“Say the planet is born at midnight and it runs for one day. First there is nothing. Two hours are lost to lava and meteors. Life doesn’t show up until three or four a.m. Even then, it’s just the barest self-copying bits and pieces. From dawn to late morning—a million million years of branching—nothing more exists than lean and simple cells. Then there is everything. Something wild happens, not long after noon. One kind of simple cell enslaves a couple of others. Nuclei get membranes. Cells evolve organelles. What was once a solo campsite grows into a town. The day is two-thirds done when animals and plants part ways. And still life is only single cells. Dusk falls before compound life takes hold. Every large living thing is a latecomer, showing up after dark. Nine p.m. brings jellyfish and worms. Later that hour comes the breakout—backbones, cartilage, an explosion of body forms. From one instant to the next, countless new stems and twigs in the spreading crown burst open and run. Plants make it up on land just before ten. Then insects, who instantly take to the air. Moments later, tetrapods crawl up from the tidal muck, carrying around on their skin and in their guts whole worlds of earlier creatures. By eleven, dinosaurs have shot their bolt, leaving the mammals and birds in charge for an hour. Somewhere in that last sixty minutes, high up in the phylogenetic canopy, life grows aware. Creatures start to speculate. Animals start teaching their children about the past and the future. Animals learn to hold rituals. Anatomically modern man shows up four seconds before midnight. The first cave paintings appear three seconds later. And in a thousandth of a click of the second hand, life solves the mystery of DNA and starts to map the tree of life itself. By midnight, most of the globe is converted to row crops for the care and feeding of one species. And that’s when the tree of life becomes something else again. That’s when the giant trunk starts to teeter.”