You are using an out of date browser. It may not display this or other websites correctly. You should upgrade or use an alternative browser.
alternatehistory.com
There was these last few days [post=12246455]an active thread[/post] where the subject of the Early history of Islam came to be discussed.
In order to simplify the question, let us say that there are 3 different options (plus an escape clause):
The traditional Muslim account is basically correct. There was a prophet called Muahmamd who preached a new religion in Mecca in the early VIIth century. The Quran is a collection of his sermons (more or less redacted later on). The Muslim community was led after his death by a series of 4 Caliphs (Abu Bakr, Umar, Uthman and Ali), then by the Umayyad dynasty who usurped the Caliphate from Ali, then by the Abbassids who overthrew the Umayyads in the 750s AD. All caliphs were descendant of close relatives of Muhammad within his clan, the Quraysh.
The traditionnal Muslim account is an Abbassid fabrication. There was no prophet Muhammad and Mecca did not exist before it was declared to be the destination of the Hajj in Abbassid times. The Arab conquest in the early VIIth century took place as a result of local initiatives by Arab chiefs who were former Roman or Persian vassals ("quraish" i.e. "foederati" in Syriac-Arabic dialect). The Arab conquered areas were federated in the 660s AD by Muawiya, who founded the Umayyad dynasty. This dynasty was overthrown in the 750s AD by a coalition formed between several south Mesopotamian Arab clans and a sectarian Perso-Arabian religious movement initiated in Khurasan by a preacher known as "Abu Muslim". This preacher galvanized his supporters by telling them the story of a prophet Muhammad who had founded the religion of the Arabs and authored the Quran (actually a collection of Arabic-Syrian monotheistic tracts of various origins, widely circulated in the Umayyad sphere of influence). After the successful overthrow of the Umayyads, the Mesopotamian Arab clan that came out on top, the Abbassids, had an official version of the Muhammad myth written to justify their rule. In traditional tribal fashion, this myth gave kin ties with the Prophet's clan (called the "Quraysh" in order to re-use as many real elements as possible) to every of the important protagonists of the story.
The traditional muslim account is quite distorted but at least Muhammad, the Quran and Mecca actually existed.
What really happened is completely different (escape clause!)
Whatever you think is closer to the truth, please care to elaborate.