I’m always on the lookout for good examples of religious syncretism and wanted a good place to store these.
Lôtān -> Leviathan
In Psalm 74, verse 14, Yahweh is described as having defeated a sea monster called Leviathan. This sea creature, its name, and its mythology derive from a Ugaritic sea monster named Lôtān, who was similarly defeated by Hadad, a god in Canaanite and Mesopotamian religions. This is a clear case of Jewish religion incorporating earlier Canaanite and Mesopotamian beliefs.
Sargon of Akkad birth story -> Moses birth story
Sargon of Akkad, was the first ruler of the Akkadian Empire in the 24th to 23rd centuries BCE. Per a 7th century BCE Neo-Assyrian text purporting to be Sargon’s autobiography, Sargon was claimed to the illegitimate son of a priestess who put him as an infant in a basket of rushes sealed with tar and set him afloat in a river. He, of course, was found and raised, eventually becoming a great leader. This text may not be a direct antecedent of the biblical myth of Moses (Exodus 2) similarly being put into a basket of reeds that was sealed with tar and set afloat in the river but rather may have simply been a common archetype from the time period that served as the basis for multiple origin stories. Either way, it is a clear example of religious syncretism.
Virgin Births (or god impregnations) – Perseus, Oenopion, Romulus and Remus -> Jesus
The suggestion that a human was born to a virgin or that the individual had divine heritage was not uncommon in the ancient world. The following are some of the individuals who were claimed to have been fathered by a deity: Perseus (fathered by Zeus), Oenopion (fathered by Dionysus), and Romulus and Remus (fathered by Mars).
This is another scenario in which there may not be one specific belief, myth, or story that became the virgin birth story of Jesus, but the archetype of virgin/divine births was widespread and then incorporated into Christianity.