"The early Classic Maya period was unusually wet, wetter than the previous thousand years," according to study leader Douglas Kennett, an environmental anthropologist at Pennsylvania State University. "During this time, the population proliferated," aided by a surge in agriculture. But the 200-year-long wet spell turned out to be an anomaly. When the climate pendulum swung back, hard times followed.

"Mayan systems were founded on those [high] rainfall patterns," Kennett said. "They could not support themselves when patterns changed."

The Maya religious and political system was based on the belief that rulers were in direct communication with the gods. When these divine connections failed to produce rainfall and good harvests, tensions likely developed.

How did the environment impact Mayan survival?