The Gilgamesh epic (circa 2,000BCE) predates the two Genesis accounts of creation and a great flood. The anonymous writers of Genesis I and Genesis II borrowed the Assyrian flood myths, possibly during the Captivity in Babylon. Whereas the original flood myth has the ark landing upon Mount Nisir (Gilgamesh Epic Tablet 11), the later Genesis flood myth has the ark landing on Mount Ararat (GEN 8:4).
The Yahweist version of Genesis (Genesis II) was written around 950BCE. The Elohist version (Genesis I) was written about 750BCE. The Account of "Noah's" flood (Genesis VII) was written around 440BCE. In all, it took roughly five hundred years and about six authors to write all of Genesis: and all of it post-dates the Gilgamesh Epic.
There is even an older version of the Gilgamesh flood (and therefore much older than the Genesis flood myth), where the figure of Ut-napishtim (and, later, Noah) was preceeded by the Sumerian Ziusudra. These pre-Genesis accounts (25,000 clay tablets) were recovered from the palace of the Assyrian king Ashurbanipal at Nineveh, in the mid 1800s. We find that the original "Adam" was a man named Adapa. The original account of creation which the authors of Genesis plagerized is known as the "Enuma Elish" (The start of the seven tablets that record the creation event, translated as "When on High...."). Anyone who believes that the two creation accounts in Genesis are unique and the first, therefore have no excuse for their ignorance. Rev Gish, Rev Morris, and the other preachers at the ICR cult therefore have no good excuse for spewing their lies about "Noah's flood."