It is not unreasonable to speculate that extraterrestrials have visited Earth. Our galaxy, the Milky Way, is old, very large, and has many potentially habitable planets, giving other intelligent species plenty of time to achieve very high-speed interstellar travel, with the goal of and various expeditions lasting centuries or more.
Just imagine: if an intelligent extraterrestrial species were to briefly visit Earth once every 15,000 years or so, there is no way we would know about it today. After all, the earliest writing dates back only to 3,400 BC.
But what if extraterrestrials had landed on Earth thousands of years ago, and their visit was recorded in the earliest known writings in human history? What might such a description look like? The famous astrophysicist, Karl Sagan, speculated on this very topic with his colleague Josif Shklovski in their 1966 book "Intelligent Life in the Universe".
"Such hypotheses are entirely reasonable and worthy of careful analysis. It is clear that reestablishing a contact with an extraterrestrial civilization has many difficulties. Because a simple narrative about the appearance of a strange being, who performs wonderful works and who lives in the heavens, is not enough," he wrote.
After all, ancient writings are full of fictional, folkloric accounts of deities and the supernatural. So what would make a possible story of human contact with extraterrestrials special? "Description of the morphology of an intelligent non-human being, a clear description of astronomical realities that a primitive people could not understand by their own efforts, or a transparent representation of the purpose of the contact, would increase the credibility of the legend"- Sagan pointed out.
He went on to refer to a story that fits those requirements, of course with a caveat: "I'm not claiming that the one I'm citing is necessarily an example of extraterrestrial contact, but it's the kind of legend that deserves more careful study."
He then describes the legend of Oanes of Sumer, the earliest known civilization in the historical region of Southern Mesopotamia, which flourished between 4500 and 1900 BC. Many ancient authors tell of a creature called Oanes, who appeared in a part of the Persian Gulf bordering on Babylon.
"Her whole body resembled a fish. And under the fish head was another head. The legs below were those of a man, attached to the tail of the fish" - it is further said. According to legend, Oanes gave the early Sumerians "information on letters, sciences and every kind of art".
He taught them to build houses, establish temples, compile laws, and explained to them the principles of geometrical knowledge. Other creatures similar to Oanes are mentioned in other ancient stories. They are called Apkallu.
"The Sumerian civilization is described by the descendants of the Sumerians themselves as being of non-human origin. A series of strange creatures appear over the course of several generations. Their sole purpose seems to be to guide humanity. Everyone knows the mission and achievements of his predecessors" - writes Sagan.
Notably, the Apkallu are never depicted as gods. Sagan acknowledged that talk of extraterrestrials in ancient Sumeria without the overwhelming evidence needed to substantiate such a bold claim was just speculation.
“A fully convincing demonstration of past contact with an extraterrestrial civilization will always be difficult to secure on textual grounds alone. But stories like the legend of Oanes, and the representations of the earliest civilizations on Earth, deserve much more in-depth studies than to date, with the possibility of direct contact with an extraterrestrial civilization as one of many possible alternative interpretations" - underlined Sagan . / "Big Think" - Bota.al