Have never read the book. However wasn't there a notation in the preface of the book that said it was fiction?
In these things I think everyone is wrong and everyone is right. No matter where you look they (religions, scholars, etc) all have a piece of the grand puzzle. Not the final answer or the complete puzzle. I think each group has a piece they are supposed to guard with everything they have. Catholics nail the Crucifixion (no pun intended) hard and keep it in everything they do, The Baptists believe in small community (started in the times of the Roman Empire), The Jewish believe God is one and the Christ was a prophetic speaker and not the son of God, and the list goes on. This list of puzzle piece holders is not limited to living religion followers, it does encompass even Pagan beliefs.
When will they figure out that they are supposed to come together and put the puzzle together once and for all? It's like a kindergarten room where we have given one piece to each kid, hop them up on sugar and leave them to figure it out.
![Grin ;D](http://forums.sohc4.net/Smileys/default/grin.gif)
While I know a lot on this subject but wont go where I do not know.
For reference Davinci was a man of science, he thought religion was used to fill in spots of ignorance.