UXBENKA, Belize — What happened to the ancient Mayan civilization is a mystery. Archaeologists have theorized about it over the years, but no one knows for sure. Plausible causes of the decline of Mayan society are warfare, disease and social unrest, over-farming and climate change.

In November, the journal Science published new evidence and a theory about the possible cause of the decline. The theory, although not entirely new, posits the idea that the decline was the result of changes in the global weather patterns. The study leader is Douglas J. Kennett, a Penn State University anthropologist.

In addition to decline, the study also posits that altered weather patterns led to a rapid rise in the society, initially the result of increased rainfall. This rainfall resulted in a population increase and a high agricultural output.

To bolster the theory, the researchers cite data from a 13,500-year-old cave stalagmite found on the floor of a recently discovered cave in Belize called Yok Balum.

A stalagmite is the result of rainwater and moisture dripping from the ceiling of a cave. Over time, the dissolved minerals in the water build up, forming a mass of mineral on the floor of the cave.

The findings allowed scientists to document what they say is a “precise record" of rainfall in the general region dating back 2,000 years. The measurements were obtained by analyzing the ratio of atomic isotopes along the length of the stalagmite. Researchers were then able to determine how much rainfall occurred in approximately six-month increments.

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The writers of the new theory say that in the early days of Mayan society, an increased rainfall provided an agricultural and population boom starting around 440 A.D. Kennett said, “This led to the proliferation of cities like Tikal, Copan and Caracol across the Mayan lowlands.”

The research suggested that by 700 A.D. the wet weather “began a drying trend that lasted for four centuries and was punctuated by a series of major droughts." The researchers said the drought triggered a decline in agricultural productivity and contributed to societal fragmentation and political collapse. They said the Mayan kings lost their power and influence.

In support of their theory, the researchers cited a general drought in Mexico that occurred in the 16th century that resulted in crop failure, famine and ultimately death throughout the region. Kennett and his colleagues postulate that a similar destruction was evidenced by the finding during the Mayan Classic period from 250 to 1000 A.D.

But the theory has its critics. Boston University archaeologist William Saturno is credited with the discovery of several new Mayan writings that predated and contradicted the “Mayan doomsday predictions.” His research was published and documented earlier this year in the National Geographic magazine. He is critical and skeptical about the new theory.

Saturno said the new evidence is unconvincing and that climate change was not the driver of the civilization's collapse. Saturno said the worst drought detailed in the report was in Belize 100 to 300 years after the Mayans.

Essentially, he said “they went dark” when they stopped inscribing monuments. Saturno also said that the Mayan civilization was diverse and included parts of present day Mexico, Guatemala, El Salvador and Honduras. The drought theory does not accommodate that diversity, he said.

Saturno told the Los Angeles Times, “Oftentimes, we’re looking at ancient societies as an analogue (similarity) to our own. We want to drive home the point: if we destroy the environment, we’ll reach a point where we can’t recover.”

Mel Borup Chandler lives in California. He writes about science-related topics, technological breakthroughs and medicine. His email address is mbccomentator@roadrunner.com.

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