University of Alberta geologist and project leader Colin Cooke holds a sediment core retrieved from one of several mountain lakes near Huancavelica, Peru, home to the world's second largest mercury deposit.

Cooke's team analyzed mercury pollutants in several cores to create a time line of mercury mining, from the Chavin culture through Inca and Spanish-colonial times to the industrial era.

By 1450, long after the Chavin had collapsed and as the Incas were expanding their reach, the type of pollution recorded there shifted from cinnabar dust to mercury vapor, Cooke's May 2009 study shows. This suggests the mercury was being heated, though it's unclear why.