You've probably heard that lots of mammals besides humans have incredible senses of smell,
like how dogs use their noses to track down food or communicate with each other or find
drugs.
But think about it.
The smell of your mom's cooking or your childhood home sometimes sets off powerful
memories, doesn't it?
And you can tell right away if food goes bad.
A review published last week in the journal Science argues that humans do stack up to
other mammals in the smell department, although we detect different scents for different reasons.
So why do we think our noses suck?
Well, this researcher suggests that it's because of misconceptions that started with
a 19th century neuroanatomist named Paul Broca.
Your ability to smell comes from two ovals of tissue tucked under the frontal lobe called
the olfactory bulbs, which receive smell information and send it on to the rest of your brain for
interpretation.
In many mammals, like dogs, these bulbs sit right at the front of the skull and are big
compared to the rest of their brains — in mice, for instance, they make up about 2 percent
of total brain volume.
But in humans and other primates, they're kind of pushed out of the way and small by
comparison — they only account for about 0.01 percent of your brain volume.
So while investigating the anatomy of the frontal lobe, Paul Broca thought our relatively
tiny bulbs meant that our behaviors are guided by other brain regions and thought processes,
instead of smell like many other mammals.
This recent review suggests that, like a game of historical telephone, this idea got passed
around until a general scientific understanding was that humans have a bad sense of smell.
But, turns out, it might not be that simple, according to experimental data.
In some studies, scientists compared the number of neurons in olfactory bulbs of lots of mammals,
because we think information processing has to do with the number of neurons and connections
between them, not just brain size.
And humans were right up there with animals like mice, rats, and monkeys.
Other studies showed that humans are just as good or better than other mammals at detecting
tiny amounts of certain scents, like some sulfur-containing compounds or the smell of
bananas.
But we're also worse than mice, dogs, or rabbits when it comes to other odors.
One 2007 paper in Nature Neuroscience even found that humans can follow scent trails
like dogs.
They compared a dog following a trail of a pheasant dragged through a field to a human
sniffing for chocolate essential oil, and their paths were similar!
This is a hilarious thought to me that there's just a guy sniffing through a field after
chocolate smell!
But even with all this research, the review suggests that we still have a lot to learn.
It can be hard to compare our sense of smell with other mammals because we experience scents
differently.
Like, we don't go around sniffing each other's butts because we have other means of communication.
Basically, smell is definitely part of our social makeup and things like memory, but
I don't think we're going to see luggage-sniffing humans at airports any time soon.
In fact, researchers are doing just fine making discoveries with their other senses, like
sight!
In February, a group of scientists and rock climbers teamed up on a three month expedition
to the tallest volcanic stack in the world, and found an extremely rare stick insect.
And this discovery, along with others, is helping us preserve little nooks of biodiversity!
At the end of last year, we did a list show about some creatures that are endemic, meaning
they're only found in one place.
On that list was a creature called the Lord Howe Island Stick Insect, commonly known as
a Tree Lobster because… well… it's huge and sometimes-reddish and, y'know, could
be confused for a crustacean.
Tree lobsters were thought to be hunted to extinction by rats in the 1920s.
But that changed in the early 2000s when rock climbers stumbled across a handful of them
under a bush on a steep volcanic rock formation called Ball's Pyramid.
Ball's Pyramid is about halfway between Australia and New Zealand, just south of Lord
Howe Island.
Both islands are home to lots of endemic species, and are on the UNESCO World Heritage list.
Since 2003, the Melbourne Zoo has been breeding these stick insects, to hopefully have enough
to reintroduce them onto Lord Howe Island someday.
After they kill all of the rats, I guess.
They have thousands now, but they started with only two insects.
So scientists have been concerned about genetic diversity and their ability to adapt to their
environment when they're released back into the wild.
So, back in February, scientists from the Australian Museum Research Institute traveled
to the islands to survey the fauna there, and teamed up with some rock climbers to search
for another female tree lobster.
They found 10, and collected one!
They named her Vanessa after the climber that spotted her, and she's now safely back at
the zoo making babies.
But the discoveries didn't end there.
The research team also came back with some tissue samples from another endemic species,
this time a bird, to add to the museum's collection of over 80,000 frozen samples so
scientists can look at their genomes later.
And they observed a beetle that was thought to be extinct because it hadn't been seen
in 140 years!
These researchers hope that the results of their survey, and more to come, will help
us continue to find better ways to protect the unique biodiversity of these islands.
Thanks for watching this episode of SciShow News, which was brought to you by our President
of Space, SR Foxley.
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