Hi ChurchBoy!
One of the standard procedures in looking for an original telling of something vs. a later, possibly legendary, account, is to look for a lack of mythological elements. Just comparing Gilgamesh and the Bible, there is an abundance of mythological elements in Gilgamesh while they are totally lacking in Genesis.
What I have here is John Gardner and John Maier's translation of Gilgamesh. It is not my favorite, but it will do for this. I'll go through some of it for you and point out some things. Also, though, notice that there are some details which the Bible does not have which make it interesting. I'll start with Tablet XI, column 1:
Gilgamesh said to him, to Utnapishtim the remote one:
'Utnapishtim' is the name for Noah here. I have not been able to find any literal translation of this Akkadian language name. It is interesting, however, that he is referred to as 'the remote one.' If this is a true reference, then we have a clue about how the Flood and the aftermath of civilization affected Noah -- he withdrew from men.
"I look at you, Utnapishtim.
Your features are no different than mine. I'm like you.
And you are not different, or I from you.
Here, Utnapishtim is clearly identified as a human being.
Your heart burns entirely for war-making,
yet there you are, lying on your back.
Tell me, how did you stand in the Assembly of the Gods, asking for life?"
Here we have the first mythological element: this man stood in the assembly of the gods. However, there are some interesting points to note as well -- his heart burns for war-making? Is this also a reaction to the evil which erupted so quickly again after the Deluge? Or was this person known as a warrior before? In the Bible we read of Noah's character only that he was righteous (which means he believed that God would send a Redeemer) and that he obeyed God. We know nothing of him other than that from before the Flood. So, for me, this is one of the elements that is a tease. Was it added? Or is it simply a detail the Bible does not have?
He is also said to be 'lying on his back'. Was this from age, or is it symbolic, or is it idiomatic? We are not told, and any one of the answers can fit.
However, a human standing in the assembly of gods is an clearly recognizable mythological element. It is seen in a number of clearly defined myths -- think about those of the Greeks and Romans which most have some acquaintance with in our western cultures.
Utnapishtim says to him, to Gilgamesh:
"I will uncover for you, Gilgamesh, a hidden thing,
tell you a secret of the gods..."
And thus begins Utnapishtim's recital of a conference among the gods. This is also a clearly recognizable mythological element.
In stark contrast, we have, in the Bible, God -- one God -- approaching Noah with directions. Nothing is mentioned which Noah himself has not witnessed or heard, thus giving the effect of an eyewitness account to the biblical rendition of the story, again in contrast to the epic of Gilgamesh.
And yet, in the Gilgamesh epic, in lines 23-25, we have echoes of the Bible and an interesting note:
Tear down the house. Build an ark.
Abandon riches. Seek life.
Scorn possessions, hold onto life.
First of all, 'tear down the house' may be referring to an actual house, or it may be idiomatic as explained by the next two lines -- ignore and abandon what you have built up for yourself and seek life instead. This is repeated by Jesus Himself, in essence, in His advice to the rich young man in Matthew 19:16-29 and parallel verses in Mark and Luke.
The next two lines of Gilgamesh are very interesting:
Load the seed of every living thing into your ark,
the boat that you will build.
This may not be quite what it appears to be at first glance. "every living thing" may refer to those things with nephesh, or the breath of life, as referred to in Genesis 7:15. The reference to seed cannot be to the descendants of those he would take on the ark, for that is a logical impossibility. It must, then, refer to the fact that what he is to take onto the ark is the seed of 'living things' -- which may be a reference back to created kinds.
What we do see here, though, in wading through this, is a fuzziness that is not found in the Bible. The biblical account is extremely clear about just what is and is not to be taken aboard the Ark and how many of which. This is a clear and precise detail which we would look for in an original account but which is often lost in following legends.
We also have some direct contradiction, or at least apparent contradiction, in lines 80-95 in the Gilgamesh epic. At first we read that Gilgamesh loads all he has of silver and gold onto the Ark (thus disobeying the order to abandon riches and scorn possessions!), but at the end of column 1, we also read that "For the caulking of the boat I gave to Puzur-Amuru, the shipbuilder, my palace with all its goods."
One of the things that has fascinated me about looking for the memories within the legends is that amazing detail can be added. In the Bible, we are told only that the great fountains of the deep burst and that it rained for forty days and forty nights afterwards.
If we keep in mind that 'forty' may indeed be forty as well as symbolizing 'many', and if we keep in mind that 'seven' also symbolized completeness to the ancients, look at some of the detail in the Gilgamesh epic that may indeed be fleshing out a little of what the catastrophe was like. The following is from column 3:
When something of dawn appeared
a black cloud rose up from the horizon.
Adad the thunder god roared within it.
Nabu the god of despoilment and Sharru the god of submission rushed before it,
moving like heralds over mountains and land.
Nergal of the underworld breaks his doorposts.
Ninurta comes, making the dikes flow.
The Anunnaki lift up their torches:
the land glowed in their terrifying brightness.
The confusion of Adad sweeps the heavens
turning all that was light into blackness.
The wide land was smashed like a pot.
For one day the south wind blew:
it gathered speed, stormed, submerged the mountains.
Like a war it swept over everything:
brother could not see brother;
from heaven, the people could not be sighted.
The gods themselves were terrified by the Flood:
they shrank back, fled upward to the heavens of Anu.
Curled up like dogs, the gods lay outside [his door].
Ishtar cried out like a woman giving birth,
the sweet-voiced lady of the gods cried out,
"The days of old are turned to clay
since I spoke evil in the Assembly of the Gods.
...I myself gave birth to my people!
[Now] like the children of fish they will fill the sea!"
...Six days and seven nights the wind shrieked,
the stormflood rolled through the land.
On the seventh day of its coming the stormflood broke from the battle
which had labored like a woman giving birth.
The sea grew quiet, the storm was still; the Flood stopped.
I looked out at the day. Stillness had settled in.
All of humanity was turned to clay.
The ground [surface] was like a great, flat roof.
I opened the window and light fell on my face.
I crouched, sitting, and wept.
My tears flowed over my cheeks.
I looked for a shore at the boundary of the sea,
and the twelfth time I looked, an island emerged.
The ark stood grounded on the mountain Nisir.
The mountain Nisir seized the boat; it could not rise.
I have bolded the bits which interest me in terms of clues we might be able to take quite literally.
But it is also evident that the forces of nature are considered to be under control of the gods. This is considered mythological. However a thought comes to my mind here -- there are references in the Bible to angelic beings having some identity with or control over the forces of nature here on earth. Would these, then, have been worshiped as gods by those who abandon the faith in their Creator God? Just a thought in my mind...
At any rate, the Gilgamesh epic post-dates the Genesis account from internal as well as external evidences.
1. The Genesis account presents a first-person eyewitness account of what happened, signed off by Noah's sons in Genesis 10:1. The Gilgamesh account is the result of an interview Gilgamesh had with Noah much later.
2. The Genesis account contains no mythological elements. The Gilgamesh account does. Myth follows reality, it does not precede it.
I taught Gilgamesh before in several English classes and it was actually this epic which sparked by desire to research into the legends around the world and try to tease out the cores of truth in them. It is an ongoing project and one I enjoy very much. At any rate, linguistically, internally, and historically, the Genesis account definitely shows evidence of predating the Gilgamesh account. You will find that those who try to reverse that order are those who are trying to debunk the Bible in general and Genesis in particular.