No one is going to produce proof that Jesus Christ did not rise from the grave three days after the Crucifixion, of course. Humankind will choose to believe or not that God revealed Himself in this fashion. But Islam stands at risk of a Da Vinci Code effect, for in Islam, God’s self-revelation took the form not of the Exodus, nor the revelation at Mount Sinai, nor the Resurrection, but rather a book, namely the Koran. The Encyclopaedia of Islam (1982) observes, "The closest analogue in Christian belief to the role of the Koran in Muslim belief is not the Bible, but Christ." The Koran alone is the revelatory event in Islam.
What if scholars can prove beyond reasonable doubt that the Koran was not dictated by the Archangel Gabriel to the Prophet Mohammad during the 7th century, but rather was redacted by later writers drawing on a variety of extant Christian and Jewish sources? That would be the precise equivalent of proving that the Jesus Christ of the Gospels really was a composite of several individuals, some of whom lived a century or two apart.
It has long been known that variant copies of the Koran exist, including some found in 1972 in a paper grave at Sa’na in Yemen, the subject of a cover story in the January 1999 Atlantic Monthly. Before the Yemeni authorities shut the door to Western scholars, two German academics, Gerhard R Puin and H C Graf von Bothmer, made 35,000 microfilm copies, which remain at the University of the Saarland. Many scholars believe that the German archive, which includes photocopies of manuscripts as old as 700 AD, will provide more evidence of variation in the Koran.