Matt_dk writes: For 1200 years, the Maya dominated Central America. At their peak around 900 A.D., Maya cities teemed with more than 2,000 people per square mile — comparable to modern Los Angeles County. Even in rural areas the Maya numbered 200 to 400 people per square mile. But suddenly, all was quiet. And the profound silence testified to one of the greatest demographic disasters in human prehistory — the demise of the once vibrant Maya society. What happened? Some NASA-funded researchers think they have a pretty good idea.