A major Reformed distinctive is the teachings of Scripture as relates to Adam's federal headship of all his progeny such that when he sinned all mankind was plunged into sin and corruption. This is commonly referred to as the doctrine of original sin.

But this is what happened:

When Adam transgressed, man was sealed to "vanity" [Rom 8:20 KJV], something *Adam was unwillingly subjected to at the outset in order to present to him a way by which he would have to decide who would rule his disposition, either God would or his own flesh. God needed to know where his allegiance fell. It was set up by God with the hope of success that he would choose God that God could then further him along in His purpose to bring him into union with Himself. Other examples of this way of God's proving can be seen in His dealings first with Cain, Abraham, Moses, Saul, David, and then there was, Jesus.

*Rom 8:20 KJV.

Read Romans 7 in that light and make application.