Hello Winston, this is a good question and one that I do not have a certain answer for. I am of the opinion it is possible it might be literal fact or it might be myth, and we can not know that unless we know where the information originated. If the information originated with Adam and Eve and transpired generations then there are questions about why historical and archaeological evidences indicate a conflicting timeline. But those can be answered with assumptions that the bible does not give information about. On the other hand if it is fictional then there are other questions, for example, why did the author go to such lengths to make it seem factual? I have in mind the genealogy giving detailed account of time passed from Adam to Moses, and then to king David.
So because of the possibility that either might be true, I sometimes consider it to be factual and other times consider it to be fictional. This gives me the ability to gain from considering it both ways.
You have asked a question based on the assumption that it is fictional:
If Adam, Eve, the apple, serpent, etc. Are symbolic, then what was the event that allowed sin into the world? And why were women punished more severely by god if Eve eating the apple didn't actually occur?
I remember the scriptures describing that Eve was convinced she would gain wisdom that would give her an advantage similar to God, so she began to eat the fruit that would give her knowledge of good and evil. When we consider what knowledge is, it is an understanding based on information, that equips us to more accurately manage actions to achieve what we desire. So to do this, to actually obtain and apply (which is the action described by symbolically taking fruit and eating it), it requires that information about good and evil is aquired, the effects of it assessed, evaluated for value, tests performed to ensure a reliable understanding of how it behaves. The scriptures show that after Eve began eating it, she gave some to Adam and he began eating it too. I am drawing deliberate attention to the point that they began eating it, of which there is no indication they stopped eating it, when viewed symbolically this way.
What I gather about the curse is more of a change of perception rather than a change of the operation. Adam no longer saw the world as a garden where he could walk around and eat fruit from any tree, but a place where he has to toil and labour to produce his food, and that thorns and thistles would be a constant plague. The difference being the way he looked at his daily duties. Eve in a similar way began to resent child birth, because it was painful and not so miraculous as it should be, since the one causing it to her would be demanding and sinful and would likewise learn about good and evil, to apply that knowledge against her sometimes.
