The early record of Genesis is the locus of all manner of speculation, from young earth creationists to allegorical views that see the book as little more than one tribe’s attempt to explain the mysteries of the cosmos. Aside from how God has created all things seen and unseen is the question of whether the first man was an actual being, or whether he is simply a genus, a middle eastern explanation of humanity. The question, in short, is whether Adam is an historical figure. If there is no historical Adam, it alters much more than cosmology. The doctrine of soteriology is likewise affected. Apart from what is in Genesis itself, one has to consider other parts of Scripture as commentary.
Adam as federal head
The record of the fall includes Adam eating of the tree, but he does so after Eve presents him with the fruit. She had already eaten, but the race was not plunged into sin when she did so. Adam, as head, acts representatively when he sinned and thus we read “For as in Adam all die” (1 Cor 15:22) Because he was first created, Adam is in a position of headship—and of greater responsibility. Culture cannot alter this creation order. Adam as the head of the human race plunged his progeny into sin by his rebellion. In Romans Paul is equally clear as he is in 1 Corinthians. “Sin came into the world through one man, and death through sin.” (Rom 5:12) This presupposes an historical Adam, one man. Our experience of sin and its consequences is not metaphorical or allegorical, but actual. This, too, argues for an historical Adam.
Christ as federal head
Again in 1 Corinthians, Paul quotes from Genesis 2:7 when he says “Thus it is written, “The first man Adam became a living being”; the last Adam became a life-giving spirit. He makes the connection between Adam and Christ. The one, a living being, an actual man, and the second a life-giving Spirit, but importantly he is called the “the last Adam.” That parallelism is present in Romans 5 when Paul speaks of “the transgression of Adam, who was a type of the one who was to come.” (Rom 5:14) Adam, acting representatively is a type of Christ, who also acted representatively. A few verses lated, Paul says, “For if, because of one man’s trespass, death reigned through that one man, much more will those who receive the abundance of grace and the free gift of righteousness reign in life through the one man Jesus Christ.” (Rom 5:17) There is nothing mystical or figurative about Adam’s sin here. It is the trespass of one man. Since that trespass is real and its consequences could scarcely be more serious for Paul, it requires an historical Adam. The fact of Adam leads to the fact of the incarnation of the man Christ Jesus and his life-giving sacrifice. It was a true and real body he had that suffered on the cross and a true and real resurrection that justifies those who trust in him.
If we want a Savior whose sacrifice can be applied to the many, we need to see that Scripture likewise presents the first man whose sin applies to the many. To reject this is to reject a major thesis of apostolic doctrine about salvation. The early chapters of Genesis are not just about creation, but about new creation as well.