12 Therefore, just as sin came into the world through one man, and death through sin, and so death spread to all men because all sinned— 13 for sin indeed was in the world before the law was given, but sin is not counted where there is no law. 14 Yet death reigned from Adam to Moses, even over those whose sinning was not like the transgression of Adam, who was a type of the one who was to come.
Many have taken Romans 5:12-14 to mean that Adam “sinned for the entire human race” based on the phrase in the passage above “Just as sin came into the world through one man.” However, the misleading belief of the “imputation of Adam’s sin” stems from misunderstanding what this verse is actually saying. The sinful nature is indeed passed down through the male line because Adam sinned deliberately as opposed to Eve, who was deceived (although she was still without excuse). So, it depends on what a person means when they say Adam brought sin into the world. Where some go wrong is to assume that Adam sinned for us, as if we are all guilty because of a sin that he committed. That is like saying the whole human race is guilty of murder because one man murdered, which is absurd. A person is only guilty of physical murder if they did it themself (not because, for example, Cain did so long ago).
On the contrary, we are all sinners by and immediately at birth (the true meaning of sin coming into the world through one man) because the flesh brought forth by Adam and Eve through cohabitation (although it is God who creates all of us) and then physical birth was naturally corrupt because Adam and Eve’s bodies were cursed (because of their sin) and no longer perfect. Imperfect flesh will only create imperfect offspring. Adam and Eve both sinned so that their physical bodies were now contaminated. Therefore, all of us, their children who came afterward, would enter this world as sinful beings. Adam’s sin resulted in his physical flesh producing more physical flesh that would possess sinful natures at birth.
It is for these reasons that the birth or incarnation of Christ had to come about by the Spirit’s agency instead of the physical seed of corrupt human flesh which would result in an imperfect being. Christ was and had to be perfect. Therefore, He could not be born by human will or seed. The Spirit formed Him within Mary to avoid passing the sinful nature onto Jesus through human reproduction.
30 And the angel said to her, “Do not be afraid, Mary, for you have found favor with God. 31 And behold, you will conceive in your womb and bear a son, and you shall call his name Jesus. 32 He will be great and will be called the Son of the Most High. And the Lord God will give to him the throne of his father David, 33 and he will reign over the house of Jacob forever, and of his kingdom there will be no end.” 34 And Mary said to the angel, “How will this be, since I am a virgin?” 35 And the angel answered her, “The Holy Spirit will come upon you, and the power of the Most High will overshadow you; therefore the child to be born will be called holy—the Son of God.