Home
Đăng nhập
Đăng ký
Nội dung học
Loading...
Luyện nghe
Luyện nghe
/
Video
/
SciShow
/
Something Strange Is Happening to Raccoons
Something Strange Is Happening to Raccoons
Chọn chế độ học:
Xem phụ đề
Chọn từ
Viết lại từ
Highlight:
3000 Oxford Words
4000 IELTS Words
5000 Oxford Words
3000 Common Words
1000 TOEIC Words
5000 TOEFL Words
Phụ đề (258)
0:00
Raccoons that live near humans do pretty well for themselves.
0:04
Just think of all the garbage cans overflowing
0:06
with leftover pizza, half-eaten fruit, and scraps of pet food!
0:10
One group of researchers published a paper in 2025
0:13
that suggested that raccoons could be adapting so well to living around us
0:18
that their little faces may be showing one sign of domestication,
0:22
in the form of shorter faces.
0:24
Now, this story got around,
0:26
and you may have heard about it in passing
0:27
from someone getting way too excited about their dreams of having a raccoon as a pet.
0:32
And to be clear,
0:33
raccoons are NOT PETS and they won’t be anytime soon.
0:38
Please, I’m begging,
0:39
please do not cuddle the raccoons
0:41
But, honestly, city raccoons having stubbier snouts
0:44
isn’t what’s most scientifically interesting about this research.
0:48
See, we don’t even really understand
0:50
or agree on what domestication even is in the first place.
0:55
But studying our neighborhood trash pandas might be one way to find out.
0:59
[THEME MUSIC]
1:02
Alright, I know you may have clicked on this video because it had a thumbnail of a cute raccoon,
1:07
and you probably want to learn more about them right away.
1:10
And I promise we will get there,
1:11
but to figure out whatever may or may not be going on with these critters,
1:15
we first have to understand how scientists think about domestication.
1:19
They have… a lot of thoughts. And don’t always agree with each other.
1:24
Domesticated animals feel like one of those “you know ‘em when you see ‘em” phenomena.
1:29
And by “them,”
1:30
I mean a very fluffy cat meowing at you
1:33
because she knows that it's time to play with the laser pointer
1:37
but you're still at your little laptop and talking to people and working on scripts
1:41
and it's getting late
1:42
and she wants to play
1:43
But even though domestic cats are cute and kind of pathetic sometimes,
1:48
they also add to our lives — they can help keep mice away or be emotional support.
1:53
So researchers consider domestication to be a kind of mutualism,
1:58
which is where two species have a relationship that benefits both of them.
2:02
And it’s a little more specific than just living side-by-side.
2:06
Domestication is when one species — like humans —
2:09
increases their own survival and reproduction by somewhat controlling how another species —
2:15
like housecats — survives and reproduces.
2:18
That’s one definition, anyhow.
2:20
For our purposes, we can say that humans change domesticated species to suit our needs.
2:26
The differences between, say,
2:27
an African wildcat and a domestic cat come from thousands of years of genetic changes
2:33
that reinforce our interspecies relationship.
2:36
It’s not like raising a lion cub in your home will
2:39
suddenly flip a biological switch and make it a pet.
2:42
When researchers study domestication, they look at way more than just cats and dogs, too.
2:48
Hundreds of crop plants, like rice or potatoes, have been domesticated over time.
2:52
Farmers control the survival and reproduction of crops,
2:56
and in return we get a resource out of them: nutritious food.
3:00
The wild versions of a lot of these plants barely look like their cultivated cousins!
3:04
In any case, the specific evolutionary changes and traits that emerge
3:08
during the generations-long process of domestication are
3:12
where biologists really start splitting hairs.
3:15
We create scientific definitions based on observations and experiments.
3:20
So there’s not always a clear line between domestication and other
3:24
kinds of interspecies relationships, or even just adaptations to different environments.
3:30
A species that’s becoming domesticated over time might change
3:33
its appearance, its behavior, its nutritional content,
3:37
or any number of things that makes it more useful to the domesticator species.
3:42
This concept of a sort of checklist of traits that domesticated species
3:46
have in common is called domestication syndrome.
3:49
The English naturalist Charles Darwin was a big proponent
3:52
of the “you know it when you see it” observational sort of biology.
3:56
He actually wrote one of the early scientific books
3:59
that documented patterns in domesticated animals compared to their wild counterparts.
4:04
“The Variation of Animals and Plants Under Domestication” was published in 1868.
4:09
It was a combination of Darwin’s own thoughts and research being done by his peers.
4:13
And even though Darwin didn’t explicitly use the term “domestication syndrome”—
4:18
that credit goes to botanists in the early 1900s—
4:21
some of what he documented is still foundational to modern-day studies.
4:25
In plants, domestication syndrome could look
4:27
like changes in fruits, growth patterns, and seed dispersal –
4:31
you want the seeds to disperse less so you can collect them.
4:34
In animals, we’ve noticed things
4:36
like lighter fur, floppier ears, shorter muzzles, and curlier tails,
4:41
along with behavioral traits like tameness or differently timed reproductive cycles.
4:46
But even though these traits show up across different mammals—
4:50
like rabbits, dogs, cats, goats, and cows—
4:53
no domesticated animal has all of them.
4:56
When researching the process of domestication and domestication syndrome,
5:01
some scientists have taken an experimental approach and selectively bred animals
5:05
to try and make them more domestic across multiple generations,
5:09
usually focusing on behavior.
5:11
People also study domestication in plants.
5:14
But we’ll stick with critters for now because,
5:16
ultimately, we’re here to learn about raccoons, right?
5:19
And we’ll get back to trash pandas…
5:22
right after we keep the lights on with this quick break.
5:25
Since you love SciShow,
5:26
you’ll probably also be into this video’s sponsor: Brilliant.
5:30
Brilliant is an online learning platform made for everyone from age 10 to 110.
5:35
And they offer courses that strengthen your math skills.
5:38
As an example,
5:39
their math course on Proportional Reasoning
5:42
is designed to help you understand ratios and proportional relationships.
5:46
Over the course of 30 lessons, you’ll get to complete 357 exercises.
5:51
Which gives you an idea of just how interactive Brilliant is.
5:55
To learn for free on Brilliant for a full 30 days,
5:57
go to brilliant.org/scishow, scan the QR code onscreen,
6:02
or click on the link in the description.
6:04
Brilliant’s also given our viewers 20% off an annual Premium subscription,
6:09
which gives you unlimited daily access to everything on Brilliant.
6:14
These experimental studies can take place over the course of months or years
6:18
with fast-breeding animals like mice or rats.
6:21
Researchers can compare tamer and more aggressive individuals,
6:24
make note of differences, and keep breeding the tamer ones
6:27
to see if they can affect future generations.
6:29
The most famous research that took this approach
6:32
is the Russian Farm-Fox Experiment,
6:34
which was started by the Russian geneticist Dimitry Belyaev
6:38
and his collaborators in 1959
6:40
and has continued in the decades since—
6:42
even after his death.
6:44
Over 60 years ago, Belyaev got 30 male and 100 female silver foxes from fur farms.
6:50
These fur farms had already been breeding foxes in cages for their pelts for decades,
6:55
so they weren’t exactly wild foxes,
6:58
but they weren’t necessarily gentle lap-foxes either.
7:01
This starting population was chosen based on how friendly they were toward humans.
7:05
Belyaev and his team bred them over and over again,
7:08
and studied the next generations to see if they acted more domesticated
7:13
and what other traits appeared.
7:15
Over the years, these researchers documented similar traits in the ever-tamer foxes,
7:20
like more white spots in their coats, floppier ears, a more squat and cuter face,
7:26
and even wagging tails like domestic dogs.
7:29
So they concluded that whatever genes affected the calm,
7:32
pet-like demeanor of these silver foxes
7:35
also had effects on other developmental processes and biological traits.
7:40
And they’re still curious how much more domestic these foxes can get.
7:43
The most generous interpretation of this research
7:46
is that Belyaev and his team figured out a way
7:48
to condense the long evolutionary process of domestication
7:52
into a couple decades instead of thousands of years,
7:55
because of the really close human involvement.
7:58
Basically speedrunning what natural selection does, well, naturally.
8:03
But there have been critiques too.
8:05
In a 2019 paper,
8:06
the authors say that these experiments undoubtedly teach us about tameness in foxes
8:10
and the genetics related to behavioral changes,
8:13
but they might not actually provide evidence for domestication syndrome.
8:17
They argue that domestication syndrome is too hand-wavey of a term,
8:21
because we still don’t have a core list of traits reported in all domesticated mammals.
8:27
For example, only domestic pigs seem to have decreased brain size
8:30
relative to the rest of their bodies.
8:32
And some breeds of domestic animals have floppy ears while others don’t.
8:37
I’m telling you, my cat can airplane ear with the best of them.
8:40
In other words, domestication syndrome can be something of a hot topic.
8:45
Some scientists don’t seem to be as interested in building
8:48
a canonical list of domestication syndrome traits.
8:50
Instead, their focus seems to be on explaining the biological mechanisms
8:54
that might lead to traits we associate with domestication.
8:58
Some focus on the balance of different hormones
9:01
being produced or released at different times.
9:04
Others focus on how parasitic infections
9:06
might affect all the biological systems that are involved in domestication,
9:10
or how developmental processes might get interrupted
9:13
to make adult animals look and act more cute and baby-like.
9:17
And in 2014,
9:19
a team of scientists proposed that neural crest cells or NCCs
9:24
could be driving the physical and behavioral changes that
9:26
happen to species during domestication.
9:28
Neural crest cells form really early in
9:31
the development timeline of any animal with a backbone.
9:34
They start out forming where the backbone will be,
9:37
but migrate throughout the embryo to form different structures.
9:40
They’re a kind of stem cell,
9:42
which basically means that they’re generalists
9:44
and can become a lot of different specialized body parts.
9:47
NCCs help form parts of an animal’s head, tail, and their melanocytes—
9:52
which control the color of skin, fur, or hair.
9:54
And all those body parts also show up in domestication syndrome.
9:58
The core idea this team proposed is that domestication leads
10:01
to some sort of reduced activity of neural crest cells
10:05
Either not as many NCCs form to start with,
10:08
they don’t move as easily through the developing embryo,
10:11
or they grow slower once they actually start forming structures.
10:15
And—importantly—because NCCs are in all vertebrate species,
10:20
this idea can be tested by comparing domesticated vertebrates to wild ones.
10:24
Plus, NCCs could affect the development of different animals in different ways,
10:29
so the Neural Crest Domestication Syndrome hypothesis
10:33
could explain why there’s no one-size-fits-all domestication syndrome checklist.
10:37
So this is where that viral raccoon study comes in.
10:41
Have I kept you waiting long enough?
10:42
Raccoons are vertebrates!
10:44
So they have neural crest cells that drive their development,
10:48
just like cats and silver foxes and humans.
10:51
Some populations of raccoons have been living alongside humans for decades,
10:55
and eating our trash, bird seed, and pet food.
10:58
Fortune favors the bold, in this case the bold raccoon
11:01
who doesn’t run away from your trash can when you start yelling at it.
11:04
According to the researchers,
11:05
this could be acting as a selective pressure on the raccoons
11:08
to live more closely alongside humans.
11:11
So they could conceivably be developing adaptations
11:14
that are in line with domestication syndrome.
11:17
And, raccoons are not really being bred by humans right now.
11:20
We’re not experimentally creating domestic raccoons like Belyaev did with silver foxes,
11:26
so this possible domestication process is much slower,
11:30
like the natural selection that led to our cat and dog friends.
11:33
And even though it’s tempting to jump ten steps ahead of the researchers’ conclusion,
11:37
this paper isn’t making any claims about raccoons being domesticated!
11:41
It doesn’t say anything about a mutualistic relationship with them,
11:44
where they help us somehow and we control their survival.
11:47
This team was specifically trying to study whether urban raccoons
11:51
had one visible trait that appears on that general domestication syndrome checklist
11:55
and could be caused by NCCs.
11:58
And that trait is: a shorter snout.
12:01
So these researchers looked at 19,495 photos of North American raccoons
12:07
from the citizen science website iNaturalist,
12:10
where anyone can share pictures of the world around them.
12:12
After the team divvied up the photos
12:14
and screened them one by one to make sure that the raccoon was the correct species
12:18
and their head was clear enough to measure their snout,
12:21
they ended up selecting a mere 249 of those images for further analysis.
12:26
Based on the locations tagged on iNaturalist,
12:28
they split these images into 211 “urban” raccoons
12:32
that were snapshotted in counties with more than 20,000 people and 38 “rural” raccoons
12:38
from counties with fewer people.
12:40
Then, they got to measuring all these raccoon snouts.
12:43
And, after some data analysis,
12:44
they found that urban raccoons had 3.56% shorter snouts than their rural cousins.
12:51
Actually a little underwhelming once you get under the hood.
12:54
However, because other research involving urban foxes and mice
12:58
has also found a pattern of shorter snouts on city-dwellers,
13:01
the authors suggest that the proximity to humans could bring about this physical change
13:06
that may be linked to domestication.
13:09
But that does not, by any stretch, mean they are domesticated.
13:13
At best it’s a baby step.
13:15
And there could be other explanations.
13:17
For example, climate affects the snout length of raccoons,
13:20
and could throw a big confounding variable into the mix.
13:24
More research is definitely called for.
13:26
Understanding domestication will take a lot of time,
13:29
smart questions, and different experts—
13:32
geneticists, biologists, ecologists, anthropologists, and so on.
13:36
All the -ists!
13:38
Except physicists, I don’t think we’ll be in this
13:40
After all, we’ve lived alongside cats for thousands of years
13:43
and can’t claim to completely understand how they were domesticated.
13:47
So that’s also why the authors of that 2025 paper
13:50
suggested that other domestication researchers look a little more closely
13:54
at these trash pandas!
13:55
Even if a couple experiments have shown that tameness
13:58
is linked to the physical traits of domestication syndrome,
14:01
like a shorter snout in a couple animals,
14:04
there’s simply too much we don’t know about raccoons right now.
14:06
What we do definitely know is that raccoons
14:09
carry a ton of infectious diseases that could make you extremely sick!
14:14
So can you invite that raccoon that digs through your barbecue scraps
14:17
into your house as a pet?
14:19
No.
14:19
And will you be able to have a raccoon as a pet in the relatively near future?
14:23
Also no.
14:24
I’m sorry, but I promise…
14:26
we’re just looking out for you.
14:28
[ OUTRO MUSIC]
