Darwin's Lucky Break: The Rise of Complexity - Fluke

Okay, so, you know, in the last part of Darwin's *On the Origin of Species*, he's just blown away, right? By the crazy explosion of life, like, from the simplest, simplest beginnings to, you know, just "endless forms most beautiful," as he put it. And, like, that beginning really *was* simple. For, like, most of Earth's history, life was just kinda, stalled out, stuck as single-celled organisms. So, to get to, like, all the cool stuff – orchids, octopuses, I mean, even us, right? – we needed to get, like, super lucky. Not just, you know, everyday, run-of-the-mill lucky, but the kind of luck that, like, only hits, like, every few *billion* years, if that!

So, get this: until about two billion years ago, everything alive on Earth was just simple, tiny prokaryotes, right? Single cells without a nucleus, like bacteria and stuff. Then, like, for completely unknown reasons, some bacterium just, like, bumped into another prokaryotic cell and ended up *inside* it. And that bacterium, eventually, it evolved into a mitochondrion, right? The powerhouse of our cells. I mean, in that moment, everything changed! Every single species of complex life – trees, grass, snails, humans, you name it – owes its existence to this, like, totally unexpected microbial merger. It's kind of unsettling, isn't it? That the entire human story can be traced back to, like, a microscopic accident. Happened *once*, two billion years ago, and, like, never again. It's, perhaps, the greatest fluke of all time.

And when you look at the history of our species, there are tons of similarly crazy stories. They make it super clear that, like, our existence and the way we live is accidental, arbitrary, and therefore, precarious. Scientists even recently found out that the reason we don't lay eggs might go back to some, like, shrew-like creature getting infected with a retrovirus, oh, I don't know, maybe around 100 million years ago or something. And that led to the evolution of the placenta and, eventually, live births. I mean, the stories of our lives have, like, countless authors, human and otherwise, in this crazy collaboration across, like, huge distances and, like, way back in the past. But, you know, for just one small, seemingly random accident in the mists of time, none of us would even *be* here.

Now, this awe-inspiring fragility from way back in our evolutionary past, it might seem, you know, far removed from our lives today. But, our social world, it’s transformed, like, constantly, right? Moment to moment, year to year, by the arbitrary. I mean, because our world is so intertwined, where changing anything changes everything, apparently meaningless adjustments can show up in the most bizarre and unexpected ways.

Like, I’ve been going to Madagascar for my research. And a few years ago, I started seeing this new food, like, this delicacy, in food stalls on the side of the road. It's called *marmorkrebs*, marbled crayfish. They first showed up on the island maybe fifteen years ago, but in the last decade, they've, like, completely taken over! They're everywhere! But here’s the weird thing: nobody knows where they *came* from, really.

Scientists aren’t totally sure, but the theory is that the new species emerged, believe it or not, after, like, a single female crayfish went through some, like, freak mutation in an aquarium in a German pet shop, of all places, in, like, 1995. For reasons that are still mysterious, that pet shop crayfish changed in, like, crazy ways. Instead of having the normal two sets of chromosomes, she had *three*. And she didn’t need a male to get pregnant, either! This mutant crayfish could suddenly clone herself asexually, laying genetically identical eggs. So, every single marmorkreb after that was female. A genetic replica of the original mutant mother. Because of that weird ability to reproduce by herself, just one single marmorkreb can cause a population explosion, like it did in Madagascar.

Now, these marmorkrebs are an invasive species, and they love to eat rice fields. But in their millions, they've also provided some, like, totally unexpected benefits. A lot of Madagascar’s population is malnourished, like, lacking protein. The abundant supply of crayfish is now providing a cheap, steady source of, you know, delicious nutrition. And it looks like the marmorkrebs eat the freshwater snails that carry schistosomiasis, a parasitic disease that affects millions on the island. So, Madagascar's rice crops have been, you know, devastated, but thirty million people have a new food source and millions of kids are less likely to get parasites – all because of one single genetic mutation in a crayfish, probably in a German pet shop.

And it gets *weirder*. Researchers took two genetically identical marmorkrebs and put them in the exact same environments, and something crazy happened. Even though they were genetic copies and raised in the same place, their offspring were bizarrely different. One daughter grew, like, twenty times bigger than another! They had variations in their organs, and their behavior was totally different. One died after, like, 437 days. Another lived for more than twice as long. And, like, nothing genetic or environmental could explain these huge differences! So, what caused them? Nobody knows! It might have something to do with epigenetics, but scientists are stumped.

Random fluctuations can, like, spread out across time and space and cause unexpected opportunities or disasters, or both. I mean, millions of lives in Madagascar were changed by a mutation in one dead crayfish from Germany. There was no grand plan. It was just an accident, a random genetic mistake. And the effects of that accident were amplified because we're all so interconnected. Facing such unfathomable contingency, sometimes the best we can do is just, like, shrug and go with what that Scottish biologist, D’Arcy Thompson, said: "Everything is what it is because it got that way."

But, like, we're told over and over that "everything happens for a reason." And that kind of reassuring myth-making, it makes us make cognitive mistakes. We misjudge reality as we try to shove it into some neat, ordered pattern that makes sense to us. I mean, we tend to downplay the role of luck, you know? The word we use to describe the random and the accidental showing up in our lives. Like, think about the belief that the super-rich must have earned their wealth because they’re geniuses. Look a little closer, and, like, that myth just crumbles.

Most human traits, including intelligence, skills, hard work, they're normally distributed. You know, a bell curve. Wealth, though, wealth isn't normally distributed *at all*. It follows a power law, a Pareto distribution, with a tiny group of people controlling huge amounts of wealth. You'll never find someone who is five times shorter or five times taller than you, but today’s richest person is more than a million times richer than the average American. So, someone who is marginally smarter than you could become a million times richer, rather than just marginally richer. It's the world of "fat tails," right? Like, that Nassim Nicholas Taleb writes about in *The Black Swan*.

But, like, what if such extreme wealth isn't from talent, but from random factors, luck? There was a recent study where physicists teamed up with an economist and used computer modeling to create a fake society with a realistic distribution of talent. And, you know, in their fake world, talent mattered, but so did luck. Then, they ran the simulation over and over, and they found that the richest person was *never* the most talented. Instead, it was almost always someone, like, kinda average.

And why was that? Well, in a world of eight billion people, most people are in the middle of the talent curve. And luck, think of luck like lightning: it strikes haphazardly. So, because there are so many average people, luck is probably going to strike one of *them*, not the few, uber-talented geniuses. As the researchers put it, "Our results highlight the risks of the paradigm that we call 'naive meritocracy'... because it underestimates the role of randomness among the determinants of success." Some billionaires may be talented. All of them have been *lucky*. And luck is, by definition, the product of chance. Taleb, Duncan Watts, and Robert Frank have each shown how we tend to make up reasons after the fact when success is produced. They call it the "narrative fallacy" or "hindsight bias." The idea that billionaires *must* be talented is one of those fallacies.

But if luck is so important for success, that should change how we think about fortune and misfortune. If you think you live in a meritocratic world, where success goes to the most talented, rather than partly by accident or chance, then it makes sense to take full credit for everything you do well and blame yourself for everything you mess up. But if you accept that randomness and accidents are a big part of what changes our lives—and they are—then that will change your outlook. When you lose at roulette, you don't beat yourself up for being a failure. You accept the outcome and move on. Realizing that meaningless, accidental outcomes come from an intertwined, complex world, it's, like, empowering and liberating! We should all take a bit less credit for our wins and a bit less blame for our losses, I think.

We're especially prone to making up false explanations when something bad happens to us. We can't easily accept randomness when we get cancer or get into a car accident. Bad news has to make sense, right? It's impossible to move on without figuring out the reason for your suffering. It becomes a quest for meaning in what might have been a meaningless disaster. "Everything happens for a reason" is, like, a coping mechanism. You hear it most often when people lose their jobs, when they get blindsided by breakups, or when people die. It can help us make sense out of the senseless. It comforts us with the idea of a neat, ordered plan for everything, but, like, it isn’t true. It's a useful fiction. Some things—even important and maddening and horrific things—just happen. That's what happens in an interconnected, chaotic world. Accidents, mistakes, and arbitrary neutral changes create species, shape societies, and change our lives.

On the other hand, research has shown that people are happy to accept randomness or chance when they have something good happen to them, like winning the lottery. In those moments of surprising joy, we're, like, a dog at its own birthday party, not sure why chicken and cheese are suddenly everywhere, but happy to eat them without asking any questions!

But when we try to explain anything *important*, randomness and chance go right out the window again. Like, think about how we try to make sense of the differences between people. We almost always end up with a simple choice: it's either nature (genes) or nurture (environment, upbringing, experiences). But there's a third option that's often ignored. What if, like with the marmorkrebs, some of the differences between us are just accidental?

Behavioral geneticists have figured out that about half the variation between us is from our DNA. That leaves another half that's, like, developmental dark matter. The inexplicable stuff of life. Damien Morris, a behavioral geneticist at King's College London, says that our life paths can be subject to random chance. He tells a story about identical twins in a classroom. One looks out the window and sees a bird flying by, and that distracts them. The other twin is really into the teacher’s explanation of a poem, and they develop a lifelong love of poetry. Their college majors and career paths change, all because of a bird outside a window.

And that idea is being proven scientifically. It's becoming clear that random fluctuations start in brain development even before we're born, and those small changes can have a big impact on our lives. Researchers compared the behavior of genetically identical fruit flies raised in the same environment. They still found a lot of unexplained variation in non-inherited traits. These differences seem to be due to small, random differences in their neural wiring, small fluctuations during development that created a lifelong pattern. Our brains are similar to those of flies, so, while we can't do those experiments on humans, there's reason to think that our wiring also has random but consequential variations, even before we're born. No matter how much we pretend otherwise, we're sometimes just puppets of the accidental.

A lot of people don't like this view of the world. They say it's just "noise," fine for philosophers to think about, but not real. Maybe those random fluctuations just disappear over time. Sure, change happens according to structured patterns and order. So, let’s answer the main question once and for all: Is our world contingent or convergent? Does everything happen for a reason, or does stuff just happen?

In Hindu mythology, Chinese mythology, and some Native American stories, the earth is on the back of a giant turtle. There's a story where a boy hears that and asks, "What does that turtle stand on?" The answer is: the first turtle is on top of a second turtle. "And what does the second turtle stand on?" the boy asks. The answer is, "It's turtles all the way down."

"Turtles all the way down" is now, like, a shorthand for an infinite regress, where each explanation is on top of another, which is on top of another, forever. That's how contingency works. In a contingent world, you're the result of a nearly infinite web of events, arranged with just the right pieces to create you. Change any piece, no matter how small, and you disappear, becoming what Dawkins called the "unborn ghosts." Without that small change, everything could have been different. Contingency all the way down.

A lot of books imagine the "what-ifs" of history. But here’s the thing: we only have one Earth. We can't test hypotheses about other possible worlds. We can’t test counterfactuals by replaying time, rerunning events with small changes to see how history would be different. We’re stuck speculating.

In 1998, there was this movie called *Sliding Doors* that imagined we could see other possible worlds. The movie starts with Helen, played by Gwyneth Paltrow, trying to catch a train on the London Underground. She runs down the stairs but gets blocked by a little girl, costing her a split second. She gets to the train, but the doors close, and she misses it. Then, the tape rewinds about fifteen seconds and starts again. Everything seems the same, but this time the little girl’s mother moves her daughter out of the way. Helen squeezes onto the train just as the doors slide shut. The movie shows Helen’s life through both worlds, one where she caught the train, the other where she missed it. In some ways, Helen’s life is totally different. In other ways, her life goes towards similar results, even though her path changed. When you think about the movie, it becomes obvious that that's how our lives work, but we hardly ever think about it, maybe because it's too overwhelming to know that every moment matters. And unlike the filmmakers, we can't rewind, so we never know which of our "Sliding Doors" moments mattered the most.

Evolutionary biology is like the ideas in *Sliding Doors*. Do species rise and fall in predictable ways, whether they catch the evolutionary train or not? Or do small, unimportant changes and accidents change trajectories and create new traits, behaviors, and species? Evolutionary biology is a historical science that helps us think about change in general. So, it’s worthwhile to look at Darwin's world and use lessons from other flora and fauna to understand how our lives and societies change.

Darwin’s main idea was that the natural world creates "selection pressures" that decide, on average, who lives and who dies. If a group of birds with broad beaks lives on a rocky crag where food is only found in narrow cracks, they're more likely to die than those with narrower beaks that let them get food from those cracks. Over time, the narrower beaks are "selected" because birds that have them are more likely to live and have offspring, while the others will die off. Generation after generation, the species adapts to its environment, and if a finch with a narrow, spear-like beak is born, it will beat out the others in the evolutionary race. This continues until the environment changes, and the selection pressures for survival shift.

But for evolution to make sense, the earth had to be old, giving species time to experiment and adapt. For centuries, the idea was that the earth was only about 5,850 years old. (In the 1600s, Bishop James Ussher said the earth was created at 6:00 p.m. on October 22, 4004 BC.) That wasn't nearly enough time for evolution to work. If Rome wasn't built in a day, pigeons certainly couldn’t have evolved in six. Then, as geologists discovered that the earth was far older than they thought, evolutionary theory became believable.

Darwin couldn't understand the mechanism: that a microscopic chemical recipe creates variation within and between species. Decades after he died, evolutionary biology was shaped by an idea called the modern synthesis. It's a simple but powerful model that is useful for understanding social and cultural change within humans as well as shifts within and between species. Organisms mutate and random variations accumulate, which creates the genetic building blocks for trying to solve problems. (Today we know that random mutations occur when DNA gets copied, but Darwin died seventy-one years before the double helix was discovered.) Those mutations might create different beak types, some long and narrow, others short and broad. Then, natural selection does its work. Organisms with more useful traits live and pass their genes more, on average, to the next generation, while organisms with less useful traits die more often, on average, before they can reproduce.

Survivors decide the future. Ruthless, but effective.

But biologists disagree about whether evolutionary change is a smooth, predictable process or a jagged, unpredictable march defined by contingency. How suddenly does change happen? Those who say it's a slow and steady process are sometimes called "evolution by creeps." Those who say that evolution is mostly stable until a sudden shift changes everything are mocked as representing "evolution by jerks."

These debates matter for what we might call the "snooze-button effect." If the world is mostly convergent, then it won’t matter if you get out of bed five minutes later than you planned. But if the world is sometimes changed by small, contingent events, then each tap of the snooze button could change everything.

The natural world shows evidence for both ideas. On the side of contingency are creatures like the duck-billed platypus. It's a species of what the biologist Jonathan Losos calls "evolutionary one-offs." The platypus, a venomous egg-laying mammal with the bill of a duck, the tail of a beaver, and the feet of an otter, sweats milk out of its pores to feed its young. It's so unusual that when the first specimen was shipped to Britain in 1799, a leading anatomist said, "It naturally excites the idea of some deceptive preparation by artificial means." He looked, but didn't find any stitches holding other animal carcasses together into some duck-billed Frankenstein’s monster. Someone else said it was the offspring of an evolutionary orgy, "a promiscuous intercourse between the different sexes of all these different animals." Quite the hypothesis!

Or, consider the binturong, a bearcat native to South and Southeast Asia. Its urine contains a chemical called 2-acetyl-1-pyrroline. That chemical compound gives cooked popcorn its aroma. Binturongs tend to lather their urine on their feet and tail, creating a scent trail, so people who walk through the habitat of the binturongs often smell a movie theater lobby in the jungle. Evolution, through contingent events, can be rather strange.

Crabs are to convergence what platypuses are to contingency. King crabs, porcelain crabs, and hermit crabs are not true crabs, but unrelated crustaceans. Evolution has, on at least five occasions, turned animals into a crab-like body plan. It's so common that there's even a term for it: carcinization, which means "turning something into a crab-like form." (Some have said that the convergent force is so great that humans will eventually end up scuttling around with pincers!) Similarly, the ability to fly has evolved in at least four branches of the tree of life—in insects, bats, birds, and pterosaurs. Nature converges on similar solutions to common problems.

Our world moves between contingency and convergence, giving the illusion of structure and order, until one small change changes everything. With DNA sequencing, Mark Pagel, an evolutionary biologist at the University of Reading, found evidence that 78 percent of new species were created by a single event. Nature makes a random mistake, or a contingent deviation, and you've got a new kind of beetle.

But why does that matter to us?

Our understanding of human history is a fight between contingency and convergence. Do stable, long-term trends drive change? Or does history pivot on the smallest details? We can only speculate between the two worldviews because we can't test the past experimentally.

But what if you could create multiple worlds? And what if you could control what happens inside and also control time? Imagine being able to play God, pressing pause and rewinding whenever you want. That would give us a look at the mysteries of cause and effect with precision. We would finally know how change happens—and whether contingency or convergence is the truth. It's an interesting thought experiment. But could it happen?

A few decades ago, a scientist named Richard Lenski realized it was possible without science fiction. Lenski, who has a Darwin-style beard, had been working as an evolutionary biologist, studying the predatory southern ground beetle. He enjoyed the outdoors, but the work was slow, there were snakes, his beetles often drowned, and the complexity of the real world had so many variables that he couldn't test the ideas that he wanted to. Lenski started to wonder if experiments on evolutionary change could be run, not in the wilderness, but in the lab. In 1988, Lenski launched one of the longest-running and most important experiments in scientific history.

Lenski’s experiment is simple. Take twelve flasks, fill them with strains of E. coli bacteria, feed them the same glucose broth, and let them evolve. Because E. coli reproduce quickly, they pass through 6.64 generations per day. The average human generation lasts for 26.9 years, so one day in the world of these bacteria is like 178 years of human time. Since 1988, Lenski has seen evolution over seventy thousand generations of E. coli, the human equivalent of 1.9 million years of change. In 2004, Zachary Blount joined Lenski’s lab. Together, they have overseen twelve microbial universes, each in a flask.

I visited them so I could see these controlled universes. Lenski and Blount’s lab at Michigan State University is just a lab. There are beakers, cylinders, petri dishes, and bottles of chemicals on shelves. Next to the door, Lenski points out an incubator, set to 37°C, or 98.6°F, the same temperature as the human body. The incubator is humming as it shakes a flask of microbes. Despite its sterile look, the lab is obsessed with evolution. A poster of Darwin’s famous voyage is on the wall. A framed painting of a fantasy creature, upright like a man, but with octopus tentacles, is next to the light switch. Above it all is a banner with a phrase that inverts America’s motto, *e pluribus unum*, or “out of many, one.” In the Long-Term Evolution Experiment (LTEE), they follow a different mantra, an homage to evolutionary change: *ex una plures*—“out of one, many.”

I met Zachary Blount, the man who made that motto and banner, in an Indian restaurant near his lab in East Lansing, Michigan. He was easy to spot, with striped socks rising above his hiking boots. He’s a “twenty-first-century oddball” without a cell phone. Blount is usually found in a lab breaking the code of life’s secrets or thinking about those secrets while reading a history book at a campsite. He’s fascinated by flukes in microbial and human history. "Bacteria by day, Byzantine Empire by night," as he puts it. After spending four hours with him, I’m not sure I’ve met someone so curious or so thoughtfully productive at understanding the world.

Blount describes the experiment with excitement. Every day, the bacteria in each flask grow in a broth of glucose, or sugar, and citrate, the acid that gives orange juice its tang. The organisms swim in citrate, but can only eat glucose. Instead of having sex to reproduce, bacteria divide into two nearly identical daughter cells. Variation in the flasks mostly comes from mutations, or mistakes in DNA that occur during copying. The best thing about the experiment is that from one common ancestor, twelve different populations are free to evolve in identical conditions. *Ex una plures*. The experiment has eliminated sex, environmental change, and predators, allowing the scientists to see evolution at its purest. Lenski and Blount can therefore test whether contingency or convergence is the truth. If change is convergence, then the twelve flasks should only have minor variations even over long periods. They might take different paths, but they'll end up in the same place. That would mean evolution’s snooze button is meaningless. But if contingency dominates, the twelve populations should eventually diverge a lot, as chance creates microbial freaks, forever changing evolution’s path. One tap of the snooze button could change everything.

Lenski and Blount also have something most scientists don't: a time machine. E. coli can be frozen without harming it, so freezers act like a pause button. To press play, just thaw the bacteria out. From the beginning, Lenski and his team froze all twelve lines of bacteria every five hundred generations, so they could replay any part of the experiment from any time. Want to create a bacterial replay starting from the day the Soviet Union collapsed or from September 11, 2001? No problem. In those twelve universes of broth, Lenski and Blount control time.

For more than a decade, the experiment seemed to support evolutionary convergence. The twelve cultures were different, as small changes were unavoidable. But all twelve seemed to be changing in similar ways. Each lineage of bacteria was getting better at eating glucose, becoming more "fit" in the Darwinian sense. There was a clear sense of order. The specific mutations didn't seem to matter much. It was as though all twelve were following the same railway track, all racing toward the same destination. The creeps, not the jerks, were being proven right.

Then, one day, a postdoctoral researcher, Tim Cooper, arrived at the lab to take care of the twelve populations, as he'd done hundreds of times before. But this time, something was different. Eleven populations looked normal, "like flasks of water with a drop or two of milk mixed in, only their slight cloudiness indicating the millions of resident bacteria.” But the twelfth was completely different. It was partially opaque, a cloudy mixture when it should have been mostly transparent and clear. “I thought it was a mistake,” Cooper told me. “But I was pretty sure something interesting was going on.”

Cooper called in Lenski.

“I thought it was lab error,” Lenski told me. “Our motto in the lab to avoid contamination is ‘when in doubt, throw it out.’” Lenski decided to restart that line of bacteria from the last frozen sample. Thankfully, with their microbial time machine, mistakes could be corrected.

A few weeks later, the same flask turned cloudy again. There had been no mistake. Something was going on. The scientists sequenced the DNA of the E. coli in that flask and found something incredible. The bacteria had evolved the ability to eat the citrate they were swimming in, which shouldn’t have been possible. In the twentieth century, there was just one case of E. coli that could digest citrate. That it had now happened by chance was already an important discovery. But the story was about to get much more interesting.

To digest citrate, this “freak” line of bacteria had first undergone at least four unrelated mutations that provided no benefit to the population—seemingly meaningless errors. But if those four mistakes hadn't all happened, in that order, the fifth mutation, which gave them the ability to eat citrate, wouldn't have been possible. Five contingent mutations were stacked on top of each other, and they were improbable, too. Contingency all the way down.

Just how contingent were they? To find out, Blount spent years studying the freak population. He unfroze samples of the mutant lineage at different times, using the frozen bacterial record to test whether the ability to eat citrate would emerge again. After analyzing 40 trillion cells over three years, he replicated the citrate mutation seventeen times. But if he went back far enough into the bacteria’s evolutionary history, the citrate mutation never happened again. It was contingency, through and through. After seventy thousand generations—equivalent to 1.9 million human years of evolution—only one lineage out of the twelve has developed the ability to digest citrate. For one line of bacteria, one small change meant that everything about their future changed, all because of a random mutation, made possible by four unrelated accidents. The other eleven bacterial universes are stuck eating glucose, unaware that they are swimming in a “lemony dessert.”

Blount says that the Long-Term Evolution Experiment provides a way of thinking about critical turning points in human society. Many historians, for example, say that D-Day was the key to the Allied victory in World War II. If you could test that claim experimentally, historians would follow the same research design as Lenski and Blount. Imagine you had one thousand identical Earths and could pause them at different points throughout the war. If the Allied victory became more likely with worlds that started after D-Day, historians could say that D-Day was the turning point. But if the Allies won 75 percent of the time whether the world was thawed in June 1942 or June 1944, then it would be clear that the historians were wrong. D-Day didn’t matter so much. The Allies were always going to win.

Sadly, there’s only one Earth, we can’t rewind time, and these contingency versus convergence experiments are only possible with microbes in a lab. But, it seems that Lenski and Blount have resolved the contingency versus convergence debate: to us, the world looks convergent, until we realize that it isn't.

We’re often blind to the possible jolts until they happen. We follow routines, the world ticks on day by day, and small changes don’t seem to matter. The morning news comes on at seven. The commute takes twenty minutes. From our perspective, the creeps of convergence seem supreme.

But then, our lives—and our societies—change because of contingent events. Sometimes, these shifts are the result of lots of small changes. They build up over time until they reach a tipping point, and everything collapses. Other times, independent individual trajectories become causally linked. Imagine a fly buzzing around until it hits the eye of a motorcyclist, who swerves, crashes, and dies. The path of that fly mattered to the life of the motorcyclist, but he didn’t know the fly was important to his life until it was too late.

We, like Helen in *Sliding Doors*, are often unaware of how small, contingent changes change our lives and shift our societies. Some are random accidents, such as mutations in DNA. Others are decisions we make. They’re happening all the time. We tell ourselves that we’re in control of our lives. The truth is that everything is always changing, including ourselves. We live, as do E. coli, in a world defined by contingent convergence. There’s order and structure, but the snooze-button effect is real. That leads to a truth: every moment matters.

If contingent convergence is the truth, then why is randomness ignored in evolutionary change? Survival of the fittest seems to suggest a progression from worse to better. Natural selection is presented in a way that fits with the convergent “everything happens for a reason” way of thinking, in which it is assumed that evolution is so unforgiving that any evolved trait must have been shaped by nature’s hidden hand. Evolution works like “a miserly accountant, grudging the pennies, watching the clock, punishing the smallest extravagance. Unrelentingly and unceasingly.” Evolution corrects its errors in an optimizing process. In that view, there’s not just order and structure, but a goal: the world gets ever closer toward greater fitness.

Evolution can sometimes be more random. The rise of mammals was made possible by a giant space rock that wiped out branches of the tree of life. Evolution also follows random change through genetic drift, in which genetic variation in a population shifts due to chance. But biologists who have emphasized randomness and chance in evolution have been shunned. In discussions of evolution, we mostly hear about survival of the fittest, not survival of the luckiest.

You are alive today because of lucky individuals—evolution’s lottery winners—from the past. We are the descendants of genetic bottlenecks, which is a subset of genetic drift. Bottlenecks happen when genetic diversity plummets due to a loss in the number of individuals alive in a species. For example, people admire the northern elephant seals on California’s beaches. But during the 1800s, humans hunted that species nearly to extinction, until as few as twenty breeding pairs remained. Today, every elephant seal is a descendant of that small cluster. It matters which seals survived to regenerate the species.

Imagine something similar happening with humans, in which the entirety of our species was whittled down to forty people, before exploding to 8 billion individuals. The exact composition of those forty people would define the species. If all forty came from nurses and doctors at a children’s hospital, future humans would be different from what would happen if all forty were Kardashians. With such low numbers, every individual would reshape humanity. For better or worse, billions descended from a gene pool that began with one-fortieth Donald Trump would be different from the descendants of a gene pool that contained one-fortieth Malala Yousafzai instead.

This isn’t hypothetical. Humans had a population bottleneck thousands of years ago. One study said that there were as few as one thousand human breeding pairs. Other estimates suggest that there may have been around ten thousand humans left, which was itself an arbitrary subset of the human gene pool. From ten thousand to 8 billion, in an evolutionary blink. Human genetic diversity seems to have plummeted so much that modern chimpanzees on either side of a river in Cameroon show more genetic variation than modern humans living on different continents. All of our lives pivoted on those bottlenecks, an evolutionary accident of a snapshot in the ancient past. Without it, you wouldn’t exist.

Prehistoric migrations also meant that smaller, arbitrarily selected, populations “founded” different groups of humans that then developed independently in an area. These are called founder effects. Some genetic studies say that indigenous populations of the Americas may have been established by between 70 and 250 individuals who crossed the land bridge from Asia. On the islands of Tristan de Cunha, 150 of the 300 residents have asthma because the island was settled by fifteen people (many of whom had asthma). The dodo emerged from a founder event, when a group of pigeons landed on Mauritius, put on weight, and lost the ability to fly. No hidden purpose guided the islanders or pigeons. They were just accidents.

These ideas are related to survivorship bias, in which we can only see that which has survived. Much of our knowledge of cavemen comes from cave paintings. It's possible some didn’t live in caves and painted on bark, so we should think of them as treemen. But the trees are gone, so we can’t say, while the cave paintings survived. Similarly, classical thought has influenced modernity, but our interpretation of it is influenced by an arbitrary factor: which ideas survived through manuscripts while others were lost to history. Aspects of human history are arbitrary.

Yet, the image of nature as an optimizer stays. Daniel S. Milo says that the world is full of “good enough” solutions, which others call a kludge approach. (A kludge is “an ill-assorted collection of parts assembled to fulfill a particular purpose.”) We all find out that the human knee or the human lower back mostly do their job well enough, but few would call them optimal. Motoo Kimura was one of the few to show how evolutionary change was driven by accidents. His neutral molecular theory has shown that randomness drives change at the molecular level. Yet few outside of evolutionary biology have heard of him or that idea. With small changes, so much could turn out differently. It’s true in evolution, but in our lives and societies. Everything doesn’t happen for a reason.

Random fluctuations have upsides. Evolution provides a lesson: undirected experimenting is essential. In a changing environment, a trial-and-error approach lets us find the best path. With experimentation, we discover the joy and wisdom of life's flukes.

In 2014, workers on the London Underground went on strike. Commuters were affected. It forced them to experiment. Using data, economists examined 200 million data points, both before and after the strikes. Many people stuck to the route they were forced to use. They had been unaware of a better route