I am not aware of a religion that claims its writings go back to "the beginning."
If you are referring to the Book of Genesis, there is no claim that the book was written "in the beginning" nor is there any reason to think that the writer is trying to be clinically accurate or complete in the modern sense.
Genesis is obviously intended to be allegorical, but the detail it gives, and the literary style used shows the profound insight and genius of its author. Today, both religious and non-religious people miss the brilliance of the work because they are looking for the wrong things--often arguing about things that just aren't there.
In asmuch as Genesis tells the story of mankind's deliberate rebellion against Yahweh, it can certainly be said that human nature [as we know it] is accurately portrayed. It doesn't matter if you believe what the author is saying, but from the author's point of view the story is one of such enormous scope that the details are unimportant.
The story is a tragedy on a cosmic scale: in that sense, I would have to say that since all subsequent history attests to this, it is completely accurate.