You are listening to Sleeptide Science.
I'm Irie.
And I'm Haraya.
And we are Filipinos living in the UK.
Did you know dogs were the very first animal humans ever domesticated?
What?
Over 15,000 years ago, wolves and humans became friends.
And over thousands of years, those wolves slowly became the dogs we know and love today.
Hello friends and welcome back to Sleep Tight Science a bedtime show that answers your questions about science.
We love getting your questions.
They help guide what topics we cover and learn about together.
Sometimes a listener sends us a whole list of questions about one topic and it reminds us that many of you are probably wondering about the same things.
That's exactly what happened with tonight's episode.
A curious friend wrote in with wonderful questions about dogs and we thought Yes, let's explore one of the world's most loved animals together.
Dogs are everywhere in our lives.
Maybe you have one sleeping at the foot of your bed right now.
Or maybe you've seen them at the park, walking down the street or working as service dogs helping people.
They come in an amazing variety of shapes and sizes tiny chihuahuas that fit in a purse, giant Great Danes taller than most kids, fluffy Pomeranians, sleek greyhounds, wrinkly bulldogs and curly-haired poodles.
But they all share something remarkable.
They are the animal that choose to live with us, and we've been partners for over 15,000 years.
Dogs aren't like the animals in our superpower series.
They don't regenerate lost limbs like axolotls, or generate electricity like electric eels, or fly silently like barn owls.
Instead, dogs have something different.
They evolved alongside humans, learning to understand us, work with us and communicate with us in ways no other animal can.
Through thousands of years, we shaped them into hundreds of different breeds for different jobs.
Herding sheep, hunting birds, pulling sleds, finding lost people, or simply being loving companions.
And they shaped us too, teaching us about loyalty, play, and unconditional friendship.
Tonight, we'll answer three specific questions.
First, why can't puppies see when they're born?
Second, why don't poodles shed their fur like Labradors do?
And third, how can dogs wag their tails while doing many other things at the same time?
By the end of tonight, you'll understand how puppies develop, why different breeds look so different and how dogs became such amazing communicators.
A quiet thank you to Irie, 10 years old, and Hariah, who is almost seven, who live in the UK, for introducing our show.
And to Lily, eight years old, from the Sunshine Coast in Queensland Australia, for sending us such thoughtful questions about dogs.
We love hearing from you.
So get comfortable, take a gentle breath in and out.
Picture a warm puppy, curled up, sleeping paws twitching as it dreams, tongue hanging out, maybe giving a tiny sleepy tail wag.
Let's discover how dogs grow, why they look so different from each other and how they talk to us without saying a word.
When puppies are born, their eyes are completely sealed shut, and their ear canals are closed too.
For about the first two weeks of life, they're both blind and deaf.
They can't even regulate their own body temperature yet.
They need to snuggle close to their mother and litter mates to stay warm.
All they can really do is crawl slowly, search for their mother's milk, and sleep.
This might seem like a strange way to start life, but there's a good reason for it.
Puppies are what scientists call altritia, which means they're born helpless and need lots of parental care.
Not all animals are born this way.
Baby horses, for example, are precocial.
They can stand up and run within just a few hours of being born.
A foal needs to keep up with its herd right away to survive.
But puppies are born in a safe den with a mother who will care for them, so they don't need to be ready to run on day one.
Human babies are altricial too.
We're helpless for even longer than puppies.
It takes months before a baby can crawl and over a year before most can walk.
So you and puppies have something in common.
Here's the timeline of how puppies develop.
At birth, their eyes are sealed shut and their ears are closed.
Around 10 to 14 days old, their eyes begin to open, though their vision is still quite blurry at first.
By two to three weeks, their ear canals open and they can hear.
At three to four weeks.
They're walking, playing with their siblings and their baby teeth are coming in.
By eight weeks old, their senses are fully developed and they're ready to leave their mother and join a new family.
But why are they born with everything sealed shut?
It's actually protection.
Puppies' eyes are still developing, and keeping the eyelids fused together protects the delicate developing eyeballs from dirt, infection and injury.
The structures inside their ears are also still forming, and their nervous system isn't fully wired yet.
Their brains are growing rapidly during those first few weeks.
Being born helpless isn't a weakness.
It's actually a clever strategy.
The mother dog's pregnancy only lasts about 63 days, which is much shorter than it would need to be if puppies were born fully developed.
Being born earlier means a smaller birth size, which is safer for the mother.
And even though puppies are helpless at first, they're safe in the den with their mother, providing all the warmth, food and care they need.
Plus, being born with brains that aren't fully wired yet gives puppies' brains more flexibility.
Their brains continue developing after birth, wiring themselves based on the environment they're born into.
This adaptability is one reason dogs have been so successful living in so many different places with humans.
So puppies aren't born blind because something went wrong.
They're born that way, by design, as part of a development strategy that's worked for thousands of years.
Now, as those puppies grow up, different breeds develop very different looks, including very different types of fur.
All dogs have fur.
But not all dogs' coats work the same way.
The big difference comes down to how their hair grows and what type of coat they have.
Most dogs have fur that grows in two layers.
There's a soft, fluffy undercoat close to the skin that works like insulation, like wearing a cozy sweater.
Then there are longer coarser hairs on top, called guard hairs that protect from rain, snow and scratches, like wearing a raincoat over your sweater.
Dog hair grows in cycles a growth phase where the hair gets longer, a resting phase where it stops growing, and then a falling out phase where the hair dies and drops off so a new hair can grow in its place.
Labradors have what's called a double coat, a thick fluffy undercoat plus shorter guard hairs on top.
Their hair grows to a certain length, stops, and then falls out.
Labs shed heavily twice a year, in spring and fall, as they swap between thick winter coats and lighter summer coats.
But they also lose some hair year round.
The shed fur just falls off and you find it on the furniture, your clothes, and all over the floor.
Sometimes you could even see fur balls blowing in corners like tumbleweeds in the desert.
Poodles, on the other hand, have a very different coat.
They have mostly a single layer of curly hair with very little undercoat.
Here's the key difference.
Poodle hair keeps growing continuously, almost like human hair.
It doesn't have that fall out and stop phase the same way Labrador fur does.
Now, poodles do technically shed.
All dogs lose some hair, but the loose hairs don't fall on the floor.
Instead, they get trapped and tangled in all those curls.
That's why poodles need regular haircuts and brushing.
If you don't trim a poodle's coat, it just keeps growing and growing.
And all those dead hairs stay stuck in the curls, eventually forming mats.
So why did these two breeds end up so different?
The answer is selective breeding. humans choosing which dogs to breed based on traits we wanted.
Poodles were originally bred as water-retrieving dogs in Germany and France.
Their curly, dense coat protected them from cold water and didn't get heavy and matted when wet.
The coat that kept growing meant they could be trimmed in special patterns.
Shaved on the legs and body for easier swimming, but left fluffy on the chest and joints for warmth.
Over many generations of choosing poodles with the curliest, most water resistant coats, this non shedding coat type became consistent in the breed.
Labradors were bred as hunting and fishing dogs in Newfoundland, Canada.
They needed to retrieve fish and game from icy water.
Their thick double coat kept them warm and dry, even in freezing conditions.
The shedding coat meant they could naturally adjust their insulation growing thick fur for winter, then shedding it for summer.
There are many other coat types too.
Wire-haired terriers have coarse, dense fur, perfect for digging without getting scratched by roots and thorns.
Smooth-coated Chihuahuas have short fur that lies flat.
Some breeds, like the Commodore, naturally form dreadlock-like cords.
Each coat type developed because humans bred dogs for specific jobs in specific climates.
Here's the trade-off.
Shedding dogs, like Labs, lose hair naturally all over your house. but they need less grooming.
Non-shedding dogs, like poodles, don't leave fur everywhere, which can be better for people with allergies, but they need regular trips to the groomer for haircuts.
It's amazing when you think about it.
All those different breeds, over 300 recognized types, with coats ranging from hairless to corded, to curly to to straight.
All came from wolves.
Through thousands of years of selective breeding, humans created incredible diversity, all from the same ancestor.
Different coats, different sizes, different colors.
But all dogs share one special talent.
They're amazing communicators, especially with that wagging tail.
How can dogs wag their tails while doing many other things at the same time?
The simple answer is that different parts of a dog's brain and nervous system control different body parts independently.
Just like you can walk and wave at the same time, or chew gum while riding a bike, dogs can run forward while wagging their tail, sniffing with their nose and watching you with their eyes all at once.
You multitask in similar ways.
You can walk, talk, swing your arms, and think about what's for dinner all at once.
Your brain sends different signals to different body parts without you having to concentrate on each movement.
Let's look at how the tail works.
A dog's tail has anywhere from 6 to 23 small bones called vertebrae, depending on the breed.
Surrounding those bones are muscles that can move the tail up down left, right and even in circles.
These muscles are controlled by nerves connected to the dog's spinal cord, which connects to the brain.
When a dog wants to move, the brain sends different signals to different parts of the body at the same time.
Run forward goes to the leg muscles.
Wag tail goes to the tail muscles.
Sniff that interesting smell goes to the nose and head muscles.
Each signal travels along its own pathway, so all these movements can happen together without getting mixed up.
But what's really interesting is that tail wagging is often automatic.
A dog doesn't think, now I will wag my tail.
Instead, when a dog feels an emotion like happiness when you come home or nervousness when meeting a new dog, the brain automatically signals the tail to wag.
It's an unconscious response, kind of like how your heart keeps beating while you're reading, or how you smile when something makes you happy, without deciding to smile.
Tail position and wagging speed actually mean different things.
When a dog holds its tail high and wags it fast, that usually means excited, alert, and confident.
A low, slow wag means unsure or cautious.
A tail tucked under the body means scared or submissive.
Recent research has even discovered that dogs wag more to the right side when they're feeling positive emotions, like seeing a friendly person, and more to the left when they're feeling negative emotions, like seeing an unfamiliar dog.
Why do dogs wag their tails at all?
It's a communication tool.
Dogs evolved to live with humans and other dogs, and tail wagging became one of their main ways of talking without words.
Interestingly, wolves, the ancestors of dogs, wag their tails much less than domestic dogs do.
Through thousands of years of living with humans, dogs developed stronger, clearer tail communication because it helped them tell us how they were feeling.
Dogs use other body language at the same time, too.
Their ears move forward when they're alert and back when they're scared.
They pant when they're hot or stressed.
They do a play bow. front and down, rear and up, tail wagging to say, let's play.
They make eye contact to check in with you or look away to be polite to another dog.
All of this requires amazing coordination.
The dog's brain has a part called the motor cortex that handles complex movements and another part called the cerebellum that controls balance and makes movements smooth.
Multiple signals zip through the nervous system simultaneously to different body parts, and the dog coordinates everything without even thinking about it.
You do this too.
Right now, you might be lying in bed, breathing, blinking, maybe shifting position slightly, and thinking about dogs all at the same time.
Your brain is an excellent multitasker, just like a dog's brain.
But not all dogs can wag their tails the same way.
Some breeds, like Bulldogs and Boston Terriers, have very short tails or almost no tail at all.
These dogs communicate more with their whole body posture their face and their ears instead.
From helpless puppies who can't see to adults with all different coat types, to expert communicators who talk with their whole bodies, dogs show us something special about growth, diversity and connection.
Here's a wave to some of our question askers.
Jabal, age 8 in Ohio.
Teddy Simpson, age 8.
Sam Schmidt, age 9 in Heartland, Wisconsin.
Ari, age 5 from Ohio.
Mateo, age 6 from Ohio.
Harrison, 6 years old in Castle Rock, Colorado.
Nate.
Nine years old in New York City.
Jay, age eight from Hong Kong.
Orla, six years old from Macclesfield, UK.
Sienna, eight years old in England.
Bo Dibdel, 10 years old from Ebelthof, Denmark.
Grace Wallace.
Veronica, seven years old from Illinois.
Dexter Kenber. and Ezra from Michigan.
Thank you for asking questions that spark our curiosity and keep us learning.
To submit your questions.
Ask your parents to help you.
Write us a note to the email address in our episode notes.
You can also visit our website and send a message that way.
First, we learned why puppies are born blind and deaf.
They're altricial, born helpless by design.
Their sealed eyes protect developing vision and being born early with a shorter pregnancy keeps mother and puppies safe.
Those helpless weeks in the den give their brains time to grow and wire themselves to the world around them.
Second, we explored why poodles and Labradors have such different coats.
Labradors have a double coat that sheds seasonally, perfect for swimming in cold water and adjusting to the weather.
Poodles have continuously growing curly hair that tangles instead of falling out.
Bred for water retrieving without getting matted.
Different coats for different jobs, all shaped by thousands of years of humans choosing which dogs to breed.
Third, we discovered how dogs wag their tails while doing other things.
Different brain signals control different body parts at the same time, and tail wagging is often automatic, a direct expression of emotion.
Every wag tells a story.
Happy, nervous, excited, cautious.
It's one of the many ways dogs learned to communicate with us.
Dogs aren't like wild animals with one extraordinary superpower.
They're something different.
The animal that chose to live alongside humans for over 15,000 years.
We shaped them into hundreds of breeds, and they shaped us right back.
Every wagging tail, every loyal companion, every working dog.
Helping people is part of that ancient partnership.
Take a slow, deep breath in and let it out gently.
Now, picture a puppy curled up sleeping, warm and safe.
Its tiny eyelids are still sealed shut.
But soon, very soon, they'll open for the first time.
Those little paws twitch as it dreams, maybe chasing butterflies or playing with invisible friends.
Its coat, whether it will be curly or smooth, short or fluffy, is already determined by its genes.
And that little tail gives the smallest, sleepiest wag.
Another soft breath in...
Maybe tonight you'll dream of puppies opening their eyes and seeing the world for the first time, blinking at colors and shapes they've never seen before.
Maybe you'll imagine all the different dogs in the world, big and small, fluffy and sleek.
All descended from wolves, but each one unique.
Maybe you'll picture a dog's tail wagging in pure happiness.
That simple message that needs no words.
I'm so glad you're here.
Thank you for spending time with us.
From Cheryl and Clark, good night, sleep tight.
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