Archaeologists have long debated why Maya communities in the Southern Lowlands suffered a period of widespread sociopolitical upheaval between a.d. 800 and 1000. During what is known as the Terminal Classic Period, dynasties collapsed, urban centers were abandoned, and populations dwindled, bringing an end to the Classic Maya civilization. According to a statement released by the University of Cambridge, potential new clues to the causes of this phenomenon have recently been identified in the Grutas Tzabnah cave in Mexico's Yucatán. Researchers analyzed oxygen isotopes in cave stalagmites that provided information about specific rainfall amounts during both the wet and dry...