1. THE FALL

Imagine a frog. One of those lime-green tree frogs that cling to slim branches and stare out with dinner-plate eyes. Now imagine the frog is red. Bright red, like a stop sign. Give it wings. Watch the frog let go of the branch and fly away, red legs dangling. Some experts argue that other animals can’t imagine like this, piecing together information into something that does not exist. Perhaps this, they say, is what separates us from them. This and the ability to plan for a distant future, to envision a reality that does not yet exist and make steps toward it. They say nothing, however, of a future that presents itself in spite of the plans we lay out.

 

I didn’t see her fall. Or don’t think I did. I remember a forest of evergreens silhouetted black against the moonlit sky. My breath hung in the air, white against the trees. I was eleven years old, a stork of a girl well into braces and bony knees, and a few moments before, my mother had held my gloved hand in hers while we skated side by side. I leaned into the anchor of her grip and tested my legs; she matched her strides to mine. I let go of her hand and set off on my own. Skaters zipped by with scarves flapping and cheeks ruddy with cold. The outdoor rink, which had been erected on a frozen lake, was a tiny circus ring in the middle of a vast wilderness. The pocket of light was filled with tinkling laughter and the clean slice of metal across ice. Gradually, I lost track of my mother.

I’m not sure what happened. There was just a moment when I noticed, while gliding around the curve at one end of the rink, that skaters at the opposite end were slowing around someone lying on the ice. I drifted toward them, the skates heavy at the ends of my legs. Halfway there I saw the person on the ice was my mother.

As my father led her off the lake to sit down, she said she felt dizzy. She seemed confused and uncertain, shutting her eyes against the glare of the artificial lights. But no one called a doctor. Certainly not an ambulance. It was just a slip and a bump on the head.

 

I have begun to think that the human head is not the safest place to house the human brain, the organ that allows us to taste our favorite foods and wonder about the breadth of the cosmos; that fosters the euphoria of new love and sustains the ache of lost love; that enables our awareness of the body moving through space and the whole art and architecture of the self. The head perches on the pliable stem of the neck, far above the whole upright, two-legged balancing act of the body. It’s prone to snapping back and forth, is exposed to falling objects, and is likely to hit the ground—or things along the way—when we have trouble with balance.

The tissue of a living brain is soft, like custard. Put a finger to it and it gives. Blast a bullet through it and it splatters. Removed fresh from the skull, a human brain will quickly succumb to the pull of its own weight, slumping out of shape like warm Jell-O. This fragile mass is protected from the outside world by only a few millimeters of skull. Anything that meets the head with enough force can be devastating: shock waves, a car windshield, concrete, ice.

Despite its myriad powers, most of us take the brain for granted until it breaks down, noticing normal function only in its absence.

 

Looking at family pictures taken over the holidays after she fell, I can see that my mother’s face is swollen—it looks as if she might have been punched in the jaw. She doesn’t look well, but it’s hard to name what might be wrong. “Seasick” is the best I can do. She looks seasick. At the time, it didn’t occur to me that there might be something wrong with her brain.

 

The living brain is a lucent pink, not the gray of those lifeless oddities floating in glass jars. Living tissue is marbled with the blue of blood vessels that wind along blushing folds of cortex like rivers along canyons. Underneath lies a jigsaw of subcortical structures whose names ring with the confidence of scientific precision—thalamus, basal ganglia, substantia nigra. The threads of individual nerve fibers are bundled into ropy tracts woven throughout the brain, passing information from one brain area to another, from the spinal cord out into the body, from the body back up to the brain. The whole organ is awash in a churning soup of hormones and neurotransmitters, electrical and chemical activity shifting through it like fast-motion weather patterns.

Researchers are still chasing the brain’s patterns of architecture and activity with the imperfect tools of modern science: theory, experiment, data. But the mystery remains: How do sensation, thought, emotion, memory—a self—arise from a few pounds of tissue? The history of our attempts to answer this question is the story of our desire to understand what it means to be human.

 

At first there are photographs, and in every one my mother wears the same strange expression. It’s the look of a puppy given too many commands at once. Her smile is wide but her eyes are uncertain.

Then she stopped letting people take photographs of her. She would bow her head and step out of the frame, away from the eye of the camera.

 

What no one could see as the back of her head slammed against the ice was the force of the fall rippling through her brain. The sudden deceleration compressed precious brain tissue toward the back of her skull, rotating and distorting her brain, then smashing it against the curved back wall of bone, which may have dented inward like a rubber ball bounced against pavement. In an instant, an unknowable number of brain cells was crushed, and others were stretched or torn. While a more shock-absorbent surface—a foam mat or field with long grasses—might have mitigated the force of the fall, the ice was unyielding. After that first impact, her head bounced up off the ice and pressure waves ricocheted forward through her brain, rotating and distorting it once more, compressing neural tissue toward her forehead, where the front of her brain crushed up against her skull roughly opposite the first point of impact. This injury is known as coup-contrecoup, blow-counterblow, and the damage it describes is not limited to two bruised patches of cortex. Powerful rotational and shearing forces can injure areas throughout the brain. As the whole organ shudders like Jell-O in the cranial cavity, the long strands of nerve fibers that wind through it like millions of microscopic strings get twisted and pulled. Some are strained; others snap. A cruel oversight of evolution has left the floor of the human skull just above the eye sockets ridged rather than smooth. When the brain is forcefully moved inside the skull, the underside of the frontal lobes can grate across this uneven field of bone, causing additional damage.

But the injury does not end at the moment of impact. The event triggers a cascade of chemical and electrical activity that continues to damage the brain for days, weeks, and even months afterward. Waves of disturbance persist on the microscopic level, leading some scientists to suggest that we think of brain injury as a disease—a process that unfolds over time. I have begun to think of it this way, as expanding across time and space, silently coursing through the brain and beyond.

My mother’s green eyes, which had clenched shut upon impact, remained closed as skaters slowed around her.

Her eyes opened. She looked up at the ring of worried faces.

Rising on slippery feet, she told my father she was fine. Just dizzy, she said, as he helped her off the ice to a wooden bench where she could untie her skates. Sitting in the cold, she leaned her head forward for a moment and held it in her hands.

 

2. METHODS

Use your imagination to get your bearings: You’re in a crowded public hall in imperial Rome around the year 161 AD. Men draped in the empire’s finest fabrics mill and greet each other in voices edged with excitement. Light glints off rings and epaulets. The air is fragrant with perfumed oils and men’s sweat and something more feral—pig excrement. Heads jockey for an unobstructed view of Galen of Pergamum, the anatomist and physician who stands on a dais gesturing over an unfortunate pig lashed to a wooden board, its teat-lined belly exposed and all four legs secured with ropes cinched tight. The top of the pig’s head is pressed against the board and the flesh of its throat is exposed to the expectant crowd. The squealing is ferocious, piercing—just as Galen intended.

Galen stands in front of his audience and declares his intention to show that the voice does not originate from the heart, as commonly believed, but from the brain. Hackles rise throughout the hall. The city’s most influential politicians, scholars, and surgeons are gathered here, many of whom are Aristotelians who believe that thought, and therefore the voice, emanates from the heart. The heat of the human body, Aristotle argued, is stoked by the fire of the beating heart, whose feverish “spirits” pass through the nerves up through the neck and into the brain, where the organ’s hollow blood vessels make it the perfect cooling apparatus.

Many creatures have a brain, of course. Aristotle saw them moist and rotting with his own eyes. Octopus. Elephant. Ape. He dismantled the corpses of at least forty-nine different species and observed that the human brain is larger, in relation to body size, than the brains of animals. Holding humans apart, he did not think “other animals.” And he did not know that in the human brain the neural systems responsible for “reason” and “emotion” are as interwoven as the mythical fabric of the Fates. According to the times, the two were separate faculties, and according to Aristotle our relatively larger brains could better temper the “heat and seething” of the human heart, cooling emotion and leaving us the most rational of all creatures. In other words, the heart was the organ of the mind and the brain was a fancy utensil.

But experience has taught Galen otherwise.

When he was only twenty-eight years old, Galen was the youngest physician ever to be appointed to care for the gladiators at Pergamum. He treated men who suffered terrible wounds inflicted by sword and mace and half-starved beasts, which offered him an otherwise impossible access to the inner workings of the human body. He treated head injuries inflicted by clubs, claws, and metal spikes of all ominous shapes and sizes. He watched the wounded men recover, or not. And what he saw taught him to believe, like Hippocrates before him, that the brain, not the heart, is the organ of the mind.

Galen knows his audience is riled. Prickly and antagonistic, he delights in using public experiments to show other physicians to be fools. A well-known Aristotelian philosopher by the name of Alexander Damascenus interrupts Galen’s brazen introduction to raise the objection foremost in many minds: “But should we concede that the evidence of the senses is to be trusted?” The eyes can be deceived. The mind led astray. One should rely on the abstract logic of philosophy alone to reason one’s way to knowledge of the natural world. At issue is more than just the brain-heart debate; this is a debate about Truth, and the methods by which it might be known.

 

I have been wondering when the silence began. Maybe it started when I was trying so hard to stay quiet so she could get better.

Or maybe it came later, when I had tired of getting “I don’t know” as an answer and stopped asking questions.

Then again, maybe I didn’t ask much in the first place. Perhaps I was too shy to intrude on the adult world of illness and recovery, or too wrapped up in my own world to notice the silence stealing around me and settling into place.

 

I have been trying to remember what she was like before, testing for gradations of difference. I keep thinking about the day we went to the National Museum of Natural History, where the collection we wanted to visit was closed to the public and closed to children. I must have been nine or ten years old, but she took me looking for it anyway. There were no crowds in the basement of the museum, no children with sticky fingers pressed up against brass railings or distracted grown-ups with fanny packs and cameras searching for a sign pointing the way to the Jurassic Period, just the sound of my mother’s sandals ticking confidently through empty white corridors. I tripped along next to her in dirty white Keds, goose bumps rising along my arms every time we passed a vent blowing cool air. When we finally found the door to the National Bird Collection, a woman in wire-rimmed spectacles discreetly blocked our entrance, insisting we could not visit this particular collection. We were not scientists. Not experts. We had no business there.

My mother talked to her, warm and earnest, about how much I would enjoy it. We won’t touch anything, she promised, holding up her manicured hands with scout’s-honor palms facing out. She was a good talker, not like a used car salesman trying to be your best friend, more like your actual best friend. The skeptical guardian of the bird collection eventually agreed we could come in for one hour.

The massive warehouse was clean and quiet, divided into aisles by archival drawers like those that hold unframed paintings or blueprints. I remember feeling as though we were a million miles underground. We tried a drawer at random, and it slid open to reveal six huge parrots lying belly-up. This was almost too good to be true. I was a child of minor obsessions, and my interest in dinosaurs had recently turned, in a Darwinian way, to birds. I daydreamed over James Audubon’s field drawings and the language of avian anatomy. Pinfeather, ulna, alula. The words promised a precision I found irresistible. The parrots had been arranged in two rows of three, their green plumage brilliant against the white lining of the drawer. Six pairs of leathery feet curled up toward the ceiling, one foot of each pair tagged like evidence. The slim anklet announced the dead animal to be proof that others like it lived.

“Is there one of everything here?” I asked the woman in spectacles.

“No,” she smiled, “the collection isn’t complete.”

I couldn’t decipher the coded tags, but wondered if they recorded where the parrots came from and who had brought them here. Even now, I can’t help imagining a bearded naturalist in khaki safari gear, a machete for hacking jungle trails in one hand and a clutch of dead birds swaying from the other; men sweating in a long line behind him, balancing trunks full of tea, notebooks, and feathered bodies. It’s hard to unlearn the idea that science is about white men and their adventures. Leaning closer, I angled my head to examine the electric-blue markings around the eyes of the nearest bird. Close up, it smelled dry and slightly stale, like a library book. It rested inches from my face, within reach of my hands, so much better than the Hope Diamond upstairs.

My mother said, “If only we had a ladder . . .” and I turned to see her standing with her hands on her hips, looking up. This image remains: a tiny woman with golden curls in a sea of drawers, looking up.

Those drawers held thousands of birds, nests, eggs, and skeletons—the tiny bones linked up in patterns reminiscent of a symphony, the parts humming together into something new and irreducible. But the skulls were my favorite. I lingered over the depressions where avian eyes once rested, the bone smooth and graceful with its hollow curve and then, behind, nothing. I was mesmerized by the idea that this was the place from which the bird would have looked out at the world.

“I think she really likes this,” my mother told the woman in spectacles as we left. They were on a comfortable first-name basis by then, and we were invited back anytime the following day.

 

After she fell, my mother changed. She did not become a different person, she became different. I don’t know how else to say this.

 

Galen’s demonstration takes an unexpected turn, his response to Damascenus pitched to maximize dramatic effect: “I was mistaken in not realizing that I was coming to meet boorish skept-hicks, otherwise I should not have come.” Leaving the squealing pig untouched, he steps down from the dais and sweeps out of the hall, which has erupted in a din of discussion and disagreement. If the crowd was hungry for Galen’s performance before, it is ravenous now.

Over the next few days, he is begged to return, and when he finally steps up to the dais once more, his audience has swelled—his is now the hottest show in all of Rome. A pig lies lashed to the board, as before. This time, Galen slices through the tough skin of the pig’s throat, laying bare the thorax. He fishes in the bloody riot of exposed flesh for the pig’s intercostal nerves, which are known to be connected to the brain—not the heart—and which we now know include the laryngeal nerves. Finding what he wants, Galen deftly loops threads around the slippery strands. Leaving the threads loose, he strikes the animal to make it cry out.

Perhaps Galen lingers a moment and lets his audience listen to the pig’s shrieking porcine voice. Then he tightens the threads around the exposed nerves and strikes the animal again. This time, though the pig flinches and struggles, there is no sound. One can almost see startled observers raise hands to throats. The crowd marvels at the silence.

They marvel yet again when Galen unties the threads, strikes the animal a third time, and produces a resounding squeal. The voice, if beholden to these nerves, must be beholden to the brain. This is the first time an experiment has shown a causal relationship between brain and behavior. What a miracle to                       suddenly see a fact of physiology with such clarity—the mystery of the voice made, by one deft twitch of the surgeon’s hand, less mysterious.

Galen’s demonstration with the squealing pig marks the dawn of experimental brain science and his legacy will stretch across centuries, continents, and cultures. His most influential work, De usu partium corporis humani, will define the practice of Western medicine for fifteen centuries, well into the European Renaissance, but perhaps his most significant achievement was to unite the logic of philosophy with experimental observations of the natural world. This union paved the way for the scientific method, that elegant equation of theory, experiment, and data now inscribed on the very heart of modern science.

 

Ask a question. Form a hypothesis. Test it. Make conclusions based on evidence. This logic is repeated in every scientific paper published today, in which you will also find a “methods” section, where the researchers describe, sometimes in numbing detail, exactly how they did the experiments that gave them the data that led to their conclusions. But how can someone who is not a scientist, who does not have the controlled setting of a lab and the precision of finely tuned instruments, come to any sort of reliable knowledge about the world through which she moves?

 

To say that my mother became “different” does not satisfy. There is always more than one way to say a thing, and language is always privately polyvalent—I say “red” and you see a color and also apples and anger and the swish of a matador’s cape, the ribbon tied around a gift given by a man you loved and never saw again, which reminds you that sea horses mate for life. You know, “red.” So let me try again.

After she slipped on that frozen lake in Yosemite National Park, my mother became quiet and tender, sensitive to the world in unexpected ways. I remember riding in the back seat as my father drove us home to the California coast a few days later, leaning my temple against cold glass and watching her hand grip the passenger door handle. She gripped the door handle, her whole body tensed against the back-and-forth of the car. As the trees thinned out along the dizzying route of switchbacks that ribbon across the Sierra Nevada, the car wound to higher altitudes and she said my father’s driving was making her nauseous. He slowed and tried to take the turns more gently, but still she felt queasy. This was not like her. Usually I was the one to get carsick. When we arrived home, just north of San Francisco, she complained of dizziness and exhaustion and disappeared into her bedroom. I think I’m falling back, here, on the conditional language of the medical literature—“the patient complains of”—as if the facts of her particular suffering have yet to be established. I will try to do better.

A few days later, my older sister flew home from college for the winter holidays and we slept stacked in the bunk beds we’d shared until she left. Our parents stayed up late on Christmas Eve, arranging presents even though we were far too old to believe in Santa Claus. My mother crafted bows out of ribbons lovingly recycled year to year, then made sure all the packages were visible from the living room doorway, where we gathered in the morning and waited until everyone was ready before anyone could take a step into Christmas Day. We spent the whole day in our pajamas, opening one gift at a time, meals forgotten in the wake of hot chocolate and leftover pumpkin pie. In the evening, my father cooked a turkey and we made the obligatory visit to church, where my sister and I knelt close, poking each other and jostling elbows across wooden pew backs. But that year, my mother suffered from headaches, dizziness, and fatigue. She seemed sensitive to light and sound, and she spent long hours in the bedroom with the blinds pulled and the door closed. Eventually she would emerge, rejuvenated. She would laugh and eat pie. After a few hours she would retreat to the bedroom again, looking pale and confused. The holiday cards, which she usually opened with such fanfare, sat piled in bright stacks on the hall table.

“I’m tired,” she said.

“She just needs to rest,” my father said.

In those first few weeks, I didn’t feel alarm, or even great interest. I wanted her to feel better the same way you want someone to feel better when they have the flu.

It must have been January before I noticed that the changes in my mother’s behavior didn’t seem to be going away. She forgot appointments, her wallet, to put mascara on one eye. Her speech had slowed down, her voice crawling over elongated vowels as if she were speaking underwater. Words escaped her, the things she wanted to say just out of reach. My purse. Stuck. Blooming. She would put a hand to her forehead and sigh, heavily, as if what was being asked of her was simply too much. I got into the habit of guessing what she wanted to say, finishing her stalled sentences, often incorrectly, just to help them end.

I remember slipping quietly into my parents’ bedroom one afternoon while she was resting—there must have been a reason, a permission slip to be signed or a message to deliver, because when that door was closed it was not to be opened. Sunlight seeped through the white curtains and cut a pale rectangle across the foot of the bed. I don’t remember what I said, but I can still see how she shut her eyes when I spoke. She pinched up her forehead as if I were hurling words into her face and she had to duck to avoid getting hurt. When they weren’t closed, her eyes ran across her bedside table and her blankets, flitting from alarm clock to bedposts to my face to the wall beyond like a pair of restless birds looking for a place to land. It scared me.

She was a ship taking water, the currents changed and changing, the wind no longer at her back. She was routinely exhausted by the pace of daily life, her mind unable to keep up with demands it once met so flawlessly.

But then, she had good days. On good days my mother was lucid and charming, just like her old self. Once, she packed a beer in my school lunch, but most afternoons, when I opened my brown bag in the concrete middle school courtyard, I would find a sandwich and a drink as normal as those my classmates pulled from theirs. Or at least as normal as could be expected from a household where chips, candy, and soda were forbidden. My parents leaned, though not as far as some California transplants, towards the hippie side of the cultural spectrum. At least one piece of furniture was upholstered in striped velour, and I distinctly remember a macramé lamp. On good days, my mother whirled around us as she always had, and my fear was lifted and forgotten in her wake.

This backsliding scale of wellness confused the whole family. She seemed fine one day, addled the next. So was she sick, or not? As a child, I didn’t understand what was happening to her, but I assumed whatever was wrong was an adult problem that would have adult solutions. I figured they were handling it.

“Be quiet, your mom’s resting.”

But not getting better.

 

There is much I don’t remember, but much I never knew to begin with. In the same way a body doubles over in response to a punch in the gut, our lives contracted around my mother’s injury, curling over to hide and protect it. We didn’t talk about what was happening to her, or to us. Silence became habit, and it’s only as an adult that I’ve begun to see the damage it can do.

By the time I left home for college the silence had become so routine as to be indistinguishable from the noise of daily life. Eventually I turned to the Internet, where I found hundreds of websites riddled with unfamiliar terms like closed head injury, post-concussive syndrome, and traumatic brain injury. There were acronyms—LOC, PCS, TBI—and jargon—lesion, sequelae—written in a language I didn’t speak. Did my mother have a “concussion” or a “traumatic brain injury”? What was the difference? I had no idea. This was before TBI had become a household term because of stories told by professional athletes and veterans of the wars in Iraq and Afghanistan. At the time, I had never heard of TBI.

Though overwhelming, the Internet provided a few basic facts. It’s a common misconception that “head injury” and “brain injury” refer to the same thing. Head injury: any injury to the head, including broken cheekbones and a lacerated scalp. Brain injury: any injury that affects the brain itself, sometimes with no external injury to the head. The latter includes everything from shaken baby syndrome to blast injuries to a bullet lodged in the brain. (It took me an embarrassingly long while to figure out that “acquired brain injury” simply means damage that occurs after birth, as in acquired vs. congenital.) These terms are often confused in the scientific literature, adding to uncertainty about the prevalence of brain injury and fueling debates about diagnosis and treatment. Confusion reigned at every level, from how to diagnose the severity of an injury to what might be the most effective treatments. From the outside looking in, the field of brain injury research seemed to be a bit of a mess.

Or maybe I was looking in the wrong place. I needed a field guide, so I ordered a slim green paperback with the promising title Head Injury: The Facts. It was simple and forthright. It promised answers.

The first few paragraphs are written in a reassuring, expert tone: “Until recently the psychological ramifications of head trauma had been largely overlooked, and they were therefore unknown to almost everybody including the patient and the people close to them.” This sounded familiar. “Most people suffering a residual compromise of mental efficiency following an accident with minimal or no loss of consciousness attributed their problems to psychological causes: their physicians often dismissed these patients as neurotics, compensation seekers, or both.” This was getting uncomfortable. I had sometimes wondered whether my mother’s problems weren’t more psychological than physical. I thought of those categories as somehow separable. It was hard to imagine that such a seemingly minor fall could leave such a bizarre constellation of symptoms in its wake. But my feeling of concern was warped over time by frustration that she wasn’t getting better, as if this were a test she was somehow failing. It didn’t occur to me that lack of empathy might be a failure of imagination.

The book goes on to suggest that people with cognitive and psychological problems resulting from a brain injury not accompanied by any obvious physical injuries are likely to have those problems overlooked: “Only patients with obvious crippling or other physical alteration were likely to have the permanent neuropsychological residuals of their brain injuries recognized, although even then higher mental functions were either ignored or misinterpreted.”

The Oxford English Dictionary defines neuropsychological as “the study of the relationship between behavior, emotion, and cognition on the one hand, and brain function on the other.” My mother certainly seemed to think and act more slowly, to “suffer a residual compromise of mental efficiency,” but she wasn’t an invalid. She didn’t need a wheelchair or a cane or help washing and dressing and eating. She didn’t need nurses and trays of sterile white plastic—the care an institution can provide. But she was not well. This left her, according to these authors, in a group that was not “likely to have the permanent neuropsychological residuals [of the injury] recognized.” She was someone whose difficulties with “higher mental functions” like memory and attention were both “ignored and misinterpreted” by those around her. By me, at the very least.

The last paragraph on the first page stopped me cold. That page is now marked in faded green highlighter and has been read so many times the book’s binding has begun to crack. This paragraph articulated my experience so clearly I couldn’t believe the words were written by someone who didn’t know my family:

 

As the misdiagnosed patients have suffered from neglect, bewilderment, and despair, families lacking knowledge about their head-injured patient have suffered too. Many families have gone through a progression of torments that begins with puzzlement and then confusion as the patient no longer responds in familiar and appropriate ways. Frustration and anxiety arise as the uninformed family members discover that their efforts are ineffective, and may even make the situation worse. Many family members feel shame and guilt at what they believe are their failures to cope with the patient’s problem behaviors. Depression is almost inevitable. Disruption of once solid family relationships is not an infrequent occurrence, which further compounds their misery.

 

“Misery” seemed a bit melodramatic, but basically this book had us nailed. I’d always thought that no one, not even her doctors, knew what was wrong with her. I’d always reasoned this was why we ignored her behavior, for the most part, and waited for her to get better, as if it were something she was doing, and had to do, on her own. But someone knew. These authors, certainly. Our silence and inaction were not, in fact, a mystery, and my family was just one among many.

 

When I finally asked my mother if she would talk with me about her brain injury, I was home for the holidays and we were passing each other in the downstairs hallway of the house where I grew up. Her arms were full of folded sheets.

She paused and said, “I’ll think about it.”

For the next three days, we pretended this conversation had not taken place. We shared meals, walked my parents’ dogs, went to a movie, and the subject very purposefully did not arise.

On the third day she said, “Do you know you’re the only one in the family who’s asked me about this in fifteen years?” She said it quietly, without anger or reproach, but it broke my heart.

 

Method, from the Greek methodos: pursuit of knowledge.

 

At first, I wanted to know which areas of my mother’s brain were damaged and how that damage could explain how she changed. I assumed that what I learned could be organized into neat columns in my notebook: brain area, function, deficit. This seemed like an achievable task—a logical road of inquiry. At the end would lie the answers, facts to be picked up and held in my hand like pebbles, each one hard and round and certain, ready to be placed safely in my pocket as I turned to head for home.

Meehan Crist is writer-in-residence in Biological Sciences at Columbia University. Previously, she was an editor at Nautilus and The Believer.