The koran was not handed down by "allah" (A rock) directly to man. Every bit of it is aledged to have come out of Mohammads mouth, via a "angel" who beat him up and scared the crap out of him at first, then after he had mental fits and afterwards "recited" the Koran (and it was always about something to get Mohammad out of a jam). NONE of it was written down at the time. Nor was Arabic even a written language during Mohammads life. It was said that Omar collected all the Koranic sayings which were remembered by followers oraly and then written down long after Mohammads death, but there is not even evidence of that.
The first and only record of Mohammads life and saying was first written by Ishaq 180 years after Mohammad was dead. It's most probable that the first Koran was written from this work, which was then edited by Hisham and Tabari,Who edited some nasty crap out (and they admit it). This is the first and ONLY record of Mohammads life and sayings.
It was further edited and revised by Bukhari and his student,Muslim centuries later.
BTW, Nathan, I think there's sufficient evidence now to demonstrate that Mohammad, as he is portrayed in the Koran and the Hadiths, never really existed.