Q. Why did the Maya think the world was going to end on December 21st, 2012?
A. They didn’t. This date coincides with the end of a cycle of the Mayan calendar. You can read more about the Mayan calandar. Click here if you want to hear Arthur talk about the end of the world.
Q. Were the Maya and other ancient civilizations originated from space aliens?
A. No. See this post (Ancient Civilizations and Space Aliens) for explanations to the incredible claims of popular authors and tv shows.