Christina Kim

The odor molecules move up and up, lightning fast.

The odor molecules move up and up, lightning fast.

The genes responsible for those receptors are what Linda Buck discovered in 1991. They detect the chemicals, then start communicating with other neurons that will carry that information to a part of the brain that processes scent. And that's the amygdala hippocampal complex.

The genes responsible for those receptors are what Linda Buck discovered in 1991. They detect the chemicals, then start communicating with other neurons that will carry that information to a part of the brain that processes scent. And that's the amygdala hippocampal complex.

This also happens to be the part of the brain where our emotions and memories are processed.

This also happens to be the part of the brain where our emotions and memories are processed.

Ever since I was a little girl, I've been enveloped by the smell of lemon, rosemary, and spices. It's the smell of this Spanish perfume called Álvarez Gómez Agua de Colonia, the classic fragrance that's been made in Spain since 1912, that my grandmother, mi yaya, and my mother have always worn.

Ever since I was a little girl, I've been enveloped by the smell of lemon, rosemary, and spices. It's the smell of this Spanish perfume called Álvarez Gómez Agua de Colonia, the classic fragrance that's been made in Spain since 1912, that my grandmother, mi yaya, and my mother have always worn.

So after Rachel patiently explained to me exactly how smell worked, I had one obvious question. How do I get it back?

So after Rachel patiently explained to me exactly how smell worked, I had one obvious question. How do I get it back?

I know what you might be thinking. Same thing I was thinking when she said it. Smell training? Really? Well, Rachel walked me through it.

I know what you might be thinking. Same thing I was thinking when she said it. Smell training? Really? Well, Rachel walked me through it.

Let's actually try it together, like us. Go ahead and grab something to smell. Ready?

Let's actually try it together, like us. Go ahead and grab something to smell. Ready?

Okay, I'm using peanut butter because I love that smell. So open the jar and breathe it.

Okay, I'm using peanut butter because I love that smell. So open the jar and breathe it.

According to Rachel, studies have shown this should help smell reemerge.

According to Rachel, studies have shown this should help smell reemerge.

But Rachel says this is something anyone can and should do, even if they haven't lost their sense of smell.

But Rachel says this is something anyone can and should do, even if they haven't lost their sense of smell.

Smell is a deeply personal thing. It's a conduit for our deepest memories and thoughts. But it isn't just about what's happening in our minds. Smell has played an important role in shaping our society, in deciding who does and does not belong. Coming up, how one of the most infamous legal cases in U.S. history came down to a scent.

Smell is a deeply personal thing. It's a conduit for our deepest memories and thoughts. But it isn't just about what's happening in our minds. Smell has played an important role in shaping our society, in deciding who does and does not belong. Coming up, how one of the most infamous legal cases in U.S. history came down to a scent.

It's the smell of my yaya sitting on the couch in Madrid, with her legs crossed, wearing her kitten heel house slippers, reminiscing about being a little bit wild, un poco traviesa, as she reaches over with her soft hand to give mine a squeeze.

It's the smell of my yaya sitting on the couch in Madrid, with her legs crossed, wearing her kitten heel house slippers, reminiscing about being a little bit wild, un poco traviesa, as she reaches over with her soft hand to give mine a squeeze.

It's the smell of my mom running after me whenever I'm in my childhood home in California, with a bottle of it, trying to spritz some over my head, a fuss-fuss before we leave the house to smell fresh. And the smell of her reassuring hugs, which let me know I am never alone. SIGHS The top note is crisp, sharp, like a Mediterranean lemon whose yellow-hued brightness makes my nose tingle. SIGHS

It's the smell of my mom running after me whenever I'm in my childhood home in California, with a bottle of it, trying to spritz some over my head, a fuss-fuss before we leave the house to smell fresh. And the smell of her reassuring hugs, which let me know I am never alone. SIGHS The top note is crisp, sharp, like a Mediterranean lemon whose yellow-hued brightness makes my nose tingle. SIGHS

To smell is to learn. Sense of smell allows animals, including skunks, to detect danger and navigate their environments. We humans also use our nose to discern dangers, like the smell of a gas leak or a fire. But we've also ascribed emotions and perceptions to certain smells, associating them with feelings like fear, delight, or something putrid. And those associations aren't natural.

To smell is to learn. Sense of smell allows animals, including skunks, to detect danger and navigate their environments. We humans also use our nose to discern dangers, like the smell of a gas leak or a fire. But we've also ascribed emotions and perceptions to certain smells, associating them with feelings like fear, delight, or something putrid. And those associations aren't natural.

They're learned.

They're learned.

We create the meaning of smell. But the cultural constructs around what we decide smells good or bad can be weaponized.

We create the meaning of smell. But the cultural constructs around what we decide smells good or bad can be weaponized.

Simply put, smells can have as much of a history as a black and white photo can.

Simply put, smells can have as much of a history as a black and white photo can.

This is Mark Smith.

This is Mark Smith.

He's a sensory historian at the University of South Carolina and author of the book, A Sensory History Manifesto.

He's a sensory historian at the University of South Carolina and author of the book, A Sensory History Manifesto.

Mark says that historical writings are full of descriptions of sounds, textures, tastes, and smells.

Mark says that historical writings are full of descriptions of sounds, textures, tastes, and smells.

And those sensory descriptions can provide important details that are key to better understanding our history.

And those sensory descriptions can provide important details that are key to better understanding our history.

Yes, that Plessy v. Ferguson, the Supreme Court case that legalized separate but equal treatment. Segregation in the United States was founded in part on an argument based on racist perceptions of smell.

Yes, that Plessy v. Ferguson, the Supreme Court case that legalized separate but equal treatment. Segregation in the United States was founded in part on an argument based on racist perceptions of smell.

So to understand, we have to go back to Louisiana in 1890.

So to understand, we have to go back to Louisiana in 1890.

An educated, wealthy Black and Creole population is thriving.

An educated, wealthy Black and Creole population is thriving.

Segregation was a key part of a larger system that would later be called Jim Crow. It was a wide-ranging effort to reverse the progress Black people had made since emancipation. To achieve that, a strict separation of life for Black and white people was enforced. Separate entrances, separate schools, and one of the most public spaces at that time, railroad cars.

Segregation was a key part of a larger system that would later be called Jim Crow. It was a wide-ranging effort to reverse the progress Black people had made since emancipation. To achieve that, a strict separation of life for Black and white people was enforced. Separate entrances, separate schools, and one of the most public spaces at that time, railroad cars.

a group of prominent Black leaders, the Citizens Committee, came together and organized to specifically challenge this segregation law on train cars. So the group decided the best way to do this is to create a setup to stage an act of disobedience that will allow them to bring a case to court to challenge the law and ultimately have it struck down. Think Rosa Parks.

a group of prominent Black leaders, the Citizens Committee, came together and organized to specifically challenge this segregation law on train cars. So the group decided the best way to do this is to create a setup to stage an act of disobedience that will allow them to bring a case to court to challenge the law and ultimately have it struck down. Think Rosa Parks.

So in order to do this, they needed someone that could blur the lines of segregation.

So in order to do this, they needed someone that could blur the lines of segregation.

Before we get started, a note to listeners that this episode includes exploration of racist material.

Before we get started, a note to listeners that this episode includes exploration of racist material.

Homer Plessy. He was a shoemaker, an activist, born into a family of French-speaking Louisiana Creole people.

Homer Plessy. He was a shoemaker, an activist, born into a family of French-speaking Louisiana Creole people.

And it's because of this ambiguity that he was the perfect person to challenge the validity of segregation laws.

And it's because of this ambiguity that he was the perfect person to challenge the validity of segregation laws.

So Homer Plessy boards the whites-only car.

So Homer Plessy boards the whites-only car.

And a conductor who was in on Plessy's plan asks him if he was, quote, colored.

And a conductor who was in on Plessy's plan asks him if he was, quote, colored.

Once I let the inhale get to my chest, I reach the fragrance's heart note, and it becomes more green and fresh. And finally, when my breath makes it all the way to my belly... The base note rounds everything together. It's like the umami part of the fragrance, this kind of fullness and richness that expands throughout my whole body, like a soft hug, like home.

Once I let the inhale get to my chest, I reach the fragrance's heart note, and it becomes more green and fresh. And finally, when my breath makes it all the way to my belly... The base note rounds everything together. It's like the umami part of the fragrance, this kind of fullness and richness that expands throughout my whole body, like a soft hug, like home.

Everything went as planned. Homer Plessy was arrested and charged for violating the law. And the case went to criminal court in front of Judge John H. Ferguson.

Everything went as planned. Homer Plessy was arrested and charged for violating the law. And the case went to criminal court in front of Judge John H. Ferguson.

I can smell it.

I can smell it.

Homer Plessy was found guilty by the state, and his legal team appealed the case all the way to the Supreme Court. But the damage had already been done.

Homer Plessy was found guilty by the state, and his legal team appealed the case all the way to the Supreme Court. But the damage had already been done.

In an overwhelming 7-to-1 decision, the Supreme Court ruled against Homer Plessy, laying out the legal foundation for segregation in the United States. There's little objectivity to how we interpret what we're smelling. Most smells aren't innately good, delicious, putrid, or even foul. And yet?

In an overwhelming 7-to-1 decision, the Supreme Court ruled against Homer Plessy, laying out the legal foundation for segregation in the United States. There's little objectivity to how we interpret what we're smelling. Most smells aren't innately good, delicious, putrid, or even foul. And yet?

So next time you really like how something smells, ask yourself why. Start thinking about where you learned to like that smell and what that tells you about your history and identity. Coming up, how our sense of smell can help us understand what we can't always see, both in the past and the present.

So next time you really like how something smells, ask yourself why. Start thinking about where you learned to like that smell and what that tells you about your history and identity. Coming up, how our sense of smell can help us understand what we can't always see, both in the past and the present.

This is Ernestine Dean. She's a South African musician and medicine woman who lived for a few years in Germany. That's where she smelled those roasted almonds, a scent that took her on a journey.

This is Ernestine Dean. She's a South African musician and medicine woman who lived for a few years in Germany. That's where she smelled those roasted almonds, a scent that took her on a journey.

Ernestine may have been thousands of miles away from her childhood home in Cape Town. But in that moment, the smell of roasted nuts transported her.

Ernestine may have been thousands of miles away from her childhood home in Cape Town. But in that moment, the smell of roasted nuts transported her.

It's something that's happened to a lot of us. We smell something and all of a sudden we're jolted out of where we are into a memory of a place or a person that almost feels real.

It's something that's happened to a lot of us. We smell something and all of a sudden we're jolted out of where we are into a memory of a place or a person that almost feels real.

This is Rachel Herz again. She says the reason our smell memories are so evocative goes back to how our brain processes what we smell. When we smell something familiar, my grandma's perfume, say, or those almonds Ernestine Dean smelled in the German Christmas market, the parts of our brain that light up are also the areas that process our emotions, the amygdala, and our memories, the hippocampus.

This is Rachel Herz again. She says the reason our smell memories are so evocative goes back to how our brain processes what we smell. When we smell something familiar, my grandma's perfume, say, or those almonds Ernestine Dean smelled in the German Christmas market, the parts of our brain that light up are also the areas that process our emotions, the amygdala, and our memories, the hippocampus.

Which is why today researchers are looking at whether or not smell can improve cognition, address PTSD, and stave off dementia. And it's also why smell triggers such emotional memories that enable us to momentarily travel across time and place.

Which is why today researchers are looking at whether or not smell can improve cognition, address PTSD, and stave off dementia. And it's also why smell triggers such emotional memories that enable us to momentarily travel across time and place.

The act of smelling a perfume is like hearing a full orchestra. In order to actually smell it, your nose has to parse through thousands of different molecules, translate them, and then transmit it to your brain so that you can smell what you recognize as your favorite scent. Be it a perfume or a rose. And that's just what has to happen to smell a single thing.

The act of smelling a perfume is like hearing a full orchestra. In order to actually smell it, your nose has to parse through thousands of different molecules, translate them, and then transmit it to your brain so that you can smell what you recognize as your favorite scent. Be it a perfume or a rose. And that's just what has to happen to smell a single thing.

Ernestine says she uses these certain smells to archive her memories.

Ernestine says she uses these certain smells to archive her memories.

Bookmarks that help her remember her family's history in South Africa during the decades-long era of apartheid as mixed-heritage, indigenous Khoi people.

Bookmarks that help her remember her family's history in South Africa during the decades-long era of apartheid as mixed-heritage, indigenous Khoi people.

Under apartheid, racial discrimination and segregation were completely legalized in South Africa from 1948 to 1994. And many, like Ernestine's family, had to abandon the homes they'd known their whole lives.

Under apartheid, racial discrimination and segregation were completely legalized in South Africa from 1948 to 1994. And many, like Ernestine's family, had to abandon the homes they'd known their whole lives.

Between 1960 and 1980, an estimated 3.5 million Black and mixed-race South Africans were forced to leave their homes. Ernestine's family was part of that number. They lost their home in Constantia, a lush, fertile suburb of Cape Town, and were forced to relocate to the much drier Cape Flats and the suburban neighborhood called Grassy Park.

Between 1960 and 1980, an estimated 3.5 million Black and mixed-race South Africans were forced to leave their homes. Ernestine's family was part of that number. They lost their home in Constantia, a lush, fertile suburb of Cape Town, and were forced to relocate to the much drier Cape Flats and the suburban neighborhood called Grassy Park.

Ernestine was born after the forced removals, but she still inherited her family's deep sense of loss.

Ernestine was born after the forced removals, but she still inherited her family's deep sense of loss.

Ernestine inherited that grief, but she also inherited a connection to the land her family had to leave behind.

Ernestine inherited that grief, but she also inherited a connection to the land her family had to leave behind.

Several times a year, the whole family would go back to Constantia to bring dahlias and lilies to the tombstones in the family graveyard.

Several times a year, the whole family would go back to Constantia to bring dahlias and lilies to the tombstones in the family graveyard.

And those pinecones are what brings us back to the almonds that Ernestine smelled while visiting that German Christmas market many years later. The one that transported her back in time to her grandmother's kitchen in South Africa, to Grassy Park, and back to Constantia.

And those pinecones are what brings us back to the almonds that Ernestine smelled while visiting that German Christmas market many years later. The one that transported her back in time to her grandmother's kitchen in South Africa, to Grassy Park, and back to Constantia.

They'd roast the pine nuts, together with her grandmother, aunts and cousins, and make a traditional sweet dessert known as tamalecki.

They'd roast the pine nuts, together with her grandmother, aunts and cousins, and make a traditional sweet dessert known as tamalecki.

The reality is that for most of us, our noses are parsing through a massive number of different odor molecules a day. And it's so easy to take this riot of smell for granted. Unless it disappears. In the summer of 2022, I became one of the 15 million estimated people to have lost their sense of smell because of COVID.

The reality is that for most of us, our noses are parsing through a massive number of different odor molecules a day. And it's so easy to take this riot of smell for granted. Unless it disappears. In the summer of 2022, I became one of the 15 million estimated people to have lost their sense of smell because of COVID.

Ernestine's smell-triggered memory was layered, complex. It was happy, it was sad. It was both a window into a childhood memory and a whole country's history. And at its core, it was an act of resistance. Because at the same time that Ernestine's family was making tamaleke, the brutal system of apartheid was literally obliterating her sense of smell.

Ernestine's smell-triggered memory was layered, complex. It was happy, it was sad. It was both a window into a childhood memory and a whole country's history. And at its core, it was an act of resistance. Because at the same time that Ernestine's family was making tamaleke, the brutal system of apartheid was literally obliterating her sense of smell.

Throughout the 1980s and 90s, the anti-apartheid movement was growing in Grassy Park. And the response by the South African apartheid government was fast. Riot police were a daily presence, and the air always smelled like burning tires and tear gas.

Throughout the 1980s and 90s, the anti-apartheid movement was growing in Grassy Park. And the response by the South African apartheid government was fast. Riot police were a daily presence, and the air always smelled like burning tires and tear gas.

Tear gas is an assault on the senses. It's meant to disorient and dislocate. But in the face of that, Ernestine's family made sure she knew that the smell of pine cones, of rich, fertile earth, of dahlias and lilies, and of sweet tamaleke were part of her. That she and her family were more than burning tires and suffering.

Tear gas is an assault on the senses. It's meant to disorient and dislocate. But in the face of that, Ernestine's family made sure she knew that the smell of pine cones, of rich, fertile earth, of dahlias and lilies, and of sweet tamaleke were part of her. That she and her family were more than burning tires and suffering.

It's been 30 years since the end of apartheid in South Africa. And until recently, Ernestine lived just a few blocks from where she grew up in Grassy Park. She still goes back to Constantia, only now she's bringing her three kids and passing the smells and rituals on to them.

It's been 30 years since the end of apartheid in South Africa. And until recently, Ernestine lived just a few blocks from where she grew up in Grassy Park. She still goes back to Constantia, only now she's bringing her three kids and passing the smells and rituals on to them.

the grief is always still there. To this day, Constantia is still a predominantly white and incredibly wealthy suburb. And while there's been a real effort to restore the land evicted families lost, there's been very little traction. But Ernestine still takes her children back to tend the graves.

the grief is always still there. To this day, Constantia is still a predominantly white and incredibly wealthy suburb. And while there's been a real effort to restore the land evicted families lost, there's been very little traction. But Ernestine still takes her children back to tend the graves.

And she's found that by staying engaged with her sense of smell, there's room for healing all around her.

And she's found that by staying engaged with her sense of smell, there's room for healing all around her.

When she steps out of her house now, the toxic bouquet of burning tires and tear gas no longer clouds the air. And in its absence, she's discovered that a piece of Constantia, of her family, was always in Grassy Park.

When she steps out of her house now, the toxic bouquet of burning tires and tear gas no longer clouds the air. And in its absence, she's discovered that a piece of Constantia, of her family, was always in Grassy Park.

It's an old scent in a new place. A new bookmark in her and her family's history.

It's an old scent in a new place. A new bookmark in her and her family's history.

The minute I noticed that I wasn't able to smell anything, I ran around from room to room sniffing anything I could get my hands on. I went to the kitchen and opened a jar of peanut butter. Nothing. I took a spoonful of peanut butter and put it in my mouth. Instead of the sweet, salty, nutty flavor I expected, all I could sense was how it felt.

The minute I noticed that I wasn't able to smell anything, I ran around from room to room sniffing anything I could get my hands on. I went to the kitchen and opened a jar of peanut butter. Nothing. I took a spoonful of peanut butter and put it in my mouth. Instead of the sweet, salty, nutty flavor I expected, all I could sense was how it felt.

A year after I recorded my yaya on her couch in Madrid, she passed away. It's been over six years now, and yet I find that she's never that far from me. She lives in my memory, of course, and the recordings I have of her, of her monogram necklace that I wear around my neck. And she's embodied in the scent of Álvarez Gómez's Agua de Colonia. Yeah.

A year after I recorded my yaya on her couch in Madrid, she passed away. It's been over six years now, and yet I find that she's never that far from me. She lives in my memory, of course, and the recordings I have of her, of her monogram necklace that I wear around my neck. And she's embodied in the scent of Álvarez Gómez's Agua de Colonia. Yeah.

After months of diligently smelling an array of different scented essential oils, from lemon to clove to mint, my nose actually pricked up one day, and I felt the faint warmth of clove invade my nostrils. With time, I redeveloped the ability to smell the symphony of the world all over again. And you better believe that I doused myself in Álvarez Gómez colonia.

After months of diligently smelling an array of different scented essential oils, from lemon to clove to mint, my nose actually pricked up one day, and I felt the faint warmth of clove invade my nostrils. With time, I redeveloped the ability to smell the symphony of the world all over again. And you better believe that I doused myself in Álvarez Gómez colonia.

I smelled fresh, clean, and most importantly, I had a piece of my yaya back with me. The minute I smelled the colonia, it's like I could remember her more clearly, more fully, to the point that I could bring myself back to the moment of one of our last hugs. I love you, Yaya.

I smelled fresh, clean, and most importantly, I had a piece of my yaya back with me. The minute I smelled the colonia, it's like I could remember her more clearly, more fully, to the point that I could bring myself back to the moment of one of our last hugs. I love you, Yaya.

To this day, all I need to do is smell it, and I can conjure myself standing in the hallway of her home again, both of us in our nightgowns, hugging for well over a minute. I can hear the beep of her hearing aid, feel her tiny frame holding mine, and I smell the faint scent of Alvarez Gomez in her perfectly coiffed hair. It's like I'm there, and so is my yaya, in all her fullness.

To this day, all I need to do is smell it, and I can conjure myself standing in the hallway of her home again, both of us in our nightgowns, hugging for well over a minute. I can hear the beep of her hearing aid, feel her tiny frame holding mine, and I smell the faint scent of Alvarez Gomez in her perfectly coiffed hair. It's like I'm there, and so is my yaya, in all her fullness.

A thick, flavorless paste sticking to my tongue and gums. Finally, I ran to my bedside table where I kept my giant glass art deco bottle of Alvarez Gomez Agua de Colonia. I took a big breath, waiting for the fresh herbal scents to take over and make me feel better. But all that I inhaled was an empty void of what I knew was there, but I could no longer access.

A thick, flavorless paste sticking to my tongue and gums. Finally, I ran to my bedside table where I kept my giant glass art deco bottle of Alvarez Gomez Agua de Colonia. I took a big breath, waiting for the fresh herbal scents to take over and make me feel better. But all that I inhaled was an empty void of what I knew was there, but I could no longer access.

I went from having no sense of smell to being able to smell a chocolate wrapper from across a room. And now I have a new reason to be obsessed with smell. I recently gave birth to my first child. She's made me think about smell in a totally different way. I'm no longer just thinking about how certain smells shape my past and identity. I'm thinking about her too.

I went from having no sense of smell to being able to smell a chocolate wrapper from across a room. And now I have a new reason to be obsessed with smell. I recently gave birth to my first child. She's made me think about smell in a totally different way. I'm no longer just thinking about how certain smells shape my past and identity. I'm thinking about her too.

What smells do I want to pass down to my daughter? What scents will bookmark her life and remind her of me, of her dad, of her yaya, of who she is and where she comes from? One thing I know for certain is that she will definitely know the smell of Álvarez Gómez Colonia. And she'll know that she comes from a long line of strong Spanish women, of traviesas, like my mom and my yaya.

What smells do I want to pass down to my daughter? What scents will bookmark her life and remind her of me, of her dad, of her yaya, of who she is and where she comes from? One thing I know for certain is that she will definitely know the smell of Álvarez Gómez Colonia. And she'll know that she comes from a long line of strong Spanish women, of traviesas, like my mom and my yaya.

It felt like my tie to my mom and my grandmother was severed. After I gathered myself, I did what any journalist would do next. Hello? Okay, you are here. Okay, wonderful. And that meant calling up someone who's dedicated their life to studying and understanding smell.

It felt like my tie to my mom and my grandmother was severed. After I gathered myself, I did what any journalist would do next. Hello? Okay, you are here. Okay, wonderful. And that meant calling up someone who's dedicated their life to studying and understanding smell.

Rachel is the person for all things smell. She's the author of The Scent of Desire, Discovering Our Enigmatic Sense of Smell. And she immediately empathized with how I was feeling.

Rachel is the person for all things smell. She's the author of The Scent of Desire, Discovering Our Enigmatic Sense of Smell. And she immediately empathized with how I was feeling.

But even though our sense of smell is such an important facet of our lives, it turns out we still don't seem to know that much about it.

But even though our sense of smell is such an important facet of our lives, it turns out we still don't seem to know that much about it.

The deeper I dug into what we know about smell, the more I started to realize how much our sense of smell has shaped not just our personal experiences, but also the world we live in and our understanding of the past and the present. And it got me thinking about how smell is kind of like the science of history because it's so wrapped up in who we think we are and how we remember the past.

The deeper I dug into what we know about smell, the more I started to realize how much our sense of smell has shaped not just our personal experiences, but also the world we live in and our understanding of the past and the present. And it got me thinking about how smell is kind of like the science of history because it's so wrapped up in who we think we are and how we remember the past.

which kind of makes it the perfect ThruLine episode. So here we go. I'm Christina Kim, and today on ThruLine from NPR, I'm asking you to go on a little adventure to unpack the enigma of smell.

which kind of makes it the perfect ThruLine episode. So here we go. I'm Christina Kim, and today on ThruLine from NPR, I'm asking you to go on a little adventure to unpack the enigma of smell.

We're going to explore how olfaction actually works, from our nose to our brain, how smell has been used to legally divide us, and finally, how harnessing our sense of smell and memory can make us all into time travelers. Coming up first, how we know what we know about the science of smell.

We're going to explore how olfaction actually works, from our nose to our brain, how smell has been used to legally divide us, and finally, how harnessing our sense of smell and memory can make us all into time travelers. Coming up first, how we know what we know about the science of smell.

It's 1988, and a young scientist named Linda Buck is sitting in a laboratory at Columbia University, struggling to wrap her brain around a question.

It's 1988, and a young scientist named Linda Buck is sitting in a laboratory at Columbia University, struggling to wrap her brain around a question.

This is Linda Buck's voice from an interview she did with the American Academy of Achievement. She sat at her desk in the lab, astonished by a simple reality. One of nature's elegant designs. One many of us take for granted. I know I did. Smell. Well, at that point in 1988, scientists didn't really understand it at all.

This is Linda Buck's voice from an interview she did with the American Academy of Achievement. She sat at her desk in the lab, astonished by a simple reality. One of nature's elegant designs. One many of us take for granted. I know I did. Smell. Well, at that point in 1988, scientists didn't really understand it at all.

It may seem unbelievable, but scientists didn't understand exactly how the nose and brain were able to process and make sense of the wide range of chemicals we breathe in.

It may seem unbelievable, but scientists didn't understand exactly how the nose and brain were able to process and make sense of the wide range of chemicals we breathe in.

From that research bench at Columbia, Linda began her quest to understand how the sense of smell worked.

From that research bench at Columbia, Linda began her quest to understand how the sense of smell worked.

Linda, along with her mentor Richard Axel, invested much of her time in this research. Research that was not well-funded and largely ignored. And she passed on other job offers to study other topics along the way.

Linda, along with her mentor Richard Axel, invested much of her time in this research. Research that was not well-funded and largely ignored. And she passed on other job offers to study other topics along the way.

She ran experiment after experiment using rats, an animal whose sense of smell works similarly to humans. She studied their genetic code relentlessly. This went on for years. And then, one day.

She ran experiment after experiment using rats, an animal whose sense of smell works similarly to humans. She studied their genetic code relentlessly. This went on for years. And then, one day.

Linda and Richard Axel solved the puzzle. They'd found 1,000 smell receptors. It was just absolutely thrilling. Over the next decade, Linda Buck, Richard Axel, and their collaborators continued to build out how our brains perceive smell. Which then led to them winning the Nobel Prize in 2004. Rachel Herz says the Nobel Prize made Linda Buck into a rock star in the science world.

Linda and Richard Axel solved the puzzle. They'd found 1,000 smell receptors. It was just absolutely thrilling. Over the next decade, Linda Buck, Richard Axel, and their collaborators continued to build out how our brains perceive smell. Which then led to them winning the Nobel Prize in 2004. Rachel Herz says the Nobel Prize made Linda Buck into a rock star in the science world.

Suddenly, everyone was paying attention.

Suddenly, everyone was paying attention.

The thing that surprised me the most about all of this was we, as in humanity, knew very little about this sense that I was now learning to live without. Like the smell of onions sizzling, rain on warm concrete, or my yaya's perfume. How does that go from out there in the world, into my nose, up into my brain, and become a fundamental part of my memories, emotions, my story?

The thing that surprised me the most about all of this was we, as in humanity, knew very little about this sense that I was now learning to live without. Like the smell of onions sizzling, rain on warm concrete, or my yaya's perfume. How does that go from out there in the world, into my nose, up into my brain, and become a fundamental part of my memories, emotions, my story?

Well, after Linda Buck's discovery, we have a better understanding of how we smell, what we smell.

Well, after Linda Buck's discovery, we have a better understanding of how we smell, what we smell.

Air, what we breathe in every moment, is made of chemicals like nitrogen, oxygen, helium, that we can't actually smell, so...

Air, what we breathe in every moment, is made of chemicals like nitrogen, oxygen, helium, that we can't actually smell, so...

Today, we know that humans can detect around a trillion scents. This number dwarfs the amount of tones we can hear, about 340,000. Or shades of color we can see, around 1 million.

Today, we know that humans can detect around a trillion scents. This number dwarfs the amount of tones we can hear, about 340,000. Or shades of color we can see, around 1 million.

This is because smell was extremely important for our prehistoric ancestors who lived in an inhospitable world. A world where they needed to be able to smell predators or prey from long distances away. A world where their instincts were driven by the smells they encountered on a daily basis. And the accuracy of those instincts were often the difference between life and death.

This is because smell was extremely important for our prehistoric ancestors who lived in an inhospitable world. A world where they needed to be able to smell predators or prey from long distances away. A world where their instincts were driven by the smells they encountered on a daily basis. And the accuracy of those instincts were often the difference between life and death.

And with each breath, we are carrying in the odors in the air.

And with each breath, we are carrying in the odors in the air.

The odor molecules move up and up, lightning fast.

The genes responsible for those receptors are what Linda Buck discovered in 1991. They detect the chemicals, then start communicating with other neurons that will carry that information to a part of the brain that processes scent. And that's the amygdala hippocampal complex.

This also happens to be the part of the brain where our emotions and memories are processed.

Ever since I was a little girl, I've been enveloped by the smell of lemon, rosemary, and spices. It's the smell of this Spanish perfume called Álvarez Gómez Agua de Colonia, the classic fragrance that's been made in Spain since 1912, that my grandmother, mi yaya, and my mother have always worn.

So after Rachel patiently explained to me exactly how smell worked, I had one obvious question. How do I get it back?

I know what you might be thinking. Same thing I was thinking when she said it. Smell training? Really? Well, Rachel walked me through it.

Let's actually try it together, like us. Go ahead and grab something to smell. Ready?

Okay, I'm using peanut butter because I love that smell. So open the jar and breathe it.

According to Rachel, studies have shown this should help smell reemerge.

But Rachel says this is something anyone can and should do, even if they haven't lost their sense of smell.

Smell is a deeply personal thing. It's a conduit for our deepest memories and thoughts. But it isn't just about what's happening in our minds. Smell has played an important role in shaping our society, in deciding who does and does not belong. Coming up, how one of the most infamous legal cases in U.S. history came down to a scent.

It's the smell of my yaya sitting on the couch in Madrid, with her legs crossed, wearing her kitten heel house slippers, reminiscing about being a little bit wild, un poco traviesa, as she reaches over with her soft hand to give mine a squeeze.

It's the smell of my mom running after me whenever I'm in my childhood home in California, with a bottle of it, trying to spritz some over my head, a fuss-fuss before we leave the house to smell fresh. And the smell of her reassuring hugs, which let me know I am never alone. SIGHS The top note is crisp, sharp, like a Mediterranean lemon whose yellow-hued brightness makes my nose tingle. SIGHS

To smell is to learn. Sense of smell allows animals, including skunks, to detect danger and navigate their environments. We humans also use our nose to discern dangers, like the smell of a gas leak or a fire. But we've also ascribed emotions and perceptions to certain smells, associating them with feelings like fear, delight, or something putrid. And those associations aren't natural.

They're learned.

We create the meaning of smell. But the cultural constructs around what we decide smells good or bad can be weaponized.

Simply put, smells can have as much of a history as a black and white photo can.

This is Mark Smith.

He's a sensory historian at the University of South Carolina and author of the book, A Sensory History Manifesto.

Mark says that historical writings are full of descriptions of sounds, textures, tastes, and smells.

And those sensory descriptions can provide important details that are key to better understanding our history.

Yes, that Plessy v. Ferguson, the Supreme Court case that legalized separate but equal treatment. Segregation in the United States was founded in part on an argument based on racist perceptions of smell.

So to understand, we have to go back to Louisiana in 1890.

An educated, wealthy Black and Creole population is thriving.

Segregation was a key part of a larger system that would later be called Jim Crow. It was a wide-ranging effort to reverse the progress Black people had made since emancipation. To achieve that, a strict separation of life for Black and white people was enforced. Separate entrances, separate schools, and one of the most public spaces at that time, railroad cars.

a group of prominent Black leaders, the Citizens Committee, came together and organized to specifically challenge this segregation law on train cars. So the group decided the best way to do this is to create a setup to stage an act of disobedience that will allow them to bring a case to court to challenge the law and ultimately have it struck down. Think Rosa Parks.

So in order to do this, they needed someone that could blur the lines of segregation.

Before we get started, a note to listeners that this episode includes exploration of racist material.

Homer Plessy. He was a shoemaker, an activist, born into a family of French-speaking Louisiana Creole people.

And it's because of this ambiguity that he was the perfect person to challenge the validity of segregation laws.

So Homer Plessy boards the whites-only car.

And a conductor who was in on Plessy's plan asks him if he was, quote, colored.

Once I let the inhale get to my chest, I reach the fragrance's heart note, and it becomes more green and fresh. And finally, when my breath makes it all the way to my belly... The base note rounds everything together. It's like the umami part of the fragrance, this kind of fullness and richness that expands throughout my whole body, like a soft hug, like home.

Everything went as planned. Homer Plessy was arrested and charged for violating the law. And the case went to criminal court in front of Judge John H. Ferguson.

I can smell it.

Homer Plessy was found guilty by the state, and his legal team appealed the case all the way to the Supreme Court. But the damage had already been done.

In an overwhelming 7-to-1 decision, the Supreme Court ruled against Homer Plessy, laying out the legal foundation for segregation in the United States. There's little objectivity to how we interpret what we're smelling. Most smells aren't innately good, delicious, putrid, or even foul. And yet?

So next time you really like how something smells, ask yourself why. Start thinking about where you learned to like that smell and what that tells you about your history and identity. Coming up, how our sense of smell can help us understand what we can't always see, both in the past and the present.

This is Ernestine Dean. She's a South African musician and medicine woman who lived for a few years in Germany. That's where she smelled those roasted almonds, a scent that took her on a journey.

Ernestine may have been thousands of miles away from her childhood home in Cape Town. But in that moment, the smell of roasted nuts transported her.

It's something that's happened to a lot of us. We smell something and all of a sudden we're jolted out of where we are into a memory of a place or a person that almost feels real.

This is Rachel Herz again. She says the reason our smell memories are so evocative goes back to how our brain processes what we smell. When we smell something familiar, my grandma's perfume, say, or those almonds Ernestine Dean smelled in the German Christmas market, the parts of our brain that light up are also the areas that process our emotions, the amygdala, and our memories, the hippocampus.

Which is why today researchers are looking at whether or not smell can improve cognition, address PTSD, and stave off dementia. And it's also why smell triggers such emotional memories that enable us to momentarily travel across time and place.

The act of smelling a perfume is like hearing a full orchestra. In order to actually smell it, your nose has to parse through thousands of different molecules, translate them, and then transmit it to your brain so that you can smell what you recognize as your favorite scent. Be it a perfume or a rose. And that's just what has to happen to smell a single thing.

Ernestine says she uses these certain smells to archive her memories.

Bookmarks that help her remember her family's history in South Africa during the decades-long era of apartheid as mixed-heritage, indigenous Khoi people.

Under apartheid, racial discrimination and segregation were completely legalized in South Africa from 1948 to 1994. And many, like Ernestine's family, had to abandon the homes they'd known their whole lives.

Between 1960 and 1980, an estimated 3.5 million Black and mixed-race South Africans were forced to leave their homes. Ernestine's family was part of that number. They lost their home in Constantia, a lush, fertile suburb of Cape Town, and were forced to relocate to the much drier Cape Flats and the suburban neighborhood called Grassy Park.

Ernestine was born after the forced removals, but she still inherited her family's deep sense of loss.

Ernestine inherited that grief, but she also inherited a connection to the land her family had to leave behind.

Several times a year, the whole family would go back to Constantia to bring dahlias and lilies to the tombstones in the family graveyard.

And those pinecones are what brings us back to the almonds that Ernestine smelled while visiting that German Christmas market many years later. The one that transported her back in time to her grandmother's kitchen in South Africa, to Grassy Park, and back to Constantia.

They'd roast the pine nuts, together with her grandmother, aunts and cousins, and make a traditional sweet dessert known as tamalecki.

The reality is that for most of us, our noses are parsing through a massive number of different odor molecules a day. And it's so easy to take this riot of smell for granted. Unless it disappears. In the summer of 2022, I became one of the 15 million estimated people to have lost their sense of smell because of COVID.

Ernestine's smell-triggered memory was layered, complex. It was happy, it was sad. It was both a window into a childhood memory and a whole country's history. And at its core, it was an act of resistance. Because at the same time that Ernestine's family was making tamaleke, the brutal system of apartheid was literally obliterating her sense of smell.

Throughout the 1980s and 90s, the anti-apartheid movement was growing in Grassy Park. And the response by the South African apartheid government was fast. Riot police were a daily presence, and the air always smelled like burning tires and tear gas.

Tear gas is an assault on the senses. It's meant to disorient and dislocate. But in the face of that, Ernestine's family made sure she knew that the smell of pine cones, of rich, fertile earth, of dahlias and lilies, and of sweet tamaleke were part of her. That she and her family were more than burning tires and suffering.

It's been 30 years since the end of apartheid in South Africa. And until recently, Ernestine lived just a few blocks from where she grew up in Grassy Park. She still goes back to Constantia, only now she's bringing her three kids and passing the smells and rituals on to them.

the grief is always still there. To this day, Constantia is still a predominantly white and incredibly wealthy suburb. And while there's been a real effort to restore the land evicted families lost, there's been very little traction. But Ernestine still takes her children back to tend the graves.

And she's found that by staying engaged with her sense of smell, there's room for healing all around her.

When she steps out of her house now, the toxic bouquet of burning tires and tear gas no longer clouds the air. And in its absence, she's discovered that a piece of Constantia, of her family, was always in Grassy Park.

It's an old scent in a new place. A new bookmark in her and her family's history.

The minute I noticed that I wasn't able to smell anything, I ran around from room to room sniffing anything I could get my hands on. I went to the kitchen and opened a jar of peanut butter. Nothing. I took a spoonful of peanut butter and put it in my mouth. Instead of the sweet, salty, nutty flavor I expected, all I could sense was how it felt.

A year after I recorded my yaya on her couch in Madrid, she passed away. It's been over six years now, and yet I find that she's never that far from me. She lives in my memory, of course, and the recordings I have of her, of her monogram necklace that I wear around my neck. And she's embodied in the scent of Álvarez Gómez's Agua de Colonia. Yeah.

After months of diligently smelling an array of different scented essential oils, from lemon to clove to mint, my nose actually pricked up one day, and I felt the faint warmth of clove invade my nostrils. With time, I redeveloped the ability to smell the symphony of the world all over again. And you better believe that I doused myself in Álvarez Gómez colonia.

I smelled fresh, clean, and most importantly, I had a piece of my yaya back with me. The minute I smelled the colonia, it's like I could remember her more clearly, more fully, to the point that I could bring myself back to the moment of one of our last hugs. I love you, Yaya.

To this day, all I need to do is smell it, and I can conjure myself standing in the hallway of her home again, both of us in our nightgowns, hugging for well over a minute. I can hear the beep of her hearing aid, feel her tiny frame holding mine, and I smell the faint scent of Alvarez Gomez in her perfectly coiffed hair. It's like I'm there, and so is my yaya, in all her fullness.

A thick, flavorless paste sticking to my tongue and gums. Finally, I ran to my bedside table where I kept my giant glass art deco bottle of Alvarez Gomez Agua de Colonia. I took a big breath, waiting for the fresh herbal scents to take over and make me feel better. But all that I inhaled was an empty void of what I knew was there, but I could no longer access.

I went from having no sense of smell to being able to smell a chocolate wrapper from across a room. And now I have a new reason to be obsessed with smell. I recently gave birth to my first child. She's made me think about smell in a totally different way. I'm no longer just thinking about how certain smells shape my past and identity. I'm thinking about her too.

What smells do I want to pass down to my daughter? What scents will bookmark her life and remind her of me, of her dad, of her yaya, of who she is and where she comes from? One thing I know for certain is that she will definitely know the smell of Álvarez Gómez Colonia. And she'll know that she comes from a long line of strong Spanish women, of traviesas, like my mom and my yaya.

It felt like my tie to my mom and my grandmother was severed. After I gathered myself, I did what any journalist would do next. Hello? Okay, you are here. Okay, wonderful. And that meant calling up someone who's dedicated their life to studying and understanding smell.

Rachel is the person for all things smell. She's the author of The Scent of Desire, Discovering Our Enigmatic Sense of Smell. And she immediately empathized with how I was feeling.

But even though our sense of smell is such an important facet of our lives, it turns out we still don't seem to know that much about it.

The deeper I dug into what we know about smell, the more I started to realize how much our sense of smell has shaped not just our personal experiences, but also the world we live in and our understanding of the past and the present. And it got me thinking about how smell is kind of like the science of history because it's so wrapped up in who we think we are and how we remember the past.

which kind of makes it the perfect ThruLine episode. So here we go. I'm Christina Kim, and today on ThruLine from NPR, I'm asking you to go on a little adventure to unpack the enigma of smell.

We're going to explore how olfaction actually works, from our nose to our brain, how smell has been used to legally divide us, and finally, how harnessing our sense of smell and memory can make us all into time travelers. Coming up first, how we know what we know about the science of smell.

It's 1988, and a young scientist named Linda Buck is sitting in a laboratory at Columbia University, struggling to wrap her brain around a question.

This is Linda Buck's voice from an interview she did with the American Academy of Achievement. She sat at her desk in the lab, astonished by a simple reality. One of nature's elegant designs. One many of us take for granted. I know I did. Smell. Well, at that point in 1988, scientists didn't really understand it at all.

It may seem unbelievable, but scientists didn't understand exactly how the nose and brain were able to process and make sense of the wide range of chemicals we breathe in.

From that research bench at Columbia, Linda began her quest to understand how the sense of smell worked.

Linda, along with her mentor Richard Axel, invested much of her time in this research. Research that was not well-funded and largely ignored. And she passed on other job offers to study other topics along the way.

She ran experiment after experiment using rats, an animal whose sense of smell works similarly to humans. She studied their genetic code relentlessly. This went on for years. And then, one day.

Linda and Richard Axel solved the puzzle. They'd found 1,000 smell receptors. It was just absolutely thrilling. Over the next decade, Linda Buck, Richard Axel, and their collaborators continued to build out how our brains perceive smell. Which then led to them winning the Nobel Prize in 2004. Rachel Herz says the Nobel Prize made Linda Buck into a rock star in the science world.

Suddenly, everyone was paying attention.

The thing that surprised me the most about all of this was we, as in humanity, knew very little about this sense that I was now learning to live without. Like the smell of onions sizzling, rain on warm concrete, or my yaya's perfume. How does that go from out there in the world, into my nose, up into my brain, and become a fundamental part of my memories, emotions, my story?

Well, after Linda Buck's discovery, we have a better understanding of how we smell, what we smell.

Air, what we breathe in every moment, is made of chemicals like nitrogen, oxygen, helium, that we can't actually smell, so...

Today, we know that humans can detect around a trillion scents. This number dwarfs the amount of tones we can hear, about 340,000. Or shades of color we can see, around 1 million.

This is because smell was extremely important for our prehistoric ancestors who lived in an inhospitable world. A world where they needed to be able to smell predators or prey from long distances away. A world where their instincts were driven by the smells they encountered on a daily basis. And the accuracy of those instincts were often the difference between life and death.

And with each breath, we are carrying in the odors in the air.