If we were created in God’s image and somehow fallen man still maintains some of that image [see Js 3.9], then what part of the image of God was lost by our fleshly father Adam in the Garden? He wasn’t conceived by normal, fallen, human means and neither was Jesus. So, I think that what was lost in the Garden has something to do with humanity’s sonship to God.
In whatever way we fell in Adam, one thing is sure, Jesus is complete in that way. This is the backdrop to what Paul says in Rom 5.12-21. Perhaps this must also be in view to rightly understand Rom 8.29. Here, Paul says that all those whom God predestined, He did so for them to be conformed to the image of Jesus. He says this because it exalts Jesus’ Sonship and makes those who were not God’s sons into His sons by adoption [Rom 8.15, 23]!
So, I think Paul supports the fact that in the fall, man’s sonship with God was lost. James appears to be on board with this. He says that with the tongue “we bless our Lord and Father, and with it we curse men, who have been made in the likeness of God” [Js 3.9]. See the implication. Additionally, in losing sonship, somehow we also lost moral uprightness. I’ve yet to ponder how the two are connected. “When the fullness of time came, God sent forth His Son, born of a woman, born under the law, so that He might redeem those who were under the law, that we might receive the adoption as sons” [Gal 4.4-5].