The mainstream Christian view is that Jesus was born as the son of God. But this view wasn’t always the mainstream view amongst Christians. There are several other views, one of them is called “Adoptionism”.
“We know of a number of Christian groups from the second and third centuries that had an “adoptionistic” view of Christ. This view is called adoptionistic because its adherents maintained that Jesus was not divine but a full flesh and blood human being whom God had “adopted” to be his son, usually at his baptism.” – Bart Ehrman – Misquoting Jesus (p.155)
We know of a Jewish-Christian group called the “Ebionites”. They insisted that in order to be a follower of Jesus, one had to be a Jew. So the men were circumcised. It also meant that they had to follow the law given by Moses. Another big difference between the Ebionites and other Christian sects is that the were strict monotheists, believing only one could be God. So they didn’t see Jesus as divine, but as a human being no different from the rest of us. Jesus, according to the Ebionites, was born from the sexual union of his parents, Joseph and Mary. So there was no virgin birth according to them. What made Jesus different from all the others in their eyes, was that he was more righteous in following the Jewish law and because of his righteousness, God adopted him to be his son at his baptism, when a voice came down from heaven announcing that he was now God’s son.
Evidence in the manuscripts
People who upheld an adoptionistic view of Jesus, found evidence for this view in the Gospels. A lot of this evidence has been changed over time by scribes who had an anti-adoptionistic (believing Jesus was born divine) view. An example of this change can be found in Luke 3:22. Nowadays the text reads something like this:
“and the Holy Spirit descended on him in bodily form like a dove. And a voice came from heaven: “You are my Son, whom I love; with you I am well pleased.”
Here’s what Bart Ehrman says about it:
“In one early Greek manuscript and several Latin ones, however, the voice says something strikingly different: “You are my Son, today I have begotten you”. Today I have begotten you! Doesn’t that suggest that this day of baptism is the day on which Jesus has become the Son of God?” – Bart Ehrman – Misquoting Jesus (p.159)
So now we have two textual variants concerning this verse and which is the original?
Bart Ehrman goes on:
“The vast majority of Greek manuscripts have the first reading (“You are my beloved Son in whom I aim well pleased”) and so one might be tempted to see the other reading as the alteration. The problem in this case is that the verse was quoted a lot by early church fathers in the period before most of our manuscripts were produced. It is quoted in the second and third centuries everywhere from Rome, to Alexandria, to North Africa, to Palestine, to Gaul, to Spain. And in almost every instance, it is the other form of the text that is quoted (“Today I have begotten you”).” – Bart Ehrman – Misquoting Jesus (p.159)
Bart Ehrman concludes:
“These arguments suggest that the less-attested reading (“Today I have begotten you”) is indeed the original, and that it came to be changed by scribes who feared its adoptionistic overtones” – Bart Ehrman – Misquoting Jesus (p.159)
The view that Jesus was a divine being and/or the son of God from the get go, wasn’t always the mainstream view amongst all Christians. There were different views and one happened to became the mainstream view. There were different stories about this Jesus figure going ‘round at the time. Different Christian sects having different views. All based upon oral traditions. It’s amazing that Christians don’t know this or refuse to know this.