Paul never examined the subject nor did he ever read the Gospels, some of which were written after his death.  He was familiar with the sacrificial victim model and never strayed from it.  He had no reason to examine it.  Neither had access to modern scriptural scholarship, assuming that the Torah really was written by Moses and put into the Ark of the Covenant just before he died.  Neither certainly had any access to Darwin (and if you reject Darwin, just go away).  They thought Adam and Eve were real people and not archetypes and that the sin was defiance (and to an extent it was) rather than seeking the knowledge of who was doing good and who was doing evil, essentially blame, which is reserved to God.  This fits beautifully, by the way, with what Christ taught about the requirement of forgiveness (to be forgiven), which is different from salvation, which was to escape our old selves and the pain of sin (which Christ experienced in the abandonment of the Cross, which is our salvat,.