Sigh, you sound like some Jesuit. 

Sir, again, please put down the Ray Brown/Charlie Curran/Hans Kung theology book and read a real theologian.  

Yes, sir, the human race stands and falls together.  We are all connected in a mystical sense, such that what one does effects someone else.  Adam and Eve, our first parents were the original head of the human race.  When they sinned, they passed on their sinful nature to their off spring--whether spiritual or biological.  Whatever the case may be.

Jesus, is the new Adam.  Jesus is the new head of the human race.  When we are incorporated into Christ through our Baptism, we become part of his body.