Let me notify, I'm a literal devotee of Dan Brown books. Although, his books are mainly brain thrillers-- do they actually fill up our minds with genuine facts? I have believed most of his statements blindly, but I do not really believe that the Priory of Sion was established in the 1200 AD. Through a lot of research and references, I have inferred that the secret institute was actually formed in the 1950's.
But Mr. Leo had that one society in his mind to continue female worship. So it was only restricted to that thought because the real society was actually established somewhere during 1950s. I believe almost anything which Mr. Brown states, but not everything.
You do know that this book is fiction, a story, not to be read like it is the truth, a fairy tale I cannot see how anyone would take any piece of this book as real or fact. It does not even warrent 50 words for a min. Word count.
When a book is sold as "Fiction", it is fiction. Duh! That's a no-brainer. Brown's novel is part of the Fiction genre. It isn't even the first piece of fiction to entertain the idea that Jesus Christ left a bloodline with Mary Magdalene. BUT ... There has NEVER been any historical, biblical, apocryphal, archaeological, genealogical, or genetic evidence that supports this hypothesis. Therefore, it makes it impossible to call anything about "The Da Vinci Code" (or the other literary works on the subject) fact. Is it interesting? Yes. Does it make you ponder the idea? Sure. Still, it remains a work of fiction based on hypotheticals.
Dan Brown's works are FICTION. Poorly written fiction at that, with one dimensional characters, overuse of exposition, and predictable plot lines. It's not even original- he got sued because a large portion of "The DaVinci Code" was taken from another book. For crying out loud, the man doesn't even know "DaVinci" wasn't the Master's name, but the place he was born.
His books are conspiracy theory craziness, not actual history or archaeology. It's actually rather terrifying to me that so many of his readers think his books are based on historical information.