Adam is also the first sinner. (Hosea 6:7, Romans 5:12-14; 1 Cor 15:22) He bears the guilt for the human race opposing God. We are God’s enemies because of his sin. Why? Because we were all “in” him when he rebelled. He is the source of us all. In him is the start of all of our lives. When he defied God, we all defied God.
Except for two.
There are only two humans who were not “in” Adam when he rebelled. One had already been taken out of him, so that she could provide Adam’s humanity (before sin) for the One who was “out-sourced.”