CNN  — 

“Fur babies.” Dogs on planes. Dogs in purses. Dogs in restaurants. Dogs, dogs, dogs.

Man’s best friend is now in every part of our daily – and nightly – lives. It’s a relationship that goes back 20,000 years.

Yes, you read that right. 20,000(!) years. Dogs were the first thing that man ever domesticated, the first way that we adapted our environment to us – and that fact changed, well, everything.

“I think one thing that you could very safely say is dogs made our lives a lot easier,” David Grimm, an editor at Science magazine, told me for my podcast “Downside Up.”

“Again, we are living hand to mouth. We are living in very cold conditions often. We are maybe not eating for days at a time. There are all sorts of creatures attacking us. Having a dog helps us survive,” he added.

There’s even one theory – put forward by author Pat Shipman – that the reason Homo sapiens outlasted Neanderthals in the evolutionary battle is because we had domesticated dogs and they, well, hadn’t.

What we know for sure is that all modern dogs are descended from the gray wolf. And that, most likely, packs of these wolves followed early humans – a nomadic people – around, hoping to dine on the scraps and refuse they produced. Eventually, as the theory goes, a few dogs got close enough to humans to grow somewhat tame. And humans realized the utility of having an animal around – for safety, hunting and the like.

But as the wolf became the dog, the relationship went from a utilitarian one to a much more intimate one.

In an excavation of a 12,000-year old village in ancient Israel, for example, a woman was found buried with a puppy – a sign that even that long ago, dogs meant more to humans than just what they could do for us.

Fast forward to the late 1800s, when something else happened that changed our relationship with dogs: flea and tick shampoo was developed.

Prior to that innovation, dogs were purely outside animals – they were considered too dirty to be allowed to spend any time inside. No longer.

“Once this animal sort of crosses the threshold from being outside inside, in my mind, he’s no longer an animal anymore,” said Grimm. “He starts to go down this road of a member of the family because now your dog is sleeping on your couch. He’s sleeping with your kids. He’s sleeping with you. You see him every morning when you get up. He is literally part of the household. And I think this is a really fundamental transformation where you go from dog as pet or even companion to becoming a member of the family.”

And once dogs got into our houses, they changed us as much as we changed them.

“[The dog] sits right on that border: one leg in the animal world, one leg in the human world, the world of culture,” Dr. Margo DeMello, an anthrozoologist at Carroll College, told me. “In some ways, the dog has lost a lot of its animalness and gained some humanness, but that is also transferred to us. Our lives are richer, and our lives are different because of this relationship and because of this intimacy that we have.”