The word anthropocene has been proposed to denote an ongoing epoch in which human activity is a primary driving force of geological change. Although the word has caught on like wildfire in a colloquial sense, it was ultimately rejected as a descriptive scientific term, not so much because it was inaccurate but because of disagreements over when exactly it would have started – 1945, marking the unlocking of nuclear power; 1610, which may be the first time human activity affected the amount of carbon dioxide in the atmosphere; 1964, when the so-called Great Acceleration may have begun – or some...