Here is how I see Romans 5:12:
Wherefore, as by one man sin entered into the world, and death by sin...
From the moment he was created Adam was a physical model of perfection, but in his heart, he was just as carnal and spiritually immature as you or I. Sin did not just present itself when Eve lusted after the fruit and then took of it; it was already in her heart, just as it was already in Adam’s heart, even though he had not transgressed or gone against God’s commandment before Eve gave him the fruit.
How can transgression of God’s law or sin manifest itself outwardly if it is not already present within our heart? Mark 7:21-23 says:
For from within, out of the heart of men, proceed evil thoughts, adulteries, fornications, murders, thefts, covetousness, wickedness, deceit, lasciviousness, an evil eye, blasphemy, pride, foolishness: All these evil things come from within, and defile the man.
One cannot physically murder another unless the murder was not already present in his heart. Physical adultery does not occur unless one has already committed adultery in his heart. Everything comes from the heart. In like manner, neither Adam nor Eve would have transgressed God’s commandment if the sin had not already been in their hearts.
So, while the argument that Adam was the head of Eve and that he was to rule over her makes sense, for me it makes more sense to understand that Adam had sin in his heart from the very moment he was created, though he didn’t transgress the commandment until Eve gave him the fruit. That is how sin came into the world; because God created us, including the first man Adam, “subject to vanity” (Romans 8:20), subject to the lusts of our own hearts.
Thoughts?
Eric