It is of course heresy to say God didn't always exist. But there are dozens of scripture that says Jesus was around before creation. In fact Jesus Himself created creation. The same Jesus that was in the beginning is the person that dwelt among men.
The body God provided for his Son was "unto us a child is born", (Isa 9:6) Even Jesus said...."..... but a body have you prepared for me;..." (Heb 10:5) The child born was the body prepared for a Son who was given.
Jesus the "man" grew in wisdom, and stature.
Luke 2:40 And the child grew and became strong, filled with wisdom. And the favor of God was upon him.
The man Jesus did not know everything, but within his divine nature he knew all things. The fleshly mind, and the spiritual mind are two different things.
Interesting thought and first question. I'm sure you have already thought this out and have a perspective that you'll eventually share.
Are you seeing that all flesh initially is a clean slate waiting for it to be imprinted but in the case of Jesus was done so specifically by The Word of God, which allows for both Son of God and Son of Man? After contemplating the initial thought I added the latter part in my attempt of surmising where the question must direct one who believes in the Second Person of the Godhead and His manifestation in the flesh.
Once again be welcome to Talk Jesus Brother/Sister (?).
P.S. Love that Tract! I find it every once in a while traveling and having to make a rest room stop
I'll jump in with the notion that the earliest Jewish mindset didn't consider the "after life". Once they began considering the concept, it's apparent the Holy Spirit began updating the human mind as was practical for mankind to move forward and still be tuned into God's will and purposes. I suspect what mankind already realizes is less than 1% of what God has for us to comprehend.
I'll stop right there, as proceeding further will require delving into ancient cultural thoughts, and biblical revelations to those people degree by degree. Jesus completed the revelation aimed at His generation. That leaves room for either speculation or additional reliance on more revelations from Him as we humans need it. Grace is supplied according to sin realized. I don't know who started that thought enough to preach it, besides some hints from Paul.