Not to be argumentative, Jim, but there is very good evidence that Genesis was NOT oral, but written from the beginning. In Genesis 5:1 we have evidence of that internally. In addition, archaeologists have found that the earliest Middle Eastern tablets we have found bear the authors name and 'title' of the document at the END, not at the beginning of the document. We see this very thing eleven or twelve times in Genesis. There is thus evidence both internally and externally that Genesis is a series of eyewitness accounts, written down, and passed down. Moses inserted some editorial comments, which are fairly easy to pick out, and, as editor, the book is "his". From him came the first five books and they are credited to him, but the first book is his as editor only. There is too much detail, too many exact conversations, and the various authors' sign-off signatures for it to be otherwise.
However it should also be stated that oral tradition, before the RC church started using it as an excuse for changing doctrines and heresies, was something which was handed down from TRAINED person to TRAINED person. The second person would be trained by the first to repeat the information EXACTLY, and not to add or subtract anything from it. This was common in other cultures, but the Hebrews had written manuscripts and did not have to depend on this method of transmission.
So, in essence, the very fact that the RC church says it is rooted in tradition as well as Scripture is a sort of 'hidden' admission that they have pagan roots and carry them on.