The Greeks were known for writing stories about their family to make their family seam more important then they really were. Could it be the Jews started doing much the same after the Greeks took over? This would explain how several of the biblical stories seam Greek. Some of the other stories were just retellings of older Syrian, Assyrian, Egyptian and Babylonian stories that could have been changed at anytime like the story of Job a retelling of the poem of the righteous sufferer.
I think the Old Testament is much like the New Testament, Jesus was a retelling of a rising and dying savior but not a true copy cat story. In fact the story takes elements of several different stories and changes are made over the first 300 plus years to finally get what we have today. The Bible itself went over an evolution of changes to finally get what we have today .
I think it's going to be impossible for anyone to really get the bottom of how it all came to be.