And how did he turn fish into wine?

http://www.huffingtonpost.com/david-lose/where-did-the-bible-come-_b_893765.html

should give that a read

Ok just read it. From what I can gather we don't know?

There are various myths and conspiracy theories, so how do we know of its authenticity?

like many other things in religion you just kinda gotta take it with faith.
the bible is more of a guild line to instill morals to people than something that should be considered 100% stone wall truth.
a good example of other books that can teach us much about right and wrongs and morals is terry goodkind book 6 from the sword of truth series.
with it's not fact it can teach lesson's like bettering one own life instead of waiting for someone to do it for you while still bringing us entertainment.

thats just how i think of it anyway.

lol its water to wine. but yea, the article is correct