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
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