Thus, you create a new world. After that, you would probably mess around with it.... (blow stuff up, build stuff, etc.) After a while, you should feel bored about playing the world and decide to delete it. It says that you cannot get your world back once you delete it, but you don't care and press delete. You might think the world is long gone, which is true... but there is a possible chance of one in a million that your deleted world will be used by someone else. Once your world is deleted and someone else decides to create a "New World", they might have the possibility to join that "once deleted" world. They might spawn in another different location and never notice that their newly "created world" was once used by someone else.
To support this theory, we have found a video on YouTube that says, "Very Strange House In Minecraft That I DID NOT Build..." This dude has found an abnormally huge house that was reported to be built on top of a chunk error cliff. It is said that he couldn't find his local spawn point and discovered a building with many caves. It is also said that he never built the house and heard many death sounds of different mobs.
There have been numerous explanations about this.... Some people believed that Herobrine was responsible for the work. However, many others believed that another player was in the world before the person joined (or should I say, "created). The Other Player was said to delete the world until it was transferred to another player which is the person who recorded all this crap. Why so many chunks and glitches? Most people believe that the world didn't fully get transferred and was poorly generated. (since the people believed that the world was passed on to different players)
What do you think people? Could this possible theory be true? You might even have a world that might've been previously used by someone else.... All you have to do is discover and find out....