Modern Islam incorporates figures, ideas, and content from Judaism and Christianity.
If Islam appears to be heavily spawned from these Abrahamic religions, it raises the question of how these religions spread to the Arabian peninsula in order for originators of Islamic doctrine to be so heavily exposed to them.
Were Christianity and Judaism well-known to at least some subset of the society?
Wikipedia says that the two major cities in the Arabian peninsula at the time (around 600 C.E.) were Mecca and Medina, and that the predominant religions in Mecca were polytheistic religions of Arabian tribes.
It seems to me like there must have been a really significant knowledge of Judaism and Christianity in order to develop a religion which arguably heavily revises, incorporates and extends them.
Is there any historical evidence or knowledge of the evolution of Islamic doctrine and how its chronology may coincide with the entrance of these religions into the Arabian sphere?
This manuscript of the Quran which may have been written while Mohammed was still alive (I think) has much of the core content of the modern Qu'ran.
Therefore, I feel like there has to be some strong link between a significant exposure to Christianity and Judaism and an offshoot religion developing from them. But what was it? Was it only foreign exposure for a few travellers, or had these religions already spread to Arabia? Also, it is said that Jesus was a reformed Jew who (maybe) had grown up amongst Jewish culture and religious teachings. Whereas it is not emphasised (as far as I have seen) that Muhammad was significantly taken by Christianity enough to want to adopt elements from it, that he was involved in it for a time. I read that he had exposure to it and that he spoke positively of it, but I would expect something much further, like, surely his (or others') first exposure to these religions must have been personally significant enough to want to appropriate and augment them (given how extensively Islamic theology is based completely on a foundation of Judaism and Christianity as real revelations, part of the master narrative of God's periodic emergence to select prophets.) Unless, as is possible, Mohammed / others were exposed to Christianity and were inspired to ideas of their own without ever having much interest in becoming Christians or ever practising it.
