Yes, and no. I can't speak for laws in the USA, as I'm from Europe. But Copyright-laws in the EU do have parts which specifically target mixing and mashups of content, and how much new content of your you need to add to make it count as a separate work. These parts were recently updated, because of YouTube, the meme-culture and so on. But it's my understanding that for music and text-quotes, the whole concept is already longer around. So I guess US-Laws do have something like this too?
So of course, this does not handle novelty on a global scale for all of mankind's knowledge and content, but the general Idea and how to handle it is there.
> Two people can independently create the same thing and both be entitled to copyright.
Similar maybe. But for literally the same, I doubt it. People are getting already sued for having too much similarity.