Drought Believed Responsible For Mayan Collapse

A team of international researchers has found evidence that a significant drought that swept across Mexico roughly 1,000 years ago was a defining factor in the demise of the ancient Maya civilization. In new research published in the journal Science, scientists from the universities of Cambridge and Florida detailed their evidence showing that a long period of drought had devastating effects on the area.

The downfall of the great Mayan society has been the source of much debate. The Maya people flourished across Central and South America for nearly 3,000 years, with their civilization reaching its height around 800 AD. They built spectacular pyramids and temples and were notable for having the only fully developed written language of the pre-Columbian Americas. The Maya also developed highly advanced mathematical and astronomical systems, using astrological cycles to guide their everyday lives.

This incredible civilization had collapsed by 1000 AD. By the time Spanish conquistadors were exploring the Americas in the 16th century, jungle vines and wildlife had claimed the abandoned limestone cities. Suggested factors for the collapse have included war, invasion, pandemic illness, and the loss of trade routes.

Nick Evans, a PhD student in Cambridge’s Department of Earth Sciences, and his team decided to explore whether they could prove that extreme drought was also a factor. The researchers took sediment samples from Lake Chichancanab on the Yucatan Peninsula to calculate the conditions in the region at the time of the decline. They looked at the composition of the water trapped within the crystalline structure of a mineral called gypsum to build a model to estimate past changes in rainfall and relative humidity.

The water trapped in the gypsum crystals contains the different isotopes present in the lake water at the time of its formation. During times of drought, the lighter isotopes of water evaporate faster, leaving a higher proportion of heavier ones. Analyzing the isotopes present in the crystals let the researchers work out precise values for changes in rainfall and humidity in the area hundreds of years ago.

The researchers found that annual precipitation decreased between 41 percent and 54 percent during the period of the Maya civilization’s collapse. At some points, they found periods of up to 70 percent rainfall reduction. It is important to note that the Maya people never disappeared. Today, their descendants form sizable populations throughout Honduras, Guatemala, and western El Salvador.

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