Modern Christianity asserts an eternal Jesus, existing through all time as part of the trinity, however, groups of very early Christians believed Jesus was adopted by God, originally around the time of his crucifixion/resurrection or ascension, and later at his baptism. The Gospel of Mark indicates that its author subscribed to the latter view.
The Adoption AccountFrom the first chapter:
Mark 1:9 In those days Jesus came from Nazareth of Galilee and was baptized by John in the Jordan. 10 And when he came up out of the water, immediately he saw the heavens being torn open and the Spirit descending on him like a dove. 11 And a voice came from heaven, “You are my beloved Son;[d] with you I am well pleased.”
Bear in mind that Mark explicitly states that the beginning of the good news about Jesus Christ was John the Baptist preparing the way, quickly followed by the baptism of Jesus. The good news did not begin with Jesus' birth, according to Mark.
1 The beginning of the gospel of Jesus Christ, the Son of God.[a]
2 As it is written in Isaiah the prophet,[b]
“Behold, I send my messenger before your face,
who will prepare your way,
3 the voice of one crying in the wilderness:
‘Prepare[c] the way of the Lord,
make his paths straight,’”
4 John appeared, baptizing in the wilderness and proclaiming a baptism of repentance for the forgiveness of sins.
Furthermore, why would God incarnate even need to be baptised? The Gospel of Matthew gives an answer to that thorny problem. Because the author believed that Jesus was divine from birth, he needed to explain it. For Mark, however, no explanation was necessary; Jesus was just a man getting baptised until the dove descended.
Precedents in the Old TestamentThis was not a one-off! The Ancient Hebrews believed all their kings were adopted by God as his sons (everyone had divine kings back then). This is made clear here:
2 Samuel 7:12 When your days are fulfilled and you lie down with your fathers, I will raise up your offspring after you, who shall come from your body, and I will establish his kingdom. 13 He shall build a house for my name, and I will establish the throne of his kingdom forever. 14 I will be to him a father, and he shall be to me a son. When he commits iniquity, I will discipline him with the rod of men, with the stripes of the sons of men, 15 but my steadfast love will not depart from him, as I took it from Saul, whom I put away from before you. 16 And your house and your kingdom shall be made sure forever before me.[c] Your throne shall be established forever.’”
Look at Psalm 2:
2 The kings of the earth set themselves,
and the rulers take counsel together,
against the Lord and against his Anointed, saying,
7 I will tell of the decree:
The Lord said to me, “You are my Son;
today I have begotten you.
Mark 1:11 And a voice came from heaven, “You are my beloved Son;[d] with you I am well pleased.”
God's Anointed, the messiah, is the King of The Jews, a man adopted by God as his son.
This parallel was noted by Paul, by the way, as recorded in Acts 13:33.
Acts 13:33 God hath fulfilled the same unto us their children, in that he hath raised up Jesus again; as it is also written in the second psalm, Thou art my Son, this day have I begotten thee.
How Jesus' Family ReactedThe fact that Mark says his family thought him mad indicates no miraculous birth, or indeed anything miraculous at all until his baptism.
Mark 3:21 When his family heard about this, they went to take charge of him, for they said, "He is out of his mind."
It only makes sense when we realise that, in Mark's gospel at least, Jesus become the Son of God at the start of his ministry, and his family had no hint of his divine destiny until then.
Other VersesSome other verses of note:
Mark 2:10 But that you may know that the Son of Man has authority on earth to forgive sins”—he said to the paralytic—
The connection between these two verses is the word ὥστε, indicating that the second verse is a consequence of the first. But the first verse is talking about a man not a god, and so that only makes sense if Jesus is human, rather than God Incarnate.Mark 2:27 And he said to them, “The Sabbath was made for man, not man for the Sabbath. 28 So the Son of Man is lord even of the Sabbath.”
But Jesus Says "I have come..."Some apologists point to verses in Mark where Jesus says "I have come...". They argue they only makes sense if Jesus has come from somewhere, specifically from heaven. However, this is the standard phraseology of the prophets. See here for example:
Isaiah 61:1The Spirit of the Lord God is upon me,
because the Lord has anointed me
to bring good news to the poor;[a]
he has sent me to bind up the brokenhearted,
to proclaim liberty to the captives,
and the opening of the prison to those who are bound;
Jeremiah 14:14 And the Lord said to me: “The prophets are prophesying lies in my name. I did not send them, nor did I command them or speak to them. They are prophesying to you a lying vision, worthless divination, and the deceit of their own minds.
Differences in Early ManuscriptsIt is pretty well established that the ending of Mark was a later addition, but there is evidence of other tampering. Some early manuscripts omit "the Son of God" from Mark 1:1:
Mark 1:1 The beginning of the good news about Jesus the Messiah, the Son of God,
This could be a copying error, but it could reflect the fact that Mark did not believe Jesus was the son of God at that time, as this was before the adoption. Several early church fathers (eg Origen) quote Mark 1:1 without the "son of God" phrase (though Irenaeus quotes it with).