One of the many reasons that we are constantly re-telling stories that have already been told is a phenomenon known as ‘cryptomnesia‘. A lot of the time we re-use stories and tropes consciously as certain ideas sell well and because frankly, everything has already been done before. On other occasions, similarities can be found within content that is not consciously copied or replicated from content that already exists – however this may not simply be a ‘coincidence’. We each keep memories at the back of our brains that we forget about or repress. Sometimes, these memories reappear, but we don’t realise them as the memories they are – instead we believe they are new experiences or thoughts. So if we come up with an idea that we eventually realise already existed, there is a chance we have a memory of the already existing story that we forgot about.
This is arguably one reason as to why films, tv shows and books seem to be ripping off, or even ‘plagiarising’ other works that existed before them. While it is undeniable that the media industry is purposefully re-using old content (the most obvious examples being Disney using old fairytales and Marvel or DC films adapting comic books), there are a lot of less-obvious, subtle similarities to old works that may not have been intentional. Funnily enough, as a society we seem to think that completely re-creating old ideas in the form of ‘adaptation’ is okay, but accidentally finding small similarities to other works is not.
It all comes down to the fact that everything has been done already. In some cases, we may never know the exact extent as to which an idea we come up with is ‘original’ or not.