Episode Summary
Executive Summary: This Through Line episode explores smell as a scientific mystery, a tool of identity and memory, and a weapon of social control. It traces the neuroscience of olfaction, the history of smell research, racist uses of smell in Plessy v. Ferguson and apartheid, and the role scent plays in preserving personal and family history.
Main Topics: The science of smell (Priority: 5/5): Explains how odor molecules are detected by receptors in the nose and processed in brain regions tied to emotion and memory. Linda Buck and the breakthrough in olfaction research (Priority: 5/5): Describes how Linda Buck and Richard Axel identified the smell receptor gene family, launching major advances in understanding smell. Smell, memory, and identity (Priority: 5/5): Shows how scent evokes vivid autobiographical memories and becomes a 'bookmark' for personal and family history. Smell as a tool of racism and legal exclusion (Priority: 5/5): Examines how racist ideas about smell helped justify segregation and shaped the Plessy v. Ferguson case. Apartheid and sensory violence (Priority: 4/5): Uses Ernestine Dean’s memories to show how smell, including tear gas and burning tires, carried both trauma and cultural resistance under apartheid. Smell loss and recovery (Priority: 4/5): Discusses COVID-related anosmia and smell training as a way to regain smell and reconnect with memory and well-being.
Key Arguments: Smell is deeply linked to emotion and memory because olfactory processing overlaps with brain regions such as the amygdala and hippocampus. Scientific understanding of smell lagged behind other senses until Linda Buck and Richard Axel identified a large family of odor receptors. Humans can detect an extraordinarily large range of scents, reflecting smell’s evolutionary importance for survival. Smell is not purely biological; cultural learning and personal experience shape whether a scent is perceived as pleasant or unpleasant. Racist and exclusionary systems can weaponize smell by presenting subjective judgments as objective truth, as in Plessy v. Ferguson. Sensory history reveals what standard visual history misses, including the smells and sensory cues that structure power, belonging, and exclusion. Smell can function as a time machine, bringing people back to specific people, places, and inherited histories. Smell training can help some people regain odor perception after smell loss and may have broader cognitive and health benefits.
Data Points: People estimated to have lost smell due to COVID: 15 million - Mentioned when the reporter describes becoming anosmic in summer 2022. Smell receptors discovered: About 1,000 - Linda Buck and Richard Axel identified roughly a thousand smell receptors. Odors humans can detect: Around 1 trillion scents - Used to emphasize how sensitive human olfaction is. Tones humans can hear: About 340,000 - Compared with the number of scents humans can detect. Shades of color humans can see: Around 1 million - Used as a comparison showing smell exceeds other senses in scale. Supreme Court decision in Plessy v. Ferguson: 7-1 - The Court ruled against Homer Plessy, validating segregation. Apartheid forced removals: An estimated 3.5 million - Black and mixed-race South Africans were forced from homes between 1960 and 1980. Apartheid era: 1948 to 1994 - Describes the official period of legalized racial segregation in South Africa. Smell training frequency: At least 3 times a day for 12 weeks - Rachel Herz recommends this routine for smell recovery.
Pivotal Quotes: "To smell is to feel." — Rachel Herz: A concise summary of the episode’s core neuroscience point about smell, emotion, and memory. "I can smell it. I can smell it." — Louisiana prosecutor in Plessy v. Ferguson, as recounted in the episode: Illustrates how racist claims about smell were used to justify segregation. "Who we are is a collection of the stories of our past...and absolutely, scent is the key to that." — Rachel Herz: Explains the episode’s central argument that smell anchors identity and memory.
Implications: The episode suggests smell is a powerful but underappreciated force shaping health, memory, identity, and injustice. Paying attention to scent can deepen historical understanding, support recovery from smell loss, and reveal how power is encoded in everyday perception.