"And Adam lived an hundred and thirty years. and BEGAT a son IN HIS OWN LIKENESS, AFTER HIS IMAGE: and called his name Seth."
Why is this important? Because Adam was created in God's image, without sin, until he ate of the tree of the knowledge of good and evil, and sin entered into him. THIS is where we get our sin nature, from the fallen Adam. We are begotten of Adam, fallen Adam, and our nature is of Adam, corrupted by sin. All of us. Until the second Adam, Jesus Christ took our sins.
The question is how corrupt ? Adam fell, but how far?