I would like to say that yes they overlap and come from many sources and are melded together. You may read one reference that says the myth originates over here and then another source that says it originates over there. These stories are ancient and I doubt you will get to the bottom of any origination. Except that they exist, except that they are shared and except that they are inspired or borrowed from one another. I have seen people get mad about it. Don't be mad, what is there to be mad about? If the origination of stories/myths of religions are of interest of you, then yes research and become as informed as you can. You won't be the first or the last to make a stab at it and you definitely won't be the final authority.
Another thing I would like to mention is that similar myths can exist without them being borrowed. They can exist on their own, because a thing can happen more than once that is similar to another thing as well as a person can think of a similar idea and express it although it has already been expressed somewhere else. This should not take away from its happenstance, nor the idea of the thing.
If you believe in the possibility of a spiritual life as expressed through unseen forces, you should consider that this unseen force, or these unseen forces happen across the board and have a multiplex of ways of expressing themselves. Do not be so conserned with the origination of a text or "right and wrong" when dealing with unseen entities, but live in love and experience the spiritual life for yourself. If you are hung up on history, confused, distraught, mad and angry about the origination of what is possible I think its time for you to move on. Consider the stories and contemplate their meanings, listen to your heart and live a life of love. It'll be easier that way. It is not about having it all figured out, or about YOU as an individual having all the answers about exact origination of a story. You yourself are a story.
I have found that even through questions you gain understanding.
Edited by SpiritWriter, 01 December 2013 - 10:54 PM.