Humans have had such a huge impact on the Earth that some geologists think the human era should be enshrined in the official timeline of our planet. But some researchers say, wait a second — humans actually began to transform the planet thousands of years earlier, with the development of agriculture. “If the Anthropocene began in 1945, then the entire story of changing the surface of the earth by cutting forests and plowing prairies occurred before the Anthropocene,” points out Bill Ruddiman, a climate scientist at the University of Virginia. “Does that make sense?...