So what really did cause the Maya to collapse? This group of scientists think it was the weather. By using a new technique to determine monsoon cycles over the past 16,000 years, scientists have found remarkable agreement between dates when monsoon rains were very poor and the decline and eventual collapse of two great prehistoric civilizations... the Maya and the Chinese Tang dynasty. As I recall, there actually are pretty good archaeological records which address climate change in these areas at these times. It'll be interesting to find out if they agree as well.