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[ ♪ INTRO ♪]
Picture this:
Your favorite feline
splashing around in the ocean,
diving under the waves,
taking down a southern bluefin tuna the size
of a bear…
But Wait, no!
That’s all wrong.
Mr. Whiskers fits neatly into a handbag
and prefers sunbeams over surf.
There is exactly no chance he’s taking on
a tuna.
So why does he lose his mind
when you pop open a can of Starkist?
It doesn’t make a whole lot of sense,
because cats evolved in the desert,
where there is literally no tuna.
Or any other kind of fish.
Their ancestors
were wild cats
native to north Africa and southwest Asia,
and they've likely been living alongside us
since the early Neolithic period.
Fast forward a few thousand years
to the invention of Fancy Feast,
and the arrangement
is working out pretty well.
But there’s no denying
that most cats
would choose a stinky can of tuna
over the dozens of available
Fancy Feast flavors.
Cats –
and humans, too –
enjoy certain foods because of the umami.
Umami is the word
that describes savory, meaty flavors.
In both cats and humans,
the ability to taste umami
has to do with two proteins
called Tas1r1 and Tas1r3.
In humans,
these two molecules form a receptor
that detects the amino acids
glutamic acid and aspartic acid,
which make your brain say “umami.”
Amino acids are the components
that make up protein,
so it makes sense for them
to taste good.
That’s valuable energy right there!
In fact, glutamic acid
is the stuff in food additive MSG –
it’s basically pure umami flavor.
Nucleic acids also play a role,
acting as flavor enhancers.
When you hear the term “nucleic acid,”
you might think of DNA and RNA.
Those are the most familiar types
of nucleic acids,
but there are also a variety of nucleic acids
present in all kinds of biological tissue
– including food.
These compounds help
give food its flavor.
But in cats,
the ability to taste umami
works sort of opposite
to the way it works in humans.
They’re tasting an almost
totally different umami
to what we taste.
In a 2023 study, researchers
used computer modeling of protein structure
as well as cell line studies of cat taste
receptors
to help suss this out.
And before you accuse them of taking
their research too seriously,
they also did cat taste tests.
This helped them figure out what molecules
in food
were the primary drivers of whether a cat
thinks something tastes good.
In cats, the Tas1 receptor pair
is not activated by just amino acids.
Instead,
it’s activated by certain nucleic acids
and enhanced by amino acids.
A nucleic acid
called inosine monophosphate,
or IMP, is
enhanced by a number
of different amino acids,
including one called histidine.
And for cats, the IMP
and histidine combo
is a powerful flavor combination.
really takes them to flavor town.
Tuna just happens to contain a lot of IMP
and a lot of histidine.
In fact, it has more IMP
than any other nucleotide,
and more histidine
than any other free amino acid.
So, that does explain
why Mr. Whiskers begs for
your tuna salad sandwich
even though he’s not ever going to
singlehandedly land a bluefin.
Other types of fish also
contain these components,
but not as much of them.
Even rat meat,
a more likely prey item for cats,
is pretty low in histidine.
And meats like
chicken, beef, and pork
don’t seem to have any free histidine at
all.
The good news is,
cats also like other combinations
of amino acids and nucleic acids.
So they’re not going
to come for you in your sleep
if you put something else in their bowl.
I mean, Probably.
So why would cats evolve
to prefer something that lives
thousands of miles from their homeland
in an environment
they could never physically enter?
Well that’s…
not super clear.
A researcher who was not involved
with the study speculated
that cats who hung around
fishing ports eating scraps long, long ago
might have had an advantage
over the ones who still had
to catch mice like a bunch of suckers.
And there’s evidence that domesticated cats
were eating fish thousands of years ago,
so it’s not like this
is a super recent development.
So your kitty’s food preferences
basically have more
to do with the interactions
between amino acids and nucleic acids
than with what their wild ancestors ate,
or even what’s good for them.
Which is why we should note
that not only is tuna
not natural prey for cats,
it’s also not especially healthy.
Neither raw nor canned tuna
are nutritionally complete,
so tuna should be a treat,
not a main meal.
And even though you might never get
to see Mr. Whiskers
pull humongous fish out of the ocean,
maybe it’s enough
to know that he totally wants to.
And it won’t hurt
to give him a spoonful of the stuff
every now and then.
That way you can both pretend.
Now If you enjoyed this fun,
lively story
about the science of cats and thought
“Man, my kids slash students
slash nieces and nephews
would love this if it was just written
on a second grade level
with some educational standards
thrown in,”
ok, And you might say
“Stefan, that’s very specific”
but also I have good news for you.
Because we have a whole channel
just for kids,
and we have an episode
where Squeaks the robot rat
learns about why cats have whiskers,
Which you can find a link to
in the description.
SciShow Kids
is written with
early-grade Next Generation Science Standards
in mind to help kids grasp
age-appropriate ideas.
And it’s also just a ton of fun.
So send the young curious mind
in your life
to youtube.com/scishowkids,
and thanks for joining us today.
[ ♪ OUTRO ♪ ]
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