I agree that Adam and Eve were considered married, although, they didn't have much of a ceremony.
Genesis 3:8 Then the man and his wife heard the sound of the LORD God as he was walking in the garden.... (NIV)
NASB, KJV, and other translations have it translated Wife. Although the sentance structure is different.
The original Sin - There are a couple of things that happened when Adam and Eve ate the fruit.
1st - Eve embelished, and obviously had a feeling that God was being unfair, her statement was:
"But of the fruit of the tree which is in the midst of the garden, God hath said, Ye shall not eat of it, neither shall ye touch it, lest ye die."
Genesis 3:3 KJV
Eve added the touch it part. Why? Only she knows. But God never said that. I'm sure Adam and Eve could have played catch with the fruit, built a fort with the fruit... whatever... just not eat it.
2nd - Eve believed the Serpent, and didn't believe God.
Pretend you tell a friend not to go into a room.
Someone else tells your friend to go into the room.
If your friend goes into the room, they have chosen not to believe you. They have also basically called you a liar. Eve and Adam must have believed that God was a liar, or they wouldn't have eaten the fruit.
Side note - Don't think Adam was innocent, Adam had seen the fruit before. It's not like Eve walked up, showed him a fruit he didn't recognise, and he ate it without question. He probably knew exactly what he was eating.
3rd - Adam and Eve gained somekind of knowledge. Knowledge of Good and Evil. What does that mean? I don't know, I could guess, but all I know is that it couldn't be given back. It couldn't be taken away. This is the reason that Adam and Eve had to be removed from the Garden.
Genesis 3
22 And the LORD God said, "The man has now become like one of us, knowing good and evil. He must not be allowed to reach out his hand and take also from the tree of life and eat, and live forever." 23 So the LORD God banished him from the Garden of Eden to work the ground from which he had been taken.
Whatever Adam and Eve gained that day, seperated the human race from God. Is it this that is passed on?
God could not allow Adam and Eve to live forever. Why?
If God had allowed Adam and Eve to live forever, they would have been forever seperated from God. Death is the price of Sin. Through the Death of Jesus we can be reunited with God.