The date of composition is not fixed. The poem presupposes Babylon's political importance and Marduk's elevation, which points to the second millennium BCE, and proposals cluster in the range from the reign of Hammurabi in the eighteenth century BCE to the later second millennium, with many scholars favouring a date around the twelfth century under Nebuchadnezzar I, whose reign saw a marked promotion of Marduk. The evidence is indirect on all sides: the oldest manuscripts are centuries younger than any of these dates, the language is a literary register that resists close dating, and there is no external reference that pins it down. The range should be given as a range.
The strongest evidence for what the poem is doing comes from a variant. Assyrian copies from Ashur substitute Assur, the god of the Assyrian capital, for Marduk, with the accompanying genealogy and geography adjusted to fit. The same poem, structurally unchanged, promotes whichever city has the power to commission a copy. Few ancient texts offer so clean a demonstration that a theogony can be an instrument of state; the Assyrian scribes evidently understood exactly what they were editing.
The bulk of the surviving material comes from the library of Ashurbanipal at Nineveh, excavated from 1849 onward, supplemented by finds at Ashur, Kish, Sultantepe and Uruk. The text is well preserved by Mesopotamian standards but not complete, and the reconstruction rests on collating many partial copies from different sites and centuries rather than on any single manuscript.