Some things occur just by chance. Mark Twain was born on the day that Halley’s comet appeared in 1835 and died on the day it reappeared in 1910. There is a temptation to linger on a story like that, to wonder if there might be a deeper order behind a life so poetically bracketed. For most of us, the temptation doesn’t last long. We are content to remind ourselves that the vast majority of lives are not so celestially attuned, and go about our business in the world. But some coincidences are more troubling, especially if they implicate larger swathes of phenomena, or the entirety of the known universe. During the past several decades, physics has uncovered basic features of the cosmos that seem, upon first glance, like lucky accidents. Theories now suggest that the most general structural elements of the universe — the stars and planets, and the galaxies that contain them — are the products of finely calibrated laws and conditions that seem too good to be true. What if our most fundamental questions, our late-at-night-wonderings about why we are here, have no more satisfying answer than an exasperated shrug and a meekly muttered ‘Things just seem to have turned out that way’?
It can be unsettling to contemplate the unlikely nature of your own existence, to work backward causally and discover the chain of blind luck that landed you in front of your computer screen, or your mobile, or wherever it is that you are reading these words. For you to exist at all, your parents had to meet, and that alone involved quite a lot of chance and coincidence. If your mother hadn’t decided to take that calculus class, or if her parents had decided to live in another town, then perhaps your parents never would have encountered one another. But that is only the tiniest tip of the iceberg. Even if your parents made a deliberate decision to have a child, the odds of your particular sperm finding your particular egg are one in several billion. The same goes for both your parents, who had to exist in order for you to exist, and so already, after just two generations, we are up to one chance in 1027. Carrying on in this way, your chance of existing, given the general state of the universe even a few centuries ago, was almost infinitesimally small. You and I and every other human being are the products of chance, and came into existence against very long odds.
And just as your own existence seems, from a physical point of view, to have been wildly unlikely, the existence of the entire human species appears to have been a matter of blind luck. Stephen Jay Gould argued in 1994 that the detailed course of evolution is as chancey as the path of a single sperm cell to an egg. Evolutionary processes do not innately tend toward Homo sapiens, or even mammals. Rerun the course of history with only a slight variation and the biological outcome might have been radically different. For instance, if the asteroid hadn’t struck the Yucatán 66 million years ago, dinosaurs might still have run of this planet, and humans might have never evolved.
Written By: Tim Maudlin
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