The smell, that sense that Western tradition placed in the lowest step of the sensory hierarchy, is now revealed as a sophisticated biological tool that not only keeps us alive, but also weaves the invisible fabric of our social life, identity and memory.
But there is a fundamental distance that we must go through: the one that separates what the smell does in our body (its biological functions) of what we We do with him (his cultural uses "nodes"). Biology gives us an extraordinarily sensitive chemical detection system; culture, for its part, turns that capacity into rituals, prejudices, shared memories and care technologies. To understand this distinction is to understand something essential about ourselves, as would the Oracle of Delphs "Know yourself and you will know the universe and all the gods"
The Biological Functions
Before we ask ourselves why incense brings us to the sacred or why the smell of the mother calms the baby, we must understand the scaffolding on which all that is built. Neurobiological research, particularly the work of Richard Stevenson (2010) and the reviews of equipment such as Boesveldt and Graaf (2017), have identified several fundamental biological functions of human smell.
The first is the ingestive function. The smell evaluates the food before they enter our mouth (via ortonasal) and while we chew it (via retronasal), deciding whether they are appropriate or dangerous. When the milk smells sour, we are witnessing a biological warning system as subtle as it is sophisticated: volatile molecules released by bacteria activate specific receptors that, in the thousands of seconds, generate a rejection response that protects us from intoxication.
The second is the avoidance of dangers. As Santos and collaborators (2004) documented, people with loss of smell suffer much more often from domestic accidents. The smoke, the gas, the decomposing chemicals: the smell is a silent sentinel that works while we think of other things, connecting directly to avoidance motor circuits that operate before we are aware of the danger.
The third is social communication and reproduction. From the pioneering experiment of Claus Wedekind (1995) on couples' preference with complementary immune system, to the studies of Jasper de Groot and his team (2015) on the chemical transmission of fear and happiness through sweat, we know that our bodies emit and receive messages that never become words. The sweat of someone who is afraid, for example, activates our tonsils and prepares us for the threat without us knowing why.
The fourth function is attachment and bond. Ruth Feldman (2021) showed that the maternal smell, even in a used T-shirt, improves the brain synchrony between a baby and an unknown adult. The smell of the child itself, for its part, activates reward circuits in the parents' brain, as Schäfer and colleagues showed (2024). There is a care chemistry that operates below every conscious decision.
The fifth is hedonic evaluation: the ability to feel pleasure or disgust at a smell. Far from being an aesthetic preference, this evaluation is a behavioral orientation system that drives us to the nutritious and takes us away from the pathogen. Research such as those of Zhang and collaborators (2017) have identified specific brain routes, the projection from the ventrical tegmental area to the olfactory tuber, which generate preference for certain aromas and associate pleasant experiences to certain odors.
The sixth, perhaps the most surprising, is spatial orientation. Biologist Lucia Jacobs (2012) proposed that the smell evolved primarily for navigation: to predict where things are in space. Subsequent studies of Bao and his team (2019) confirmed that the human brain uses the same "grid" cells to navigate physical spaces as to guide itself on odour maps. Oler is, in this sense, a way of mapping the world.
These six functions constitute the biological basis. But the tools do not determine their use.
The Cultural Construction of the Olor
What happens when we move from function to use is a qualitative leap. Biology provides us with the ability to detect, evaluate and remember odors; culture teaches us what smell, how interpret it and for what use it. In previous articles (Nodes) we have carefully explored each of these uses, the smell as collective cohesion, as a social border, as a living memory, as a bridge to the sacred, as an intimate geography, as a technology of self, as a shelter and care, but what matters now is to understand their common logic, which is that all these cultural uses share a fundamental feature: they take on a biological capacity. —chemical detection— and make it a system of meanings.
Let's go back to Nietzsche. When he wrote "my genius is in my nose," he spoke not only of his literal olfactory capacity, but of his acuity to perceive what others do not perceive: the smell of decadence, hypocrisy, life that denies itself. His olfactory genius was, above all, a form of knowledge. We know with hounds among other mammals have a higher olfactory sensitivity than human, even it has been said that they can "smell emotions" and what if we accompanied by other signs from other senses can somehow olfatively detect those emotions?
The six biological functions of the smell, to detect food, to avoid dangers, to communicate with us socially, to link us affectively, to evaluate hedonically, to orient us in space, are the scaffolding on which we build extraordinarily diverse cultural uses. We have used the smell to create community and to establish hierarchies, to remember who we are and to connect with the divine, to inhabit the territory and to build our most intimate identity, to comfort ourselves in vulnerability and to regulate our own being.
Every time we inhale, an incense in a ceremony, the perfume of a loved one, the aroma of the street that was our childhood, we are going through that bridge between biology and culture. We are, without knowing it, being philosophical with our nose. What we are is, ultimately, as Daniel H. Lende and Greg Downey would say, a "built-in brain" proof that the most biological is always available to become the most cultural, and that the most intimate, an odor that moves us without knowing why, has roots in the adaptations and evolution of our species.
