The opening of Mark is the closest thing to how Marcion apparently described Jesus coming into the world.
2 As it is written in the prophet Isaiah,
“See, I am sending my messenger ahead of you,
who will prepare your way,
3 the voice of one crying out in the wilderness:
‘Prepare the way of the Lord;
make his paths straight,’ ”
4 so John the baptizer appeared in the wilderness, proclaiming a baptism of repentance for the forgiveness of sins. 5 And the whole Judean region and all the people of Jerusalem were going out to him and were baptized by him in the River Jordan, confessing their sins. 6 Now John was clothed with camel’s hair, with a leather belt around his waist, and he ate locusts and wild honey. 7 He proclaimed, “The one who is more powerful than I is coming after me; I am not worthy to stoop down and untie the strap of his sandals. 8 I have baptized you with water, but he will baptize you with the Holy Spirit.”
9 In those days Jesus came from Nazareth of Galilee and was baptized by John in the Jordan. 10 And just as he was coming up out of the water, he saw the heavens torn apart and the Spirit descending like a dove upon him. 11 And a voice came from the heavens, “You are my Son, the Beloved; with you I am well pleased.”
12 And the Spirit immediately drove him out into the wilderness. 13 He was in the wilderness forty days, tested by Satan, and he was with the wild beasts, and the angels waited on him.
14 Now after John was arrested, Jesus came to Galilee proclaiming the good news of God 15 and saying, “The time is fulfilled, and the kingdom of God has come near; repent, and believe in the good news.”
In this form the work does state that Jesus existed as a person first who came from Galilee. But it is so close to saying something else, in fact closer than any other known Gospel.
It is odd that this narrative begins with Jesus coming out of from nowhere "from Nazareth".
If v9 is removed, we can imagine that it was John who saw the heavens torn apart, not Jesus. And what John saw was the Spirit of Jesus descending from heaven. The way we read this now it is a form of adoptionism in which Jesus sees the Holy Spirit descending onto himself, but so much of this would seem to support the view that this is a revision of a narrative that actually began with John seeing the heavens torn apart and seeing Jesus descend from the heavens.
V12-14 has never sit well with me. Its is very clunky, but has always been chalked up to "Mark's style". Something is odd here. V4 says that Joh appeared in the wilderness and that he was baptizing in the wilderness. Jesus, then, is apparently baptized in the wilderness. But v12 says that "he" is driven into the wilderness. But isn't he already in the wilderness?
Then in v14 we are simply told that John was arrested, but there is no context at all. Again this is chalked up to Mark's "quirky style". Then we are told that Jesus "came to Galilee". But we were just told that Jesus came from Galilee. V14 acts as if Jesus is coming to Galilee for the first time. It doesn't say that he returned.
It makes me wonder, if originally the narrative was that John was in the wilderness baptizing and John saw Jesus descend from heaven and John was the one who was tested by Satan and then arrested. And it was after John was arrested that Jesus showed himself in Galilee. Think about this in the context of the opening of the Gospel of John.
6 There was a man sent from God whose name was John. 7 He came as a witness to testify to the light, so that all might believe through him. 8 He himself was not the light, but he came to testify to the light. 9 The true light, which enlightens everyone, was coming into the world.
10 He was in the world, and the world came into being through him, yet the world did not know him. 11 He came to what was his own, and his own people did not accept him. 12 But to all who received him, who believed in his name, he gave power to become children of God, 13 who were born, not of blood or of the will of the flesh or of the will of man, but of God.
14 And the Word became flesh and lived among us, and we have seen his glory, the glory as of a father’s only son, full of grace and truth. 15 (John testified to him and cried out, “This was he of whom I said, ‘He who comes after me ranks ahead of me because he was before me.’ ”) 16 From his fullness we have all received, grace upon grace. 17 The law indeed was given through Moses; grace and truth came through Jesus Christ. 18 No one has ever seen God. It is the only Son, himself God, who is close to the Father’s heart, who has made him known.
19 This is the testimony given by John when the Jews sent priests and Levites from Jerusalem to ask him, “Who are you?”
In the context of John, we can imagine that John is testifying to seeing Jesus enter the world from heaven. And if so, is that not really what happened in the opening of Mark?
Maybe this is all nothing, and I'm just barking at shadows, but this looks suspiciously to me like a narrative that has been revised. I also still find it hard to believe that Marcion's Gospel looked more like Luke than Mark. There are so many aspects of Mark that fit Marcion's apparent theology better than Luke. It makes me wonder if there was really some other version of the Gospel that was a cross between Mark and Luke (keeping in mind that Luke is already very similar to Mark).