The Tower of Babel story in its present form probably dates to the Neo-Babylonian era when Nebuchadnezzer II restored the ancient ziggurat of Etemenanki and enlarged it into the most massive building of its kind ever built (tho smaller than the Great Pyramid of Khufu). His father Nabopolassar, in an inscription, relates how he was commanded by Marduk to "lay its foundations firm in the breast of the underworld, and make its top equal to heaven" (KIB, iii. 2.5) Compare this phrasing with Genesis 11:4 where the builders declared their intent to build "a tower with its top touching the heavens". This coincidence in wording suggests that the Hebrew story draws on Akkadian sources. The name Etemenanki in Sumerian also means "house of the foundations of heaven and earth," expressing again the idea of the tower as a bridge between earth and heaven. It formed part of the complex of Esagila (lit., "the house that rises its head") that was dedicated to Marduk. The legend of the Esagila's founding is told in the Babylonian primeval history epic, the Enuma Elish. Again we find wording very close to that in Genesis 11:
Enuma Elish VI 60-62: "Let its brickwork be fashioned...The Annunaki applied the implement; for one whole year they moulded bricks. When the second year arrived, they raised high the head of Esagila toward the heavens [Apsu]."
Genesis 11:3-4: "Let us make bricks and bake them in a fire....Let us build ourselves ... a tower with its top reaching heaven."
But here is the crucial thing....there is nothing in the Enuma Elish about a confusion of languages. This motif instead comes from a completely different tale in the Epic of Enmerkar (c. 2000 BC), which describes an idyllic time in ages past when:
Epic of Enmerkar: "There was no snake and when there was no scorpion, there was no fear, no terror....In those days the land of Martu, resting in security, the whole universe, the people in unison spoke in unison to Enlil in one tongue. Enki, the Lord of wisdom, ... changed the speech in their mouths, [brought] contention into it, into the speech of man that [until then] had been one."
Genesis 11:1, 9: "Now the whole world had one language and one speech .... Yahweh confused the language of the whole world."
Again, we find very similar wording in the more ancient Akkadian/Babylonian parallel. But this story about confusing the speech of man has nothing to do with the building of a tower. The Yahwist narrative in Genesis 11 appears to combine two separate Akkadian traditions into one story. Bible scholars working in source criticism had also independently detected two separate stories that had been combined together in Genesis 11, mostly because of the large number of doublets in the rather short passage. When the two stories are untangled (cf. Gunkel, Skinner, etc.), we can see that the motif of the confusion of language does not come from the "Tower" story but instead from the "City" story:
The City Recension (Gen. 11:1, 4a, b, 6a, b, 7, 8, 9)"And it happened the whole world had one language and one vocabulary. And they said, ?Come, let us build a city, lest we be scattered over the face of the earth.? And Yahweh said, ?See, they are one people and they have all one language. Come, we will go down and confuse their language there, so that no one understands the language of his neighbor!? And so Yahweh scattered them from there over the face of the whole earth, and they left off building the city. For this reason its name is called Babel, because there Yahweh confused (Heb. balal "confuse") the language of the whole world, and from there Yahweh scattered them over the whole earth."
The Tower Recension (Gen. 11:2, 4c, b, 3a, b, 5, 6a, c)
"And as they journeyed from the east, they found a plain in the land of Shinar and settled there. And they said to each other: ?Come, let us make a name for ourselves and build a tower with its summit touching the heavens. Let us make bricks and bake them thoroughly!? And so they used brick for stone and bitumen for mortar. Then Yahweh came down to look at the tower that the sons of men had built. And Yahweh said: ?This is only the beginning of what they will do. Henceforth nothing will be impossible for them in what they propose to do.? (recon.) And so Yahweh sent a wind against the tower and threw it to the ground. That is why the land is called Shinar because it was there the tower was overthrown (Heb. na'ar)."
The merits of Gunkel's analysis (which recalls how the P and J stories of the Flood were woven together) may be debated, but interestingly it dovetails the separate origin of the motifs in Akkadian sources. It is the Tower Story that shares features with the Inscription of Nabopolassar and the Enuma Elish. In this story the human motivation was pride and a desire to reach heaven (as proclaimed by the real-life builders of Esagila and Entemenanki) and the divine response was overthrowing the tower, a response that is a play on the name Shinar (Heb. na'ar "overthrow"). In the City Story, on the other hand, the human motivation was the desire to maintain unity and the divine response was confusing their language, a response that is a play on the name Babel (Heb. balal "confuse"). It is the City Story that shares parallels with the very different Babylonian legend about confusing the language of men to destroy their unity (Epic of Enmerkar). Because the most famous tower was in fact located at the city of Babylon and because of the formal similarity of the stories, the two accounts were combined together into a single narrative, omitting what would have been original ending to the Tower Story in the process (which is reconstructed in the analysis above).
We are fortunate, however, that the original ending may well have been preserved in other ancient Jewish writings. We therefore find in Jubilees 10:26: "And the Lord sent a wind against the tower and overthrew it to the ground. It is now between Asshur and Babylon in the land of Shinar. He named it the Collapse." The same story is told in Sibylline Oracles 3:101-107: "But immediately the Immortal One imposed a great compulsion on the winds. Then the winds cast down the great tower from on high, and stirred up strife for mortals among themselves." Sibylline Oracles 11:10-13 also reads: "The tongues were loosed, but on them came the wrath of the Most High God, hurled down, and the wondrous tower fell." Also in Jewish rabbinical literature, in Midrash Tanhuma, Noah 18, we read: "Said R. Hiyya bar Abba: Of the tower that they made, one third was burned, one third was swallowed up, and one third is still standing."
This is not to say that this is the only way to look at the evidence, but these are some of the findings by earlier literary critics on the subject. The main issue, I think, is whether the two stories were combined in a pre-literate oral stage or were drawn from actual literary sources (as assumed by Gunkel). It may well be that the composite narrative was formed in oral folklore, but on the other hand, if the story does draw on rather late Neo-Babylonian material, it could also represent a creative formation of a new story by the author of J or the redactor on traditional materials. There is too little evidence to decide either way....