My new theory on religion:
Some evil dudes were sitting around discussing how they can cause the most people to be murdered. "I know, let's write a book detailing the origins of a fake religion, pass it off as a real religion, and watch the adherents kill half the population of the known world." And that's exactly what happened. Then, a millenium or so later, someone decided to do the same thing, but this time they called it the Koran.