliš. Specifically, he claims that the Annunaki (the most powerful and important gods in the Babylonian pantheon) were a technologically advanced race of humanoids from the planet Niburu.
According to Sitchin, Niburu is an undiscovered planet beyond Neptune that has a highly elliptical orbit, causing it to enter the Solar System once every 3,600 years. Niburu is the "12th planet" in Sumerian mythology, Sitchin argued, because they counted the Sun and Moon as planets (this list also included Pluto).
Sitchin further claimed that Niburu (the name was later changed to Marduk, he claims) collided with another planet located between Mars and Jupiter (aka. the Asteroid Belt). This planet was known as Tiamat (a goddess in the creation myth that was overthrown by Marduk), the debris of which formed planet Earth.
He claims that they first arrived on Earth probably 450,000 years ago, looking for minerals (especially gold) which they grew tired of mining. Hence, they created a slave race (humans) by combining their DNA with that of Homo Erectus. Sitchin further claimed that these accounts coincide with biblical texts.
According to Temple, there are similarities between the mythological traditions of the ancient Sumerians, Egyptians, Greeks, and those of the Dogon people in West Africa. These include shared myths, symbols, and ideas, as well as the advanced astronomical knowledge, which he claims is evidence of paleo-contact.
Proponents like Giorgio Tsoukalos, a former sports commentator and current consulting producer on Ancient Aliens, even venture that extraterrestrials were responsible for causing the Cretaceous–Paleogene extinction event (which killed the dinosaurs) as part of an attempt at directing evolution.
Science Fact vs. Fiction
If this is starting to sound familiar, it's probably because the idea is quite popular in science fiction circles. The classic example (and gold standard) was the 1968 film 2001: A Space Odyssey, a film that depicts a highly-advanced ETI coming to Earth in the past and our attempts to meet up with them in the near future.
This film was the work of esteemed writer/director Stanley Kubrik and famed science communicator Arthur C. Clarke. It was also inspired by two short stories written by Clarke: "Encounter in the Dawn" (1953) and "The Sentinel" (1951).
These stories were the basis for Parts I and II of the film. The former part takes place millions of years ago, where extraterrestrials visit Earth at a key point in humanity's evolution. The latter part occurs around the turn of the century, when humanity uncovers an alien artifact on the surface of the Moon.
Other examples include an episode of Star Trek: TNG (S6E20, titled "The Chase"). In this episode, the crew discovers that an ancient predecessor race was responsible for the creation of life in their quadrant (hence why just about every species in the galaxy are humanoids!)
Fans of Stargate (the 1994 movie and the series' that followed) ought to instantly recognize how this franchise was built on a foundation of AA theory. The story centers on how paleo-contact between early humans and an ancient species (the Goa'uld) led to the birth of Egyptian civilization, and how their gods were actually the Goa'uld themselves.
A more recent example is Prometheus, the 2012 film by Ridley Scott that was clearly inspired by 2001: A Space Odyssey. This film shows how an ancient race of "Engineers" (aka. the "Engineers" or "Space Jockeys" from Alien) was responsible for creating humanity, as well as the xenomorph that is the franchise's main antagonist.
The idea remains popular for obvious reasons. It's a fascinating concept that touches on multiple scientific theories and pursuits, not the least of which is panspermia, the search for extraterrestrial intelligence (SETI), the Fermi Paradox, and abiogenesis (the origins of life).
But in the hands of people like Däniken and other AA theorists, it quickly became recognized as something somewhere between new-age spiritualism and pseudoscience. As expected, the reception Däniken's book got from the academic community was resoundingly negative.
Pseudoscience or Veiled Racism?
Whether it was archaeologists, paleontologists, anthropologists, astronomers, SETI-researchers, geneticists, biologists (the list goes on), there was no shortage of lining up to offer harsh critiques about his theories, his research methodology, and his conclusions.
Sagan and Shklovksii were two such individuals. In fact, Sagan wrote in his 1979 book Broca's Brain that he and Shklovskii regretted whatever role they played in the 1970s ancient astronaut craze. Sagan specifically referred to von Däniken "and other uncritical writers" who offered their theories up as unsubstantiated proof rather than food for thought.
On its face, AA theories are easy enough to debunk because of their lack of evidence, sloppy research, confirmation bias, falsifiable premises, and disprovable claims. Chief among these is the claim that ancient peoples were not capable of creating ancient monuments and megalithic structures.
Archaeologists have challenged this by demonstrating with evidence the methods used by the Egyptians, Incas, Mesoamericans, Mesopotamians, and other cultures. In all cases, it was a simple matter of having the right materials, basic tools, an understanding of engineering and geometry, and thousands of laborers - all of which these empires possessed in abundance!
In addition, academics have debunked AA claims that megalithic structures appeared suddenly by pointing to the archaeological record (or even historical records). For example, in Peru, archaeologists discovered evidence of rope-and-lever systems that were used by the Inca to transport stones to build the fortress of Sacsayhuamán north of their ancient capital of Cusco.
Similarly, the Incan Nazca Lines were made in a way that was similar to how other geoglyphs around the world were, by simply removing the darker top layer of the ground to expose brighter patches beneath. They were also easy enough to plot out using simple measurements and a hillside viewing - i.e., they did NOT require aircraft to appreciate!
In the case of the Egyptian pyramids, archaeologists have been able to construct a detailed account of how (and even why) they were built. This includes locating the quarries where the stone came from, what tools were used, what engineering techniques were involved, and even written records that describe their purpose and how the labor was organized.
In short, the "gaps" in the record that AA theorists refer to are actually gaps in their own knowledge. This is a classic example of the appeal to ignorance fallacy, where a supposed lack of evidence to the contrary is considered proof.
Another common logical fallacy that comes up in AA theory is the analogy known as “Russell’s teapot.” Essentially, many AA theorists have argued that their ideas cannot be disproven whenever they are criticized for not meeting the burden of proof.
Yet another poignant criticism of AA theories is the way they resemble racist and ethnocentric theories regarding cultural sites around the world. Between the 16th and 19th centuries, European explorers observed a number of megalithic structures in Africa, Asia, and the Americas for the first time and misattributed their origins.
In short, they often concluded that the local population was not capable of creating such feats of construction and engineering. A classic example of this is Angkor Wat, a series of ancient structures in modern-day Cambodia that covers an area that measures about 155 mi2 (400 km2).
These ruins were once the capital of the Khmer Empire (ca. 9th to the 15th century) that stretched across much of South-East Asia. However, when French naturalist Henri Mouhot first observed the temples in 1860, he theorized that it must have been built by the ancient Romans or Alexander the Great, because he assumed the indigenous Khmer were incapable.
Similarly, you have the large earthen mounds at Cahokia, Illinois (the largest of which is known as Monks Mound), which were built in 1050 CE by the Mississippian culture. Before the city declined by 1400 CE, it supported a population of 25,000 to 50,000 people who cultivated maize, hunted with fine arrow points, and created pottery, shell jewelry, and flint clay figurines.
But after white missionaries and settlers began moving to the area by the 17th century and after, they denied that local people were responsible. Some went so far as to claim that it was travelers from Egypt or elsewhere that were responsible. Similar claims have been made about the stepped pyramids of Mesoamerica, such as the Chichen Itza, Teotihuacan, and others.
Once again, the notion that traveling Egyptians design or built these structures (rather than the Mayans, the Toltecs, Aztecs, and other local peoples) remains a popular one even to this day. This is in spite of the fact that archeologists have thoroughly debunked them using archaeological evidence, carbon dating, and other methods.
While carbon dating has shown that the Egyptian and American pyramids were built thousands of years apart, archaeological evidence shows that different methods were used to build them. It's also been demonstrated that they served different purposes, where the great Pyramids were tombs for the pharaohs while Mesoamerican stepped pyramids were associated with religious rites.
On top of all that, with the exception of the Viking expeditions, no evidence exists of trans-Atlantic contact prior to the "Columbian Era" (late 15th/early 16th centuries). At their core, AA theories are all come down to the Eurocentric belief that only cultures from the Mediterranean or West Asia (where modern western history traces its roots) were capable of megalithic engineering.
In this respect, AA theories are much the same, except that aliens have become a substitute for European or Mediterranean civilizations! At the end of the day, it is just assumed (without evidence) that indigenous human beings weren't up to the task.
Perhaps another reason why AA theories remain popular is that they appeal to a sense of wish-fulfillment. After all, the idea that advanced extraterrestrial civilizations exist out there and have visited Earth before is intriguing! So maybe it's not all racism and conspiracy-theories. That does not change the fact that these beliefs are built on the rejection of the scientific method.
Worse than that, it denigrates our own ancestors by denying their accomplishments. On its own, believing that intelligent life exists elsewhere in the Universe sounds like a positive thing. But not when it causes us to lose sight of our fellow humans and the undeniable spark of creativity we all possess.
Sometimes, we need to let that spark grow into a full-fledged fire, then express it through massive works of art, architecture, and engineering. As for the engineering, construction, and technical details, we'll figure that out with the tools and knowledge we currently have.