The serpent is not a necessarily a snake as we know them today, but more like a walking, talking Dragon, akin to the Dragon of Marduk, a creature that the Israelites in exile would have been very familiar with.
This was a famous icon on Ishtar’s Gate in ancient Babylon and there’s a connection with this same “serpent”/dragon in the Old Testament story Bel and the Dragon.
Dragons were worshiped all over the near-east and their appearance in Genesis may reflect the idea that these legendary creatures existed since time immemorial.
Like Walter Mattfeld writes in Eden’s Serpent: It’s Mesopotamian Origins:
“Since 1854 various scholars employing a rationalist, humanist and anthropological point of view have suggested that motifs appearing in the Genesis’ mythical Garden of Eden account appear to be recasts of earlier Mesopotamian themes and I am in agreement with this scholarly analysis [but] it is quite clear that in many cases the Hebrews were not interested in preserving Mesopotamian beliefs, rather their aim seems to have been to refute, challenge, and deny these beliefs.”
Thus, in seeking parallels, we should not expect to find an exact 100% match of details, concepts, or morals being derived because all this is being transformed into a system of Israelite belief that repudiates for the most part earlier Mesopotamian concepts and worldviews.
The writer Eve Wood-Langford reflects on how the serpent-dragon motif was viewed in its time:
“Stories surrounding Gilgamesh circulating in Mesopotamia in that age told of … a serpent-guardian of the Tree of Life (Ningishzida)… This fertility god, a doorkeeper of the sky-god, or high god Anu, is sometimes depicted as a serpent with a human head…
Whether or not Ningishzida “Lord of the Tree of Life” mentioned in Gilgamesh was a template for the articulate serpent in Eden, the serpent-image depicted in much of the ancient world… was so widely accepted as a symbol of wisdom, fertility and guidance, that polytheist populations are unlikely to have understood it as an influence for evil.”
Despite this positive view of walking, talking serpent-dragons (or maybe because of it?) there exists curious parallels between Ningishzida and the so-called serpent of Eden. Mattfeld again:
“Ningishzida is portrayed in art as having the ability to assume two forms: Human and a four-legged, horned and winged serpent-dragon. He is at home in three locations, the Edin of Sumer in Lagash [Edin being the sumerian word for the steppe land between the two rivers]; the Underworld; and Heaven, as a gate-guard for Anu. He thus has serpent associations similar to those possessed by Christianity’s Satan, who in the book of Revelation is called a serpent, dragon and devil (Rev. 20:2) who is portrayed as at home in Heaven, Eden, and the Underworld.”
Russell Gmirkin explains in his Berossus and Genesis, Manatho and Exodus:
“The idea of a serpent with legs may have derived from the sirrush or dragon that was the patron of Babylon… That the treacherous walking serpent of Genesis so closely resembled the dragon of Babylon, and was later condemned to crawl in the dust for his role in events in Eden, may reflect yet further polemics against Babylon.”
But even to Gmirkin, these motifs aren’t limited to just anti-Babylonian polemics. He too agrees that there’s a greater mythological reversal in Genesis, this time when comparing the narrative of Oannes, the walking, talking fish monster who offers “divine knowledge” to mankind:
“Berossos says that this monster spent its days with men, never eating anything, but teaching men the skills necessary for writing and mathematics and all sorts of knowledge: how to build cities, found temples, and make laws… in short, it taught men all those things conducive to settled and civilized life…
The apkallu Oannes may be suggested as the prototype for the wise serpent of Gen 3. If so, Gen 3 contains polemics against Oannes: the benevolent apkallu Oannes, sent to humankind by the gods with the gift of knowledge, has been transformed into a figure of treachery and evil, much as knowledge itself has been transformed from a blessing into a curse.”
Finally, it’s thanks to our friendly fish-monster Oannes—also named Adapa!—that we find the closest parallel to the Adam & Eve narrative: The Myth of Adapa and the Southwind. Ultimately, Adapa and the Southwind’s function is partly to explain why humans have wisdom but not immortality, and the apkallu Adapa is viewed as a precursor to the fish-monster Oannes. Without going too much into the plot of Adapa, there exist many of these aforementioned symbolic “reversals”, here’s Mattfeld again:
“Paradoxically, Enki, who played the role of Yahweh-Elohim in warning man “not to eat or he would die,” also plays the role of the serpent in that he allowed man (Adapa) to obtain forbidden knowledge and it is Enki who misrepresents to man the actions of Anu, Ningishzida, and Dumuzi, like Eden’s serpent misrepresented God’s actions and intentions.
So in the Adapa and the Southwind myth we have four gods whose actions have been fused together, recast, transformed, and assimilated to Eden’s serpent: Ea, Anu, Ningishzida, and Dumuzi (Tammuz). For me the Hebrews are giving ‘new twists’ to the earlier myths… via a series of 180 degree inversions.”
Therefore what seems to be happening is that the dragon>snake character is a recast plot device from well-known Mesopotamian narratives—except in this case reimagined and somewhat demythologized to serve the needs of the Israelite storytellers.