we take for granted.

But, how does having one affect us?

(upbeat music)

- My name is Meg Olmert and I'm the author of

"Made For Each Other: the biology of the human-animal bond."

Our journey with dogs began about 45,000 years ago

according to the latest archeological evidence.

It preceded many hundreds of thousands of years

with a more casual, and perhaps distant, pragmatic

relationship with wolves as well.

But about 45,000 years ago we start to see the bones change

and indications that A, dogs are certainly living with us.

And that living with us appears to have had certain

effects on their biology and their physiology.

That is what enabled them to

become our best friends.

- [Narrator] How does this relationship work?

- There is a feedback system that both neurochemically

and psychologically and behaviorally

that sets up between you and your pet.

And how good you are to your pet

is often exactly reflected back.

Although, what I would say

is they tend to be wildly generous.

More generous than we are.

So, that is why, you know, they'll be wagging their tail,

you know, thrilled to see you when you come home

or if it's a cat it's purring.

And you may be very distracted but they aren't.

You are the greatest thing they ever saw

if you've developed this relationship.

If you've earned it.

You have a different relationship with your own pet

versus your, even your neighbor's pet, because it's,

that's your closer family.

It's a different kind of bond and when they do FMRI studies

just like a mother will have certain brain regions

light up very strongly in the dopamine

and oxytocin rich areas when they look at a picture

of their baby versus just another infant.

When you look at a picture of your dog versus another dog,

you see the same thing.

If you love dogs you're gonna get this reward

to a degree whether you are looking at your dog or not.

Do therapy dogs work?

Well they certainly can.

Dogs can do amazing things.

With our program Warrior Canine Connection

we work with service members

and veterans with post-traumatic stress disorder.

We have the patients who say, "This dog

is better than any drug I ever took.

I didn't sleep for five years until this dog

slept next to me."

- [Narrator] What happens to your body

when you're with your dog?

- [Meg] Your heart rate comes down,

your blood pressure comes down,

your heart rate variability which is the ability

of the heart to duck and dive

and respond to stress improves.

You release oxytocin, the opioids,

adrenaline, and serotonin.

So, all of these great reward chemicals

and anti-stress chemicals can be released

in both you and the pet.

- [Narrator] What is oxytocin?

- Oxytocin is a very ancient chemical.

It's in all social mammals.

There's variations on it that you find in birds

and in turtles, and in worms.

And it most effectively is known for releasing breast milk

and creating labor contractions.

That's what it was first known for.

So in a sense, it is the quintessential mammalian hormone

since live birth and production of breast milk identifies us

as mammals and mammary glands, et cetera.

About 25 years ago they discovered that besides the oxytocin

receptors and cells in the body that are producing oxytocin

in the breast and the uterus, lo and behold,

it's produced throughout the brain and in all the areas

that control behavior and emotion.

So what was it doing there?

And what they discovered was that it was talking to other

classic brain neurotransmitters such as serotonin,

and dopamine and adrenaline, and the opioid system.

And it was setting up, by doing that, this perfect

mental physiologic state of calm.

It is the most powerful drive and it creates the bond

that lasts a lifetime.

That's how strong it is.

(happy music)