Why smell jumps the queue when it comes to memories

Smells hardwire deep into the brain, writes Henna Cundill, as she explores why they jump-start such vivid memories.

Henna Cundill

Henna is a researcher with the Centre for Autism and Theology at the University of Aberdeen.

An autumnal scene of a church yard and church framed by leafless trees.

'The smell of dust and damp stone will always cry “safety!”'

Jakub Pabis on Unsplash.

When I was a 22-year-old undergraduate my mother died quite suddenly. I can't remember the name of the undertakers we used, nor the chaplain who took her funeral. I can no longer visualise what any of their faces looked like. I know I visited the chaplain’s house to plan the funeral, but I can't remember exactly where that house was. What sticks is that the day of the funeral was a sultry summer's day, and both the chaplain and the undertakers smelt of perspiration. To this day there are moments where I catch that same whiff of man-sweat in some other location, and for a fleeting second, I am a bewildered 22-year-old once more.

Here is another memory. I attended a tiny, rural Church of England primary school in the middle of England. At the end of each school year, all of us donned our little Wellington boots, which smelt faintly of slurry (since this was dairy-farming country) and sweaty feet. Then we lined up in a crocodile and trudged through the bluebell-wood (damp leaves) and skirted the edge of fields (silage, which stings the nose) covering the mile or so between our school building and the village church.

We would enter the church grounds through the back field, hurrying through an eerily muffled graveyard with tombstones towering far above our heads and the grass disturbingly lumpy beneath our little feet. To the chidings of “Quickly!” and “Quietly!” we children scurried down a gravel path, away from this unsettling place of death, to reach the cool sanctuary of a little church, and the comforting smells (for me, at least) of damp stone and dusty hymnbooks.

Others may not have the same associations, but for me the smell of dust and damp stone will always cry “safety!” and the reassurance that “there are no ghosts in here!” in contrast to that troubling graveyard. From death to life. Yet, at the same time, getting stuck with my nose close to some man’s whiffy armpit on the Tube will forever insinuate that I am just a child pretending to be a grown-up, out of my depth, overwhelmed with one thousand decisions to make (“What flowers do you want for her coffin?”) and no-one to advise. In the midst of life, death again.

On reflection I will know that my emotions are being manipulated by my nose, in ways which are more or less than helpful depending on the circumstances.

Of course, I am not 22 years old and lost anymore, no matter what that man’s armpit tries to tell me. My rational mind knows better, but my rational mind doesn’t get a say – or doesn’t get the first say anyway. This is because smell is the only one of our senses that bypasses the thalamus (the brain’s ‘filtering gate’ that decides which part of the brain needs to respond to sensory input) and goes straight to the limbic system, where emotional memory is stored.

Sometimes it is very obvious that this is taking place, such as in the examples given above. On reflection I will know that my emotions are being manipulated by my nose, in ways which are more or less than helpful depending on the circumstances. But it can happen in more subtle ways too. Supermarkets infamously pump out smells to influence our buying choices, and we’re trying to sell our house right now, so we’ve been brewing a whole lot more coffee than we ever usually would.

Intriguingly, scientists don’t really know why the human sense of smell jumps the queue when it comes to cognitive processing. There are biological theories, such as that the smell of predator could wake up our ancestors while they were sleeping and/or could allow them to follow a scent trail quickly when fleeing danger or seeking food. There are social theories too, such as that we don’t have a lot of good words to describe smells, so the brain just doesn’t bother trying to analyse them. Whatever the truth of the matter, the reality is that (whether we like it or not) our noses are an emotional trip-hazard.

When I walk through those great oak doors there is a moment, a glitch in the matrix, when the unmistakable smell of church hits my nose. Dust, damp… a little hint of mouse.

I can’t help wondering what this tells me about my religious practice. Do I go to church because I have made a cognitive decision to worship God each Sunday? Or do I go to church because I am following my nose, getting away from a world full of armpits and responsibilities to a place where I am a seven-year-old girl, all gingham dress and wellies, feeling safe. If so, does it matter?

Truth is, my mind can give me a dozen reasons not to go to church every single week. In fact, two dozen reasons. More. It has always been a busy week; I’m always behind on work. The house always needs a sort out and the car is never washed. But because certain congregation members are normally counting on me for certain things, and because I’m still pretending to be a grown up, I typically drag myself out the door, and off to church I go.

And week on week, without fail, when I walk through those great oak doors there is a moment, a glitch in the matrix, when the unmistakable smell of church hits my nose. Dust, damp… a little hint of mouse. My body registers this before my mind; my shoulders drop a little of their tension. Even if it’s just for a fleeting moment, I start to feel that I know for sure what is absolutely real in my life and what is just pretend.

Is this knowledge irrational – since it doesn’t come from the cognitive part of my mind? Or is there a God who knows that the cognitive part of my mind sometimes tells me all sorts of untrue and unhelpful things. Is there a God who is choosing to reach out to me in more subtle, more ancient ways?

I can only wonder if I have been following my nose all this time, without even noticing. Drawn along by an ancient scent trail that leads me time and time again…this way…and that way…until I reach a place where there is safety, and bread.

Explainer

Biology

Culture

Ethics

24 May 2023

8 min read

Inheritance and environment's impact on ethics

Once discounted insights are now found important and have ethical consequences. Andrew Davison concludes his series on biology’s current developments.

Andrew Davison

Andrew works at the intersection of theology, science and philosophy. He is Canon and Regius Professor of Divinity at Christ Church, Oxford.

A wall tile shows a 1940s woman tend a stove below a washing line.

A commemorative tile honours Dutch woman who made 'something out of nothing. during the hunger winter.

Peter de Wit (FaceMePLS), CC BY 2.0, via Wikimedia Commons

There’s no more exciting work in biology at the moment than thinking about organisms in terms of their environment. That’s a crucial part of the lively current scene in evolutionary thought (which I described in my previous article), and part of how a new generation of fascinating writers is urging us to throw off the overly narrow perspectives of the twentieth century. It’s not that Darwin’s fundamental insights were wrong, just that some of his followers took them to rule out, or discount, features of biology that turn out to be real and important.

In fact, Darwin was often ahead of the game here. He was more interested in cooperation between species, for instance, than many writers who went on to champion his ideas. He wrote brilliantly about the relationship between moths and orchids, for instance, and between plants and earthworms. Similarly, as Jessica Riskin has recently pointed out, he never dropped the idea that what organisms do during their lifetime affects what they pass on to their offspring (what he called ‘use and disuse’). For much of the twentieth century, that idea, of passing on of acquired characteristics, was biological heresy, but today it’s making a comeback.

The excitement in contemporary evolutionary biology can usefully be gathered under two headings. Alongside ‘organism and environment’, there’s also ‘extended heredity’, although the two are closely related on some points. They’re both important as part of the sort of discussion presented on this site – run in conjunction with the Church of England, of all things – not just because it’s good for religious institutions to demonstrate enthusiasm for science, but also because they’re full of ethical consequences.

Passing on to the progeny

Take ‘extended inheritance’: extended, in the sense that there’s so much more that’s inherited from parent to child than just a DNA sequence. For one thing, every organism bequeaths a world to its progeny, which means a world that’s at least somewhat adapted: at least a little (as with some bacteria, although others are adept at ‘ecosystem engineering’) or massively, as when a beaver completely changes its surroundings by building a dam, or when human beings cover the Earth with marvellous and terrible things. The transformed landscape of the beaver and the human being, even of the bacterium, is part and parcel of what they each pass on to their progeny, and therefore part of biological inheritance. That really puts the environment back at the centre of our thinking about organisms and evolution.

Taking a wider view than genes-are-all-you-pass-on has no lack of consequences. In their accessible and endlessly fascinating 2018 book Extended Heredity, Russell Bonduriansky and Troy Day show that narrow-mindedness on that front has had terrible consequences. They see it behind the Thalidomide birth defect tragedy, for instance, and the strange unwillingness of medics, in the middle of the twentieth century, to take the dangers of foetal alcohol syndrome seriously. If it’s a matter of scientific dogma that all that matters is what genes parents give to their offspring, other factors – like bothering to monitor what effects alcohol have on pregnant women and developing child, or the effects on them of a new medicine – don’t look as important as they should.

Genes aren’t everything, especially in the developmental phase (from conception through childhood and adolescence). Throughout that period, in particular, genes and environment dance an intimate tango, with genes turning on and off in response to its experience of its environment, before and after birth. Moreover, recent science shows that what happens to you during your lifetime can even be passed onto your offspring, and even to their children after them.

That flies in the face of the idea that all you have to pass on is the genetic hand of cards you were delt at conception (or its equivalent, for instance for a plant). On that hallowed view, the most that life has to offer from that moment on is testing your ‘fitness’, to see whether you manage to pass those genes on, or not, or how abundantly. But that’s far too limited a picture. We don’t just pass on genes; we also pass on the pattern of how genes are tagged to be turned on or off, and that is changed by the conditions the organism has experienced.

Hunger lessons

The most striking, but gruesome, example involving human beings is the ‘Dutch Hunger Winter’ of 1944–45, when occupying German forces starved the Dutch population in retaliation for resistance victories. Children conceived during that period grew up with poor metabolism (or, to be more accurate, metabolism that would be good at surviving starvation, but was not well-adapted to healthier post-war life nutrition, which is fascinating in itself). So much for genes being everything. More startling still was the observation that their children also had poor metabolism: the grandchildren of the starved pregnant women. We can pass on acquired characteristics, which really puts the cat among the twentieth century Darwinian pigeons. As the prophet Ezekiel put it, ‘The parents have eaten sour grapes, and the children’s teeth are set on edge’. This is full of ethical freight. The way we treat other people, and ourselves, affects those who come after us: yes, socially and culturally, which is significant enough, but even in how their bodies are programmed to develop.

A stimulating environment

There’s a similar ethical charge to what is perhaps my favourite part of the newly boisterous world of biology: phenotypic plasticity. That’s the simple idea that the same genes (the ‘genotype’) will produce a differently structured organism (the ‘phenotype’) in response to different environments. In one sense, it’s obvious enough. If I go to the gym for a year – a particular kind of environment – I’ll look different afterwards than if I’d spend an equivalent length of time on the sofa.

But it goes much further than that. Various plants will produce different sorts of leaves, for instance, depending on whether they grow in more or less shady situations. Sometimes, one species can be mistaken for two, as happened with fish, called cichlids, in Lake Tanganyika (between Tanzania and the Democratic Republic of Congo). What scientists had thought to be separate species, because their jaws are so different, turned out to be the same species. If a fish grows up at the bottom of the lake, it develops one mouth shape, with large, strong jaws, for munching shellfish; if a it with the same genes grows up at the top of the lake, it develops delicate jaws, useful for eating other kinds of food.

Again, the repercussions of ethics are enormous, and that brings us back to the ugly subject of eugenics, mentioned in the first of these articles. At root, eugenics is based on the assumption that some people just are healthy, and others just are sick, because some have ‘good genes’, while others have ‘bad genes’. You are either blessed with the former, or doomed with the later, and that’s set in stone, from conception. It’s then (supposedly) the ‘right thing’ to promote the former when it comes to reproduction and, at its most horrific, to restrain, sterilise, or even slaughter the latter. Eugenics cast its shadow over more of the twentieth century than we might like to admit. At one time or another, it was the darling of both the political right and the political left. It hasn’t gone away.

Before we say anything else, there’s a moral flaw in thinking that concern for the gene pool trumps concern for suffering individuals. More than that, though, the biology shows eugenics to be flawed even on its own, supposedly scientific, terms. We aren’t just blessed or doomed by the genetic hand of cards we’re delt at conception. Like those plants, growing in sunlight or shade, what our genes will mean is also determined by our setting. Like those African fish, our genes can run more than one programme, so the environment matters.

Eugenics presents the all-to-convenient picture that the sick will be sick, the weak will be weak, and that’s that. But we’re not just doomed or blessed by genes. It matters, for instance, what sort of housing we have, how we’re fed, and whether we have access to fresh air and places for exercise, and to stimulus for the mind, and companionship. Putting people into groups (healthy and sick, or worthy and unworthy), then writing off one of those groups might be politically and economically convenient, but it’s bad science, as well as bad morals.

Reason to be curious

I started this series by mentioning how important the theology and philosophy of the Middle Ages has been for me, in working between theology and science. In one of his little read works, Thomas Aquinas (1224–1274) defended having the expansive curriculum used in training Dominican friars like himself. (It helped that this curriculum was being drawn up, in part, by Albert the Great – perhaps the greatest polymath of his century, and later patron saint of scientists.) One should be open to knowing about everything, Aquinas argued, because you never know what will come in useful later on. We have an excellent, and timely example of that, in how something as obscure as phenotypic plasticity bears on eugenics, and the eminently practical question of proper housing.

Recently, in fact, the Church of England has been working hard on housing. The Bishop of Chelmsford, Guli Francis-Dehqani, has the new housing brief among the bishops. The church’s council for Mission and Public Affairs has also been busy, not least with the publication of Coming Home: Christian Perspectives on Housing in 2020. What might have seemed like rather abstract wranglings among biologists, over where to put the emphasis in their theories about nature, turns out to show how right it is to be passionate about good housing (and, it turns out, about keeping abreast of biology).