Last winter, Andreas Keller, a dedicated neuroscientist, took a bold step toward his dream by launching an innovative art gallery. This isn’t just any gallery; it’s the nation’s first commercial venue dedicated entirely to the fascinating world of smell-based art. He transformed a deserted barbershop in New York City’s vibrant Chinatown into this unique space and collaborated with artist M Dougherty for his inaugural exhibition in February of 2021. A standout feature was a drilled hole in the exterior wall that allowed the delightful aroma of a pine-scented perfume named “Forest Bath” to waft out to the street, creating a captivating olfactory experience that blended with the smells of steamed dumplings, nearby dumpsters, and the aromatic offerings burned by his Chinese neighbors to honor their ancestors.

“The gallery had always been a fantasy, but the pandemic brought it into focus,” reflects Keller, comfortably seated in his AstroTurf-carpeted office, which he plans to enhance with a molecule that emits the scent of fresh-cut grass. The lockdowns provided the contemplative hours he needed to detach from his regular work, igniting the realization that there might finally be a market for his visionary concept, especially as loss of smell emerged as a notable symptom of early Covid-19 cases.

The sense of olfaction has long been considered the underdog among our senses. It possesses a blend of primitive and intricate qualities, making it challenging to study, especially in our increasingly digital world. Our scientific comprehension of how smell operates lags significantly behind our understanding of hearing and vision. Currently, the nuances of smell cannot be recorded, shared through email, or showcased on platforms like Instagram. A 2011 survey revealed that over half of young adults would rather lose their sense of smell than their smartphones, highlighting the diminished regard for this essential sensory experience.

However, the arrival of the coronavirus sparked a renewed interest in olfaction. Individuals suffering from the loss of smell realized the dangers of being unable to detect smoke from fires threatening their homes, or the scent of their loved ones, which some reports suggest has led to marital issues. They also discovered that many flavors, such as that of chocolate, are deeply intertwined with our sense of smell. “You don’t know what you have until it’s gone,” Keller poignantly states.

For those fortunate enough to retain their sense of smell, the experience of living in a world muted by face masks or limited to sanitized Zoom calls heightened the collective yearning to deeply engage with the aromatic world once again. This phenomenon likely accounts for the recent explosion in the perfume and home fragrance market, drawing curious visitors into Olfactory Art Keller, the gallery dedicated to this multi-sensory exploration.

“When you are asked to smell art,” Keller explains, “you realize how impoverished your perception of the world is when you limit yourself to just the visual aspect.”

For several weeks, the gallery’s windows were covered in tin foil to facilitate an immersive experience where visitors could distinguish between the aromas of “old banana” and “young banana,” a playful nod to a classic Velvet Underground album cover. Guests could also experience a perfumer’s interpretation of what a beaver might smell like to a dog, perhaps reminiscent of marzipan, or encounter the unique scent of George Washington’s false teeth. During my visit, I was instructed to engage with a rainforest landscape presented as a giant scratch-and-sniff sticker, which released a refreshing burst of microencapsulated citrus, reminiscent of the fresh breath of the jungle.

“Some visitors find it very confusing,” Keller admits. Those who are typically adventurous in galleries might retreat to the street, perplexed by the experience. “There are always those who can’t detect any scent at all and assume it’s some kind of prank.” During the banana-themed exhibit, several people with a strong aversion to bananas surfaced, revealing an inexplicable dislike for the fruity aroma. Keller humorously notes, “I know one such person who refuses to sit at a table with someone eating a banana and even declined to attend that exhibition.” Yet, those visitors willing to engage with the scent titled “Sinner” often find themselves debating what they are perceiving—could it be antiseptic, church incense, or perhaps the rich aroma of tandoori chicken?

These varied personal interpretations are precisely what Keller has devoted a significant portion of his academic research to exploring: understanding the reasons why different individuals perceive and interpret identical odors in distinct ways—or sometimes, fail to notice them altogether. These inquiries delve into the complexities of how our brains encode odors and how we achieve our unique perceptions of smells. For instance, how does a combination of proteins and carbohydrates lead to our recognition of the delightful scent of freshly baked sourdough, which became a household favorite during the pandemic?

With the recent surge in interest and funding in the field of olfaction, scientists are hopeful for advancements in our understanding of this often-overlooked sense. The future may bring not only the growth of aromatic art spaces like Keller’s gallery but also the potential revival of technologies such as Smell-O-Vision, the recently discontinued oPhone, and scent-based strategies to diagnose conditions like Parkinson’s disease and aid in treating post-traumatic stress disorder. We may even see the rise of perfumed dating applications and virtual shopping experiences that can identify the ripest avocado from a distance.

Moreover, many Covid-19 survivors continue to face lingering olfactory issues. These individuals are understandably frustrated with the prevailing belief that if a sense of smell is lost for six months, it is likely gone for good. They are now advocating for enhanced clinical approaches to address these challenges. “The amount of research has just increased exponentially,” states Richard Doty, director of the University of Pennsylvania’s Smell and Taste Center. “This is a significant area of interest. However, the complexities of this sensory system make it a challenging field to navigate. I don’t expect we will have all the answers overnight.”

Advancements in this domain may well rely on unconventional creativity and interdisciplinary collaborations among perfumers, linguists, artists, engineers, and possibly even anthropologists and foraging communities that have never encountered certain scents, such as vanilla or Camembert cheese. Keller recently earned a PhD in philosophy, which he believes complements his previous PhD in genetics. “Perception is both a philosophical and scientific challenge,” he explains. The elusive truth about smell seems to emerge unexpectedly, only to retreat, much like the fleeting aromas of lilacs carried away by a gentle June breeze or the remnants of yesterday’s stir-fry.

Why do we struggle to comprehend the intricacies of our sense of smell? Unlike color vision, which was thoroughly understood in the 19th century when scientists identified that a spectrum of colors arises from just three types of receptors in human retinas, olfaction is far more complex. The human nose contains approximately 400 receptor types, as established by Richard Axel and Linda Buck, who were awarded the Nobel Prize in Physiology or Medicine in 2004 for their groundbreaking work. These receptors sit on specialized neurons that transmit information deep into the brain, specifically to one of the two olfactory bulbs, where odors are processed. Yet, we are still far from grasping which specific odors each of these receptors recognizes, much less how they work together in harmony.

If vision is the primary sense for humans, why do we possess such a vast array of olfactory receptors? “It seems excessive, doesn’t it?” a researcher remarked. Light is a form of electromagnetic radiation, and the three color vision receptors can combine to process a wide spectrum of wavelengths. In contrast, smells are not linear wavelengths but rather a complex amalgamation of chemical particles floating in the air. Our bodies have evolved to develop receptors capable of recognizing a multitude of molecules that are volatile enough to enter our nostrils, necessitating a diverse receptor arsenal.

Take the notorious banana aroma, for instance; it is composed of approximately twenty distinct molecules, each designed for overlapping sets of receptors. This causes some receptors to activate while others might be inhibited, generating the harmonious scent we associate with bananas. In a 2014 paper published in Science, Keller and his colleagues estimated that humans can differentiate at least a trillion unique smells present on our planet. Complicating the scenario further, our numerous odorant receptors possess various variants, some of which are less sensitive or entirely nonfunctional in large segments of the population.

To launch his olfactory studies, Keller created mutant fruit flies by manipulating their olfactory receptors. However, he soon realized that the diverse population of New Yorkers offered a more intriguing subject pool, as they hailed from various corners of the globe. He recruited participants through platforms like Craigslist, administering a series of smell tests to hundreds of individuals while collecting saliva samples for genetic sequencing. His goal was to link specific anosmias—the medical term for singular smell deficits—to the corresponding receptors responsible for processing those smells, thereby mapping out the functions of the approximately 400 receptors and uncovering why individuals perceive or favor certain scents. “Once you identify individuals with nonfunctional variants,” Keller elaborates, “you can analyze the significance of that gene for humans.”

The takeaway is that approximately 30 percent of your receptor functionality may differ from that of your neighbor, which explains why conversations beginning with “Do you smell that?” frequently devolve into confusion. For example, a molecule called androsterone—a musk found in human sweat and truffles—can evoke scents ranging from sandalwood to urine, or even be completely undetectable, depending on the individual. Previously, researchers believed that the phenomenon of “asparagus pee” was not universal because only certain individuals reported experiencing the distinctive odor after consuming asparagus. In reality, only some noses can detect it, but for those who can, the scent is universally acknowledged—a fact that became evident when those individuals compared their experiences with one another. Even professional perfumers sometimes require assistance to accurately gauge the scent of a particular ingredient, such as cinnamon.

In addition to the myriad functional odorant receptors, there exist around 600 additional olfactory “pseudogenes” that, to current scientific knowledge, do not code for active receptors in any living individual. Some researchers interpret this cluster of dormant DNA as evidence of the decline of the human sense of smell. It is possible that our olfactory abilities have diminished as our methods of mate selection have shifted, emphasizing traits other than scent. Such evolutionary atrophy is not uncommon; for instance, bottlenose dolphins and other toothed whales have seemingly lost their sense of smell, likely to allocate more brain space for echolocation.

Yet, other theories exist. Given the multitude of scents in our environment, a deficit in a single receptor type is seldom detrimental, which may lessen the evolutionary pressure on these genes. (Although, try explaining that to the 20 percent of the population that cannot detect the bitter-almond aroma of cyanide.)

While there is certainly variability among the other senses, it is noteworthy that nearly everyone is “noseblind” to some scent or another, often multiple scents, whether it be freesia, wet basements, or cilantro. Specific anosmias can be more pronounced than deficits in our other senses. For instance, a colorblind individual may insist that grass appears red instead of green, while someone who is noseblind might not perceive the existence of grass at all. (This is where that philosophy degree of Keller’s might prove useful.)

To illustrate this further, an individual with a less-sensitive variant of the odorant receptor OR2J3, which is linked to the detection of low concentrations of cis-3-Hexen-1-ol—an aromatic molecule that imparts a grassy scent—might remain oblivious when Keller finally gets around to perfuming his AstroTurf.

To delve deeper into my own olfactory perception, I visited the Monell Chemical Senses Center in Philadelphia, home to Joel Mainland, a prominent figure in the field and a frequent collaborator of Keller’s, at least until the allure of the downtown art scene tempted him away. While Mainland has yet to establish his own avant-garde gallery, his lab exemplifies the fascinating intersection of art and science. He recounted a graduate school experiment that felt more like experimental theater: blindfolded and equipped with headphones, he was instructed to follow a scent through the grass of a public park. The results revealed that humans could indeed track scents, albeit not nearly as effectively as dogs. When the same experiment was conducted with a duck carcass, two actual dogs in the park raced past the slower human participants, proving their superiority in scent detection.

Currently, Mainland’s toolkit includes sleep apnea masks and a fake plastic nose resembling a prop from a Groucho Marx sketch, repurposed from a device known as the Nasal Ranger, originally designed to help humans track offensive and potentially hazardous odors. Mainland has adapted these tools to deliver specific odors in reliable quantities to human subjects, a challenging endeavor. While vision scientists can easily procure color monitors from major retailers to display desired colors and images for global sharing, there is no efficient method for communicating smells without being physically present in the same environment. “Unfortunately, odors cannot yet be stored electronically, and they continuously dissipate, which can be quite discouraging,” Mainland expressed. Capturing and preserving them is an art form in itself. To evoke a “smoky” essence, lab members often warm cotton balls infused with a specific scent, storing them in airtight containers for use as training aids for study volunteers. A jar labeled “Animal” contains collected horse sweat. While Mainland doesn’t aim to bottle lightning, he still needs to encapsulate the elusive “Ozone” scent, reminiscent of the fresh aroma following an electrical storm. I strategically avoided inquiring about the jar marked “Fecal,” but I was aware that other labs stock a synthetic compound known as “U.S. Government Standard Bathroom Malodor,” based on real military latrines, colloquially dubbed “Stench Soup.”

Mainland carefully decanted some liquid samples for me, demonstrating the meticulous nature of his work. Like many in his field, he has harrowing stories of lab accidents that can pollute the air for days. (Mainland once mishandled a vial of grapefruit mercaptan, which emits an odor reminiscent of sulfur mixed with fruit snacks, while Keller had a similar mishap with popcorn-like diacetyl.)

Almost immediately, I detected a smoky sausage aroma: guaiacol, which some individuals find overwhelming and unpleasant, but it merely made me feel hungry.

Next, we transitioned to testing various musks. One sample had a powdery sweetness reminiscent of Necco Wafers, but I struggled to identify others, performing rather poorly in comparison to a bottlenose dolphin’s olfactory prowess.

“Try this one,” Mainland suggested, uncorking another sample.

“I have no clue,” I stammered after several deep inhalations of what seemed odorless. “Plant water? Dog breath?”

He shot me a knowing look. “It’s possible that you simply cannot detect musks.”

Then again, it’s also feasible that some of these samples had degraded past their effective scents. Without genetic analysis, we may never know, as Mainland has previously established that he cannot perceive certain substances himself. It could be a classic instance of the noseblind leading the noseblind.

Just weeks prior to my visit, Mainland’s lab, along with Keller and other co-authors, published a paper exploring the genetics of musk sensitivity. This work received partial funding from the beauty and personal care company Unilever. The global fragrance industry is captivated by the idea that understanding the genetics of smell could help them attract previously disinterested consumers. “Numerous companies approached us,” Mainland recounted, “expressing their challenges in creating fragrances that appeal to the Asian market. They inquired if our research could guide them in determining which scents would resonate with that demographic based on their olfactory receptors.”

To investigate this, the researchers surveyed 1,000 Han Chinese individuals, asking them to assess a selection of common odors. They then compared these findings with data from hundreds of ethnically diverse New Yorkers who had previously undergone smell testing and genetic sequencing. The results revealed differing reactions to two specific substances. One was a molecule naturally occurring in human armpits, a potent and undesirable component of body odor (which deodorant manufacturers strive to mask). The other was Galaxolide, a woody-scented artificial musk widely used in soaps and kitty litter (although its scent profile to cats remains elusive).

The contrasting responses to these two chemicals correlated with genetic variations among individuals regarding two specific odorant receptors, marking the first instance of scientists linking genetic differences to olfactory perception.

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