HEN ALIENARCHAEOLOGISTS dig through the rubble of our cities and survey our planet’s ravaged lands and waters, searching for clues to the global catastrophe that wiped out half the species on Earth, what will they notice? The carbon-charged atmosphere, the layer of radioactive debris, a worldwide taint of manufactured poisons, vast middens of rubbish marking abandoned settlements, a scum of plastic on the oceans, bleached corals, oil-saturated wetlands, drained aquifers, silted reservoirs, craters from exhausted mines, and forests reduced to cemeteries of stumps. What a waste, the aliens will think, to ransack a planet so well suited for life. Belonging to a species wise enough to avoid trashing their own home, they will sift through
