Oannes: The Fish-Man Who Bridged Two Worlds

How a Babylonian priest introduced Greek readers to Mesopotamia’s most important myth about the birth of civilization

A creature emerged from the Persian Gulf during humanity’s earliest days. Part fish, part human, it walked onto the shores of ancient Babylonia and changed everything. This being taught the first people how to write, build cities, establish laws, and worship the gods. Each evening it returned to the sea. Each morning it came back to continue its instruction.

This wasn’t just another creation myth. The story of Oannes, preserved by a Babylonian priest named Berossus around 281 BCE, represents something more profound: an ancient culture’s last effort to explain itself to conquerors who didn’t understand it.

Bas-relief (probably) of an Apkallu figure from the temple of Ninurta at Nimrud (Public domain)

Berossus lived during the aftermath of Alexander the Great’s conquest. Born around 350 BCE, he served as a priest of Bel Marduk at the Esagila Temple in Babylon and witnessed his world transform under Macedonian rule. The Greeks who now governed Mesopotamia knew little about the region’s ancient traditions and cared even less. Most relied on questionable accounts like those of Ctesias, filled with sensational stories that bore little resemblance to reality.

Berossus composed his three-volume work, the Babyloniaca, around 281 BCE and dedicated it to the Seleucid king Antiochus I Soter. His goal was straightforward: educate these new rulers about the civilization they now controlled. He had access to the temple archives, could read cuneiform tablets, and understood Mesopotamian religious traditions deeply. What he created became the primary source through which Greek and later Roman authors learned about Babylonian mythology.

The first volume opened with Oannes. In Berossus’s account, this creature appeared during the reign of the first king of Babylon and taught humans everything necessary for civilized life, including writing, mathematics, agriculture, city planning, temple construction, and legal systems. According to the description preserved by later authors, Oannes had a fish’s body with a human head underneath the fish’s head and human feet emerging below the fish’s tail.

But Oannes wasn’t Berossus’s invention. The priest was translating much older Mesopotamian traditions about beings called apkallu into Greek. In Sumerian, the first of these sages was known as Uanna, which became “Oannes” in Greek. Ancient cuneiform texts described seven of these wise beings who served as advisors to antediluvian kings.

The apkallu came from the sea and were sent by the god Ea, also called Enki, who ruled over freshwater, wisdom, and magic. Ea himself held deep symbolic importance in Mesopotamian religion. Originally worshipped in the city of Eridu as lord of the Apsu, the freshwater ocean beneath the earth, Ea evolved into a major deity associated with ritual purification, sorcery, and the arts.

Eridu itself carried enormous weight in Mesopotamian consciousness. Founded around 5400 BCE, the ancient Sumerians considered it the first city in the world, created by the gods as the starting point for establishing order on earth. The city was Ea’s home, and its great temple, the E-Abzu, stood as one of the most important religious sites in southern Mesopotamia for thousands of years.

Ziggurat at Eridu (CC BY 2.0)

The fish imagery surrounding Oannes and the apkallu wasn’t arbitrary. These beings emerged from water, specifically from the realm of Ea. Neo-Assyrian palace reliefs from the ninth and eighth centuries BCE show protective figures wearing elaborate fish-skin cloaks, their human forms draped in the bodies of fish. These depictions appear prominently in constructions from the reign of Ashurnasirpal II and continued through later periods.

Ordinary Mesopotamians placed images of the apkallu in their homes as protective amulets. The sages represented divine wisdom made tangible, guardians against evil and chaos. Kings invoked them in inscriptions and rituals. Their presence connected human civilization to cosmic knowledge passed down from the gods through Ea.

Berossus’s narrative emphasized something crucial: Oannes didn’t just share random information. The creature taught humans “all those things conducive to a settled and civilized life,” and according to Berossus, since that time nothing further had been discovered. This wasn’t about incremental progress. It was about a complete transmission of knowledge, a moment when civilization itself came into being.

Cylinder Seal: God Ea standing on a fish man and a goat fish. Source: hermitagemuseum

After Oannes, more apkallu appeared. Berossus described several more fish-creatures coming to humanity during the reigns of subsequent kings, repeating what Oannes had taught but adding nothing new. Then came the flood, and the world changed. Post-deluge sages were human rather than divine, though they still carried wisdom from the gods.

The story reached Greek audiences through complicated channels. Berossus wrote in Greek, but his command of the language was imperfect. Modern scholars note that his text wasn’t written in proper Greek style but was essentially a transliteration of Mesopotamian myths. This rough translation actually helped preserve authentic details that might have been lost if he’d adapted the stories more thoroughly for Greek tastes.

Most pagan writers never read Berossus’s original work directly but relied on an epitome, an abridged version, created by the first-century writer Alexander Polyhistor. Later, Christian authors like Eusebius and Josephus quoted extensively from these summaries. The Babyloniaca itself is lost, but these fragments survived, carrying Berossus’s account of Oannes across the centuries.

The Greek world didn’t embrace Berossus enthusiastically. His work had little impact on contemporary Hellenistic culture, which preferred more rationalistic accounts and had little use for creation myths involving gods instructing humans. Greeks prided themselves on human-centered explanations of history, not divine intervention stories. Besides, Berossus’s awkward Greek made his work difficult for educated Greek readers.

But preserved in those fragments is something remarkable: a window into how Mesopotamians understood their own origins. The story of Oannes wasn’t just about a fish-man teaching primitive humans. It encoded deeper beliefs about the relationship between divine knowledge and human civilization, about the role of water as a source of wisdom and life, about the moment when chaos became order.

Modern archaeological discoveries have strengthened Berossus’s credibility. During the 1970s, a German expedition discovered cuneiform texts in Uruk with a regnal list similar to what appears in the Babyloniaca’s second book. This finding confirmed that Berossus had quoted authentic ancient sources, not simply invented stories to impress his Greek patrons.

The Uruk List of Kings and Sages, dating to 165 BCE, matches Berossus’s account fairly well. It pairs seven antediluvian kings with their associated sages, then notes the deluge, then continues with post-flood rulers and their human advisors. The first king, Alulim, corresponded to the time when Oannes appeared, just as Berossus had written.

Cuneiform tablet showing king list. (Public domain)

What makes Oannes significant isn’t whether the story is literally true. It’s what the story reveals about how an entire civilization understood knowledge itself. For the Mesopotamians, wisdom didn’t emerge from human trial and error alone. It came from the gods, mediated through special beings who bridged the divine and mortal realms. The apkallu stood between worlds, carrying cosmic understanding down to earth.

This contrasts sharply with Greek intellectual traditions, which increasingly emphasized human reason and discovery. Greeks told stories about Prometheus stealing fire from the gods or about human heroes achieving greatness through their own efforts. Mesopotamian myths stressed divine gifts and the importance of maintaining proper relationships with cosmic forces.

Berossus tried to bridge these different worldviews. He was a priest of an ancient tradition writing for a new audience that didn’t share his culture’s assumptions. The fact that his work survived at all, even in fragments, suggests it filled a need. Some Greeks and Romans wanted to understand this older civilization, wanted to access its accumulated wisdom, wanted to know the stories that had sustained cultures for thousands of years.

The fish-cloaked figures on Assyrian palace walls, the stories of sages emerging from the sea, the traditions about Eridu as the first city where Ea taught humanity, the complex mythology surrounding divine wisdom and human civilization all of this came down to later ages primarily through Berossus’s imperfect Greek prose.

E-abzu temple of Eridu (CC BY-SA 3.0)

When we read about Oannes today, we’re seeing ancient Mesopotamia through multiple layers of transmission. The original Sumerian traditions about Uanna and the apkallu. Those traditions as they evolved in Babylonian culture. Berossus’s translation of those traditions into Greek. Alexander Polyhistor’s epitome of Berossus’s work. The quotations preserved by Eusebius and Josephus. Each layer adds complexity, but also each layer represents someone trying to preserve and pass forward knowledge they considered important.

The creature that walked out of the Persian Gulf in the time of the first kings carried more than practical skills. It carried the idea that civilization itself required divine sanction, that knowledge connected the human and cosmic realms, that wisdom was something received rather than simply discovered. These beliefs sustained Mesopotamian culture through millennia of change.

Berossus’s account of Oannes represents a moment of cultural translation, an attempt to explain one civilization’s foundational myths to conquerors from another civilization. That such efforts were made at all speaks to something fundamental about human culture: the desire to be understood, to have one’s traditions recognized as meaningful, to ensure that knowledge accumulated over centuries isn’t simply lost when power shifts.

The story of Oannes survived because people kept telling it, kept writing it down, kept thinking it mattered. From cuneiform tablets in temple archives to Greek epitomes to Christian chronicles, the fish-man who taught humanity kept appearing in new contexts, adapted but recognizable. A Babylonian priest gave this ancient tradition its most famous form when he wrote for a Greek king, creating a bridge between worlds that would outlast both empires.