Have you ever been sitting on a bumpy, crowded bus
full of mysterious smells?
And wondered to yourself, why do we even smell
things in the first place?
What makes something smell really good or bad?
Let's find out on today's episode of Colossal Questions.
Smells are nothing more than teeny-tiny little particles,
floating in the air around us that we suck up
through our nostrils.
That odor-filled air heads right up
your nasal passages in your nose where the odor molecules are
finally trapped by a thin bit of tissue
called olfactory epithelium.
These special nerve cells are covered
in cilia, which are like tiny hairs that
stick out and trap the smell particles as they float past.
The cells then send a signal directly to your brain,
telling it what different smells are entering your nose.
Most pungent odors, both nice and nasty,
tend to be made up of lots of different odor molecules
that mix together to create the distinct smell we recognize.
Every single time you breathe in through your nose,
the olfactory epithelium is alerted.
And the process starts again, over and over, all day long.
Most of the time, whether or not,
we think something smells comes down to memory.
Our brains are great at remembering certain smells
and associating them with good or bad memories.
For instance, your absolute favorite meal
might smell mouthwatering to you, but stinky to someone else
who's never tried it before.
That's why there's so many smells out there
that some people love and others can't stand.
OK, so most of the time, our memories
help us decide if something smells good or bad,
but what about the rest of the time?
Why are there some smells that seem to automatically make us
gag?
Well, it just comes down to pure instinct.
Take blood for example, both the sight and the smell of blood
is well known to repel animals who are prey like deer,
rabbits, and yeah, humans.
Even if you've never smelled blood before,
it's likely to make you squeamish right away.
But to predatory animals like wolves or tigers,
blood smells tasty.
So we tend to steer clear of places
that smell bloody and might be full of predators.
There's other more obvious examples too, like poop.
It's super unhealthy to touch poop, so our sense of smell
tells us from day one to stay clear.
The same is true for lots of things
that might get you sick, too, like rotting food,
for instance.
That rotting smell is really just the smell
of dangerous bacteria, breaking down the cells of the food
and releasing an icky chemical called hydrogen sulfide.
This toxic stench smells so bad that it
makes you want to stay far away, making
the stink of our old, unhealthy food
bad enough that you'd never consider eating it
even if you don't have the memories to back it up.
So when someone tells you to just trust your instincts,
you can confidently tell them that you already do.
Just don't expect them to know what you're talking about.
[music playing]