How Dogs Coevolved with Humans

[Narrator] Dogs are our companions,

but they're also living proof of artificial selection.

Dogs have a unique relationship with humans.

They have co-evolved and have adapted to live

in our human-like world around us.

They descended from a gray wolf-like ancestor,

and they are one of the first animals,

if not the first animal, to have been domesticated.

In the last 30 or so years, we've seen a huge boom

when it comes to studying dog cognition and dog behavior.

[Narrator] This is Dr. Byosiere,

a dog cognition researcher.

Let's have her walk through some key

K-9 communication behaviors you can observe at home

that demonstrate our unique co-evolution with dogs.

Wendy.

Wendy!

Oh, can I give you both snacks?

This movement that you see in your dog's eyes

when they look at you, when they gaze up,

staring at you lovingly, wanting snacks,

we call it puppy dog eyes.

But, in fact, this is the eye musculature that we see

more defined in the dogs we have in our homes.

And particularly we see this through the levator muscles

that they have, located just around their eyes.

It gives them more control, in a sense,

over how they move their eyes.

So we can be very expressive in how we move our eyebrows,

just using them in conversation, lifting them up.

And these muscles that are more present

in our dogs that we have at home,

it allows them to wiggle those little

spotty, dotty, hairy bits that they have

right above their eyebrows,

potentially making them more expressly communicative,

or potentially just making them

a little bit more manipulative to get more snacks.

[Narrator] A 2019 study compared

these upper eyelid muscles, and found

that they were much more prominent in dogs

than in wolves, except the Siberian Husky,

which is more closely related to wolves.

[Dr. Byosiere] When you look at huskies and malamutes,

that musculature is less defined,

and actually more similar to what you see

in wolves, where those muscles are hardly present.

[Narrator] So basically we bred big, cute puppy eyes

into modern canines?

As humans, our attention is drawn towards the eyes,

and so we like dogs that have large eyes.

[Narrator] Another clear example

of our co-evolution with dogs is at they seem to understand

what we mean when we point to something.

Research currently suggests that dogs outperform

every other living species on the human given pointing task.

Two choice object discrimination task

is typically what's done to evaluate

pointing comprehension in dogs.

And you can actually try this at home with your own dog.

The idea is that you have two can containers,

both of which have treats taped on the inside.

So they smell equally like food.

However, one of them will have an additional treat

on the inside for the dog to obtain.

Human experimenter will sit directly in front of a dog,

and give a gesture.

Then you let the dog make a choice.

The one with the snack that you've pointed to,

or they can pick the other one.

Andy!

Good job!

[Narrator] So is this something

that dogs have learned from us,

or has pointing been selected into them

by living alongside us for thousands of years?

Wolves potentially would not have a need, per se,

to follow the human given pointing skill.

Their environment may not consist of a human.

They may actually be more fearful towards humans.

And so the world in which dogs live

really is a human focused one.

If we as humans use it to communicate

with one another, dogs that live alongside us

could also benefit from understanding certain behaviors.

Wendy!

Good job.

[electronic music]

Eye contact is extremely important in humans.

It's where we automatically first look

when we look at other individuals,

and the eyes are extremely communicative.

And this is something that is unique

in the sense that many animals don't expressly like

making eye contact.

However, if you were to try to sit at home

and look at your dog, and stare lovingly into their eyes,

odds are is that they'll look back at you.

So we have a very cool feature,

which is that our whites around our eyes,

known as the sclera, they are white.

And this means that when you look from side to side,

that you can start to identify

things like where an individual is looking.

This can be really important for communication,

and it's actually something that dogs

have seemingly picked up on.

[Narrator] One way to show this clearly

is the impossible task experiment.

You have a Tupperware container filled with a toy,

and you don't lock the lid on the Tupperware container

in place.

Let your dog explore, have them sniff it out,

check it out, and obtain whatever reward

you've placed in there.

You keep doing this a couple of times, just to make sure

that they can get the snack,

and that the reward is solvable.

However, when it comes to the test trial

in the unsolvable paradigm, the idea is that

you lock the Tupperware lid in place

so that the reward is no longer accessible.

And you let the dog go, and you try to see what do they do.

And what happens with a lot of dogs is that

they actually sit down and will wait for someone

to help them out, and will make eye contact

with someone who's available to make eye contact.

[Narrator] Researchers have long documented

that dogs understand when a human

is focusing their attention on them.

You can try this at home.

You can grab a snack, place it in front of you

with your dog directly across.

Ask them to wait.

Leave it.

Stare at them, see what they'll do.

Give them about 10 seconds, I would say,

and see if they approach you.

And if they don't, let them come and eat the snack.

Okay.

Then I would do this again.

Put the snack on the ground,

but turn around and give them another 10 seconds,

and see if they actually eat the snack.

Sneak!

[Narrator] So dogs pay attention to human attention.

They're aware when we stare at them.

They might even enjoy it,

thanks to the love hormones we both share.

When Wendy here takes a look into my eyes,

what ends up happening is that

we both have increases in love hormones,

like oxytocin and dopamine and prolactin,

which you actually see in the maternal bonds.

Humans have an increase as well

when we stare into our dog's eyes.

Dogs also have an increase in these love hormones as well.

[Narrator] And how do we know this?

You look at saliva samples.

So you have humans and dogs chew on various objects

before and after interacting with one another.

And you evaluate differences in the types of hormones

that are present in their systems.

When we interact in certain ways,

like petting or hanging out,

you see increased dopamine and oxytocin love hormones,

which means that it makes us feel good as humans

and it also makes dogs feel good.

[Narrator] Humans and dogs speak to each other

with their voices and their barks, respectively.

But a 2007 dog cognition experiment in Hungary revealed.

There are six types of barks that humans can identify.

When a dog is scared or fearful.

[dog barking]

Another one was an excited bark

while an individual was playing with the dog.

[dog barking] Something's going on

in the neighborhood.

[dog barking]

Where dogs are left alone.

[dog barking]

But there could be more barks.

It could be that certain dog barks

are intended for human understanding.

[cat meowing] Cats meow,

not to talk to other cats,

but essentially to talk to humans.

Wolves are more likely to howl in a certain way,

and are less likely to bark.

And so it could be that that barking that you hear at home

is actually something that is really intended

for you as the owner.

[Narrator] Working dogs like police dogs

and seeing eye dogs have all been trained,

and seem to excel in language.

But even your average layabout

could have a vocabulary of dozens,

potentially hundreds of words.

Sit.

Good boy.

Most dogs are familiar with the words

that are relevant to them,

and the words that are important to them.

Sadie, where's your duck?

Okay.

Good job.

And so there's a great study that looked at something

called the Cocktail Phenomenon.

Wendy!

Hi.

Hi.

So when you call over Wendy in a crowded room,

the idea is that Wendy also pays attention.

Just like if someone were to call my name in a crowded room,

my interest is piqued, and I peek up just like Wendy does

when she hears her name in a crowded area.

[Narrator] So what about these TikTok dogs,

like Stella or Bunny, who seem to string together

human speech by pressing a specially designed voice pad?

There's this big trend right now

where we have dogs that have learned to push buttons

that have a voice recording of the owner

associated with them.

[Woman] Go.

Poop.

But did she actually poop outside or something?

Like you were saying, it would just be nice to

have a bit more context to these

just so we know what comes before and what comes after.

When they string words together,

I don't think we have enough evidence right now

to say that they're understanding

the grammar and the syntax that's associated with

what those words mean.

However, this could be something that,

over time, we learn is actually what they're doing.

[Narrator] So are we as humans with our breeding practices

artificially selecting for dogs with certain traits,

or is this something that they're able to learn easily

in very early stages of life,

and throughout their individual lifetimes?

There could have been genetic predispositions

for many of these things that we then, also,

indirectly selected for,

or maybe even directly selected for,

and that have inadvertently resulted in dogs

who are really successful at learning quickly.

So it could, in fact, be that it is not

nature versus nurture, that it is a combination

of all of the above.

Dogs are really going that extra mile

when it comes to communicating with humans,

when it comes to understanding our body language,

fitting into our mold of what we want them to be,

living in the cities.

Dogs really have to put up with a lot

when it comes to living with humans.

And one of the things that's quite remarkable

is the fact that dogs can understand and identify

thousands of words, and we as humans

can only potentially identify six barks.

And so this discrepancy shows that we as humans

actually have a lot of learning that we could do

if we want to stand up to what our dogs are actually capable

of understanding when it comes to us.