Decades of extreme weather first weakened the Mayan culture and then killed off much of the population.
For the first time, researchers have combined precise climatic records of the Mayan environment with the culture's political history and discovered that a lack of rainfall preceded its collapse.
"Here you had an amazing state-level society that had created calendars, magnificent architecture, works of art, and was engaged in trade throughout Central America," says UC Davis anthropology professor Bruce Winterhalder.
"They were incredible craftspersons, proficient in agriculture, statesmanship and warfare - and within about 80 years, it fell completely apart."
The study took advantage of the extensive Maya Hieroglyphic Database Project, run by UC Davis Native American Language Center director and linguist Martha Macri and recording details of the culture's stone monuments.
Inscribed on each monument is the date it was erected along with the dates of significant events, such as a ruler's birthday or accession to power, as well as some deaths, burials and major battles. Unfortunately, they made no mention of ecological events, such as storms, drought or crop failures.
For this, the team collected a stalagmite from a cave in Belize, less than a mile from the Maya site of Uxbenka and about 18 miles from three other important centers. Using oxygen isotope dating in 0.1 millimeter increments along the length of the stalagmite, they uncovered a physical record of rainfall over the past 2,000 years.
And, thery found, periods of high and increasing rainfall coincided with a rise in population and political centers between 300 and 660 AD. But a climate reversal and drying trend between 660 and 1000 AD seems to havetriggered political competition, increased warfare, overall sociopolitical instability - and, finally, political collapse.
This was followed by an extended drought between 1020 and 1100 AD that likely brought crop failures, famine, migration and, ultimately, the collapse of the Mayan population.
"It has long been suspected that weather events can cause a lot of political unrest and subject societies to disease and invasion," says Macri.
"But now it's clear. There is physical evidence that correlates right along with it. We are dependent on climatological events that are beyond our control."