So it seems that Genesis, which is this story, developed from oral traditions about Moses.
In order to understand the reason for the creation myth, one has to understand the mind set of the exiled Jews in Babylon and also understand the Babylonian and Persian myths that influenced them. Because of their need to elevate their god as well as the importance of their relationship to their god, the Jews had to formulate a majestic myth that outdid the myths of their captors. Before creating those myths the Jews had both a documented profane history and sacred history, but they merged them in order to make the profane appear to have supernatural origins so to convince the world that they were the chosen people, and for the most part, it worked. They even convinced themselves eventually.
It's also important to understand how vital lineage was to this culture. One's lineage determined one's standing in society and carried with it certain rights. Without lineage, one had little or no rights. One's identity was entirely determined by the father and backwards in a irrefutable familial tie with the past which determined land and property ownership, marriage, and one's role in society. The ability to hold office, including the priesthood and kingship, was entirely determined by such heritage. Women had no rights of their own, always being considered to be the property of a man. Jewish households maintained strict genealogical records and leading families actually stored these documents in a public archive in the temple mount. When the Jews returned to Jerusalem from exile, it was even more important to be able to prove lineage in order to reestablish the structure of society and reclaim property as well as prove their racial purity. (Remember the insanity over "mixed marriages")
We can see that even into the writing of the New Testament, lineage was still a major issue witnessed by the enormous effort put into establishing Jesus' lineage. Today we believe in inalienable rights given by our Creator, but in the culture of that time there was no such thing; rights were given by birth through the human father, not the divine Father. That is one of the reasons why Jesus' message of spiritual sonship with the Father was such a powerful message in first century Palestine.
So, you can understand the preoccupation those exiled scribes had with tracing the Jewish race back to the first man. But, they had difficulty when they came to Abraham and decided to wipe out the human race with a flood and claim that Abraham was a descendant of Noah and Noah was a descendant of Adam. The reason they picked the flood story is because of the myth of Gilgamesh
and an earlier Sumerian story, Eridu Genesis
, both of which they used as prototypes for their own Genesis story.
78.7.3 Almost five thousand years later, as the Hebrew priests in Babylonian captivity sought to trace the Jewish people back to Adam, they found great difficulty in piecing the story together; and it occurred to one of them to abandon the effort, to let the whole world drown in its wickedness at the time of Noah’s flood, and thus to be in a better position to trace Abraham right back to one of the three surviving sons of Noah.
78.7.4 The traditions of a time when water covered the whole of the earth’s surface are universal. Many races harbor the story of a world-wide flood some time during past ages. The Biblical story of Noah, the ark, and the flood is an invention of the Hebrew priesthood during the Babylonian captivity.
You will note that there are at least ten principal genealogical lists in Genesis alone. This was the Hebrew attempt to legitimize their sonship with the first man God created, and thus establish their connection with Deity. It was the Babylonian captivity that inspired the scribes to connect the Jewish race back to Yahweh, because the Babylonian myths had already established that they were descended directly from the gods. The Jews had to establish that they were descendants from the one true God in order to legitimize their chosen people status. Because they mistakenly believed that Adam was the first man created by God, due to their earlier creation stories dating from the time of Moses, they desperately needed to establish that link with him in order to prove that they were directly descended from Yahweh.
74:8.6 The Babylonians, because of immediate contact with the remnants of the civilization of the Adamites, enlarged and embellished the story of man's creation; they taught that he had descended directly from the gods. They held to an aristocratic origin for the race which was incompatible with even the doctrine of creation out of clay.
74:8.7 The Old Testament account of creation dates from long after the time of Moses; he never taught the Hebrews such a distorted story. But he did present a simple and condensed narrative of creation to the Israelite, hoping thereby to augment his appeal to worship the Creator, the Universal Father, whom he called the Lord God of Israel.
74:8.8 In his early teachings, Moses very wisely did not attempt to go back of Adam's time, and since Moses was the supreme teacher of the Hebrews, the stories of Adam became intimately associated with those of creation. That the earlier traditions recognized pre-Adamic civilization is clearly shown by the fact that later editors, intending to eradicate all reference to human affairs before Adam's time, neglected to remove the telltale reference to Cain's emigration to the "land of Nod," where he took himself a wife.
74:8.9 The Hebrews had no written language in general usage for a long time after they reached Palestine. They learned the use of an alphabet from the neighboring Philistines, who were political refugees from the higher civilization of Crete. The Hebrews did little writing until about 900 B.C., and having no written language until such a late date, they had several different stories of creation in circulation, but after the Babylonian captivity they inclined more toward accepting a modified Mesopotamian version.
74:8.10 Jewish tradition became crystallized about Moses, and because he endeavored to trace the lineage of Abraham back to Adam, the Jews assumed that Adam was the first of all mankind. Yahweh was the creator, and since Adam was supposed to be the first man, he must have made the world just prior to making Adam. And then the tradition of Adam's six days got woven into the story, with the result that almost a thousand years after Moses' sojourn on earth the tradition of creation in six days was written out and subsequently credited to him.
So, you can see that the story of Genesis is derived from much more than the oral traditions about Moses.