How do Catholics reconcile a metaphorical Adam and Eve with Original Sin It is known that many Catholics believe that Adam and Eve is a story better left to the metaphorical imagination, rather than literal interpretation (though other denominations may feel differently). Going off of this belief, wouldn't that imply that since it is just a metaphor, and not literal, that it never really happened, and if it never really happened, then there is no REAL original sin?

If it is a metaphor and there is no original sin, then why did Jesus come to earth? Why did he have to repent us of this non-existent sin?
Catholics cannot believe in a "metaphorical Adam and Eve" for at least these reasons:


The Fathers of the Church all taught that Adam and Eve were two, real people, the first parents of the entire human race (monogenism, contra polygenism, which says humanity has more than two first parents), and Catholics must interpret scripture according to the unanimous consent of the Fathers (cf. Council of Trent Session IV, the Decree concerning the Canonical Scriptures, or the First Vatican Council's Dei Filius).
The 1909 Pontifical Biblical Commission decided:



  The first three Chapters of Genesis contain the stories of events
  which really happened, i.e., which correspond with objective reality
  and historical truth (rerum vere gestarum narrationes quae scilicet
  obiectivae realitati et historicae veritati respondeant); no myths, no
  mere allegories or symbols of religious truths, no legends. D 2122.