sighSomeone seems to be emotionally invested in believing it is this easy to disprove a religion.
Sorry for the rant I'm about to go on, but during my general linguistics studies I took Old Hebrew as one of my two required non-Indo-European languages. I eventually dropped/replaced it because it was less about the language than about the literature/theology, but some of that information is useful in discussions like this where people's views are just embarrassingly simplistic.
First of all, the Big Bang has no relevance to the original sin story. Genesis 1 (where the Big Bang does have relevance) is written in a different style from Genesis 2 (they use different words for God, for example). These were separate oral stories collated into 5 books. You can also see this in how Genesis 2 seems to retread part of what was already said in Genesis 1.
Second, the original sin story doesn't need to be completely literal, it only needs to convey a message. How exactly humanity got original sin and developed the concept of morality is irrelevant to the arguments and beliefs building on it. What is relevant is whether the results are true. Do you really think someone for whom this is part of their identity wouldn't just say "so what if it wasn't an actual fruit?" It's not even logically inconsistent.