In the same way that Jesus would have been Jewish, what would have been the prevailing religion in Mecca/Medina during the 7th century? Who ruled over that area at the time?
Not to hijack the thread, but I'd like to see if anybody knows this and it seems to be somewhat related to the topic question. I've often heard that Muhammad had a Christian uncle. Is there any truth to this?
Are you interested in knowing specifically what Muhammed's personal religious affiliation was before the revelation, or are you more looking for an understanding of the religion of that area at the time?
Meccans were generally polytheists and worshipped idols. We know of several of these deities. For example, Al-Uzza was the goddess of fertility and war (one of Mohammad's paternal uncles was named Abduluzza which means the servant of Uzza), Al-Lat was the goddess of underworld and Al-Manat was the goddess of fate. These three are mentioned in Quran (Najm, 19-20).
The chief god of Quraysh (Mohammad's tribe) was considered to be Hubal.
Mohammad's clan was nobility and custodians of Kaaba which housed as many as 360 idols in it and a considerable part of their wealth and prestige came from the worshippers and pilgrim who visited Mecca. Although we don't know much about Mohammad's life before Islam, It is safe to assume that he himself worshipped these deities in his youth.
For more information about the deities worshipped before Islam, you should read [Book of Idols] (http://answering-islam.org/Books/Al-Kalbi/).
Hello! As a starting point, you can look at the FAQ, there have been some questions related to yours that have been answered to there.
Edit: Apparently the FAQ is not as accurate as I thought on this subject, see /u/shlin28's answer below