The DaVinci Code deals with the four Gospels, the last of which was written by St. John around 100 AD. John was the youngest Apostle, and he was asked to put his recollections down to give a more personalized account. He referres to himself in the stories as "the disciple whom Jesus loved." Your perception may be based on the first historical referrences to the New Testament, which did not come about until centuries later (nobody of importance noticed Christians before then, so there were no remarks on them). However, the documents did exist, as archeological evidence has shown.