Paleoclimate. A variable sun and the Maya collapse.
Kerr
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D001106:Archaeology; D002962:Civilization / Q000266:history*; D002980:Climate; D003468:Cultural Evolution; D004190:Disasters / Q000266:history*; D019015:Geologic Sediments / Q000032:analysis; D049690:History, Ancient; D008800:Mexico; D010507:Periodicity; D019445:Solar Activity