Close
your eyes and breathe deeply through your nose. What do you smell? Depending on
where you are while you’re reading this, the range of odors may be vast.
Sitting in your office? Perhaps you smell the ink from the copy machine or a
pot of coffee brewing down the hall. At home, as I am at this moment? Perhaps
you smell fresh laundry tumbling in the dryer or the wonderful attic smell of
an old house. If you’re sitting on the john, we’d rather not know what you’re
smelling at the moment.
Smell
is one of our most important senses, although we rarely give it much thought. When
I lived in London, my morning commute on the underground was a banquet of human
odors. The diversity of people on the subway meant a broad
swath of scents: spices, fragrances, and body odor. A veritable smorgasbord of aromas.
For
firefighters, smell is part of the toolkit. Ask any firefighter and I bet they can
describe the acrid odor of car fires, the earthy scent of a brushfire, or the
stomach churning stench of burnt flesh. The smell of the smoke at times can indicate precisely what’s burning.
So
today, in honor of our snouts, I’m paying homage to this vital link to the
world around us.
First,
let’s discuss the nuts and bolts of smell. Our noses serve as conduits for odor
molecules that are drawn into our bodies as we inhale. Those odor molecules
attach to chemoreceptors that line our noses, which, when stimulated, send
signals to our brains. The brain then interprets these signals and voilà! A
smell!
Humans
can distinguish over ten thousand different odors. Amazing! Also amazing is that each
of the hundreds of receptors lining the nose is controlled by a single gene! If
you’re missing that gene, you miss out on that particular odor. 
The
olfactory bulb – that part of the brain that transforms smell sensation into
perception – is part of the limbic system, a primitive region of the brain that
regulates behaviors related to survival. Even in our distant reptilian
relatives, the alligators, the limbic system processes smell, which allows gators
to successfully hunt and defend their territory.
But
it’s the amygdala and hippocampus, the parts of our limbic system responsible
for emotion and memory, that draw the connection between smell and memory. The
olfactory nerves run in close proximity to these vital areas, thus providing
associated links between smells and the memories they trigger.
As
our species evolved, our sense of smell would have played a crucial role in
survival. Finding food and avoiding danger are two of our most fundamental
behaviors that rely on smell. The smell of fresh dung can mean meat on the hoof.
The smell of a rotting carcass can indicate predators nearby. Our ancestors
were keen observers, as are today’s hunter/gatherers.
Even
finding a mate may be entwined in smell. The role of pheromones (chemicals
released by our bodies) in sexual attraction is still unclear, but research is
uncovering some of the strange ways scent alters behavior. 
For
example, newborns are guided to a mother’s breast by scent. It turns out the
mother’s nipples give off odorous molecules that allow the baby to home in on its food source. And here’s another nippily fact: odors given off by
breast-feeding women can actually stimulate their childless female friends, although
the exact “randy” chemical has yet to be identified (to the dismay of all you
males).
As
impressive as our sense of smell may seem, it pales in comparison to the
majority of our faunal friends. Bears have the most impressive sniffers. Black
bears have been known to hoof it eighteen miles to track down prey. Grizzlies can
smell a carcass even if it’s underwater. And male polar bears will trek a
hundred miles if they catch a whiff of a receptive cow. That’s a long way to go
for some tail…
And
here are a few other samplings from the animal kingdom: elephants can smell
water from as far away as twelve miles, even if it’s underground; snakes smell via
their tongues, catching scent molecules and processing them via specialized organs
in their mouths; and finally, the most impressive of all, the male silk moths,
who can detect as few as two pheromone particles exuded from the female from
six miles out!
Although
our noses don’t measure up to our critter counterparts, we corner the market on
smelly sexual fetishes. I present to you “eproctophilia.” Believe it or not,
there are folks out there turned on by the smell of farts. Eproctophilia is
another form of paraphilia (which we discussed last week in Dead and Lovin’ It). It’s a crazy, crazy
world out there…
Smelling
is part of our evolutionary heritage. It is hardwired into our brains and is one of
five primary senses that allows us to navigate our world (along with sight,
hearing, taste, and touch). And it’s the direct association to the emotional
centers of the brain that makes smell such a powerful trigger. Think about some
of your favorite smells. What do they remind you of? A scene from your
childhood? A long-dead relative? A favorite place? Smell can instantly
transport us to a time and place far removed from the present. So take a deep
breath and lose yourself in a memory. As for my favorite smells… a windswept beach, a wood fire at night, and bacon!!
