Authors: Molly Birnbaum
But, he added, “that doesn’t mean it’s not providing information—it is. It’s providing information about the individual, and that information may influence how an individual interacts socially with another.”
The best example of MHC’s influence comes from what is known as the “sweaty T-shirt study, ” by Swiss scientist Claus Wedekind in 1995. In this study, Wedekind had 44 male students from the University of Bern wear the same 100 percent untreated cotton T-shirt for two nights straight. It was a Sunday and a Monday night, and during the day, they kept the shirts in open plastic bags. The participants were given odorless soaps and detergent to clean themselves and their sheets. They were told to avoid heavily scented foods and activities. On Tuesday, Wedekind then had 49 female students smell the sample shirts. The women rated the shirts based on pleasantness, using odor alone. All of the participants—men and women—had previously been tested for their MHC type. What Wedekind found was fascinating: the women were most drawn to the T-shirts of men whose MHCs were genetically different from their own.
Evolutionarily, this makes sense. If odor preference is influenced by the genetics of MHC and plays a role in selecting a mate, then two parents with different MHC types would make a baby with a stronger immune system. Similarly, being drawn to someone with a different smell and therefore genetically different immune system would help to avoid inbreeding.
Interestingly, Wedekind also found that women who were on oral contraceptives were
not
drawn to men with different odor prints. In fact, he found that the opposite. “This indicates that steroids which are naturally released during pregnancy could change body odour preferences, leading to a preference for odours which are similar to those of relatives,” he wrote in the paper “MHC-Dependent Mate Preferences in Humans.” After all, evolutionarily, again, it would make sense for pregnant women to desire to be close to kin, for protection and care. Taking it one step further, Wysocki and colleagues found, in 2005, that body odor preference is influenced not only by kin, but by gender and even sexual orientation.
This scent preference isn’t always conscious. There are areas of the brain at work in ways we can hardly know. In 2008, Johan Lundstrom and colleagues tested the brain activity of 15 healthy women when smelling samples of body odor belonging to strangers and friends, and then a synthetic material that had been made to have an almost identical scent. His results were wild: though these women could not tell the difference between the real and fake body odors by their nose alone, Lundstrom found, using PET scans, that they processed each type of scent in different parts of their brain. The true body odors activated areas of the brain known to deal in emotional stimuli and attentional efforts, whereas the synthetic used a region for high-odor processing, like labels. Somehow, somewhere, their bodies knew how to distinguish real and imposter human scent—potently, emotionally, importantly.
So,
I thought, as I sat there speaking with Wysocki,
smell is a way of relating to people.
I knew this: I’ve talked with women who say that they can tell on a first date that they like or dislike their companion by their smell.
But I couldn’t help but think: What about me? It was easy to ignore the possibilities of pheromones when the concept itself is so riddled with the unknown. But this? This was just smell. Without the ability to smell, I
did
lose something more than the smell of bread baking in the oven. I lost something that had nothing to do with the existence, or not, of the vomeronasal organ, of scentless chemicals flying through the air. I lost a way of relating, of understanding, of processing my world.
“Without a sense of smell, then,” I asked Wysocki, “I would not react?”
He paused a moment.
“Yes,” he said. “That would be my prediction.”
AS THE SUMMER
heat grew and then faded into the burnished reds of fall, I pushed my relationship doubts aside. I didn’t want to admit that something was wrong. But I wouldn’t have to, I thought. After all, exciting things were afoot. The auras of scent hovering in the periphery of my perception had begun to crystallize, sticking me one by one with pinpricks of scent. Real, clear scent. I woke up each morning tingling with hope, with expectation, with the immediacy of this change.
I smelled cucumbers one day while chopping for a salad on the counter in my apartment. They smelled wet, cold, and slightly sweet, like wavy lines of a pastel green shimmering behind my eyelids. I yelled to my roommate who sat on the couch nearby: “Cucumbers, Jon! CUCUMBERS!”
He looked up. Concerned. “Are you okay?”
“I can smell cucumbers,” I said, quietly this time, as I waved the vegetable back and forth under my nose like a wand.
Suddenly, I could smell the chocolate from a pack of M&Ms someone was eating on the subway several seats away. I stared at them, goggle-eyed, for two stops straight. I couldn’t believe the strength, the depth, of the scent and I fixed my gaze until the eater had finished, crumpled up the crinkled yellow wrapper, and walked away. One afternoon, a few weeks later, a whiff of perfume on Madison Avenue and Seventieth Street—smelling of grace, of wealth—stopped me in my tracks. Cilantro, the leafy green herb that I chopped to add to another salad, came on an evening in late June, pungent and cool and begging for guacamole. The jasmine of my morning tea arrived on an exhale; cantaloupe’s summer-fresh sweet suddenly beckoned from five feet away. The spice of a man’s deodorant—quickly, vividly Alex—appeared on the subway on a morning in July.
Slowly, painstakingly, almost secretively, individual smells had begun to return. They arrived alone, just like the rosemary and the chocolate of those months before. They arrived one at a time, confusing me with a combination of familiar and strange. Each scent brought color to my landscape. Each scent brought joy.
Not everything was returning, though. Like the sharp light of a streetlamp on an otherwise deserted street at midnight, these smells arrived singularly, spread apart, and glowing like mad. I could go days without smelling a thing and then—
pop!
—the scent of laundry or butter or soap would infiltrate my nose. I couldn’t believe it. Against all the odds, I seemed to be recovering. I wanted to scream it out to my fellow riders crunched by my side on the subway. I wanted to hurl it at the ENT who had left me feeling so alone.
Look,
I wanted to say.
Cucumbers!
Their once common, negligible scent had returned—intoxicating, almost ambrosial. The scent of melon could bring me to tears.
And as these scents crept back, New York City, which had been a blank smellscape upon my arrival, began to pulse with new layers of meaning. The park carried a twang of smoke, whiffs of tree and flower, the murky metallic ooze of a water fountain, drifting coal and grill, roasted nuts. The streets were filled with surprises—hot dogs! coffee beans!—and the taxicabs called to me with their old leather, new cigarettes, and remnants of
Chanel No. 5,
the signature powdery aldehyde of whomever just held my seat. A walk through Chinatown brought whiffs of salty leather handbags, raw fish on ice, deep-fried balls of sweet dough served in paper cones, and the faint trails of both orange rind and urine. My apartment came with lemony dishwasher detergent, damp cardboard, the deep green of basil. These smells reappeared quickly, raucously, reminding me of what had been gone: the shimmering cloud of garlic in the apartment of friends, the cold but floral aroma of a department store, like a skating rink just ironed smooth. Instead of retreating into my mind as I walked around the sidewalks near work, dodging tourists and businessmen with a practiced tunnel vision, I found myself often tugged out of my mind and into the world around me with the unexpected scents—some familiar, some not, but always in that moment, right there. I noticed more. I concentrated harder.
I went back to the Strand, which I had avoided since my blank trip back in March, and stood deep within the shelves of used books. I smelled them: cautiously, carefully, desperate for more. When I opened a stiff old book in the New York Public Library on an evening that August, its mildewed pungency sent shivers down my spine. Shopping at the farmers’ market in Grand Army Plaza on a Saturday in September, I could recognize the spicy aroma of hot mulled cider from down the block. Autumn, I found, once again held the scent of roasted pumpkin seeds. Suddenly, the homeless man who cleared the subway car with his stench contained more sadness than simply dirt and grime.
On a Sunday morning, I went for a walk with Jon along Seventh Avenue. Suddenly, there was a smell, strong and slightly sweet, a memory just out of reach.
“What is that?” I asked, inhaling deeply and looking around.
“What is what?” he asked, confused.
“That smell,” I said.
“Oh.” He pointed to the next block, where a line was snaking outside La Bagel Delight, a crowded store I had often walked past but never entered.
“Bagels,” he said. “Fresh baked. It always smells like that.”
It made sense: the warm, hearty scent combined yeast and sesame and, perhaps, early weekend breakfasts at my grandparents’ house upstate. For the first time in more than a year, I understood why a line formed out the door so early on Sunday mornings.
THE OLFACTORY NEURONS
are wily little things. They are tiny and delicate in their threadlike path from the nose to the brain, easily severed and subject to chance. But they have pluck; they’re bold. The olfactory neurons are capable of tremendous growth. They can rise from the dead. And mine, it seemed, were on the move.
In the accident my olfactory neurons, which wind from the upper quadrant of the nasal pathway through the cribiform plate to the brain, were most likely severed with the impact of the crash. When I lay on a cot in the hospital in those following days, going in and out of CT scans and talking gibberish to my mother, the remains of my truncated olfactory neurons receded. And then they died. For most of the neurons in the human body, that would be the end. But not in the nose.
The olfactory stem cells replenish constantly even in a healthy nose. They are some of the only neurons in the human body with the ability to regenerate from scratch. And they do so constantly, growing like the perennial flowers in my mother’s garden but on warp speed. The olfactory neurons in rats, it’s been shown, are completely new every thirty to sixty days. The rate in humans, many scientists believe, is slower, though no one is yet sure by how much.
As smells began to return, I felt supplanted into an alternate reality, one where the sensory world changed shapes, flowing like liquid before my eyes. I felt subsumed by the supernatural and crushed by my wild luck. It was only later, though, that I began to wonder what, exactly, was happening in my nose. The olfactory neurons are some of the only neurons in the human body capable of being replaced. Why?
I called Donald Leopold, a busy doctor at the University of Nebraska Medical Center who works with disorders of smell, to find out. He spoke to me breathlessly as he walked from one meeting to another, quickly throwing facts into the phone like tennis balls.
It is possible that the olfactory neurons die and regrow because they are exposed so intensely to the environment, he explained. These are the only cranial nerve cells that actually make contact with physical stimulus directly from the outer world, interacting directly with odor molecules on each inhale. They aren’t in the possession of that buffer of skin. “The neurons wear down; they become fatigued,” Leopold said. “We know that the sense of smell is active in metabolizing pollutants and dangerous things that you smell. It’s still just speculation, but maybe they are built to turn over because they are just doing a lot of dirty work. They regrow to protect you.”
They do more than that,
I thought. This ability—the intricate, innate program of growth—gives people like me the ability to recover. It is possible for the neurons to regenerate after a head injury. Or after the damage of a virus, or the complications of a surgery for that matter. After all, they’ve done it millions of times before.
On one of my many trips to the Monell Chemical Senses Center I sat at a table across from Beverly Cowart, who headed the Monell-Jefferson Taste and Smell Clinic. I asked her about the regrowth. Is it possible for all anosmics to recover?
Yes, she said, simply. It is. And then she paused. For almost a minute Cowart, a woman who appeared constantly on the verge of speech, sat silently. I waited.
“The striking thing about it is how long it can take,” she continued. “I usually look at a two-year window. If you’re not getting something back by then, though, I would advise you that it’s very unlikely to come back at all.”
“If I’ve gotten something back, even if it’s just a little bit, does that mean the rest will return as well?” I held my breath. With the barrage of new scents during those months in New York, I had assumed that my full recovery was imminent. If I could smell some things, why not all things? My mind had whirled with possibility: maybe I could still become a chef.
“No,” Cowart said. She explained that there are many obstacles for the damaged neurons in the brain. I watched as she counted them on her fingers. First, there must not be too much scar tissue clogging up the Swiss cheese holes of the cribiform plate as the neurons begin their path back toward the brain. Next, if they get that far, the neurons must effectively reconnect to the olfactory bulb. And finally, the bulb must be healthy enough to sustain neural growth, allowing neural input to reach higher brain centers, where smell is actually perceived. In loss due to head injury, there is always the possibility that there was more central damage to the brain. It’s impossible to predict, on this road paved with obstacles. And Cowart has seen it all—from absolutely no return to just a small seepage of scent slowly crawling back into perception, to a swath of recovered smells so wide that the patient can no longer recall what’s missing.