Longtime readers of The Economist, and you know you're out there, may recall the magazine's May 2011 cover story “Welcome to the Anthropocene.” The essay introduced many readers both to a neologism and to a new idea: that human beings have so profoundly altered the Earth's atmosphere, soil chemistry, and fossil record as to have left permanent physical evidence of their presence. Half a billion years from now, when humanity's other works have fallen to dust, alien or post-human scientists can look at the planet's geological record and say with certainty “Oh, yeah, those guys. Drama queens, the
