Discovery: The vast empires of the Incas and Aztecs were highly advanced. They kept detailed tax records, built elaborate temples, and at their height, Central and South America boasted a thriving population of as many as 60 million souls. But their grand civilizations bore another trapping of modernity, scientists have found, one that until recently was thought unique to our industrialized world: human-induced climate change. In the 16th century, the diseases Europeans brought to the New …