Today’s Wonder of the Day was inspired by Grayson from Broomfield, CO. Grayson Wonders, “Why are dogs man's best friend?” Thanks for WONDERing with us, Grayson!

We were walking past the Wonderopolis park the other day when we overheard an interesting conversation between a dog and a cat:

Dog: I don't understand it, Sylvester. I fetch the stick. I roll over. I play dead. Still they won't tell me!

Cat: Tell you what, Buster?

Dog: Who's a good boy? They ask me all the time, but never tell me who it is. It's maddening!

Cat: Do you think it's some kind of mind game these humans like to play?

Dog: It could be, I suppose. How do you deal with your humans?

Cat: I ignore them until they meet my demands and cater to my every desire.

Dog: I may have to try that. Man's best friend, my tail!

Poor Buster! We hope he eventually learns that he's the good boy. In the meantime, we hope he ignores the cat's advice and continues to do the things that make him man's best friend.

The phrase "a dog is a man's best friend" has been around a long, long time. We doubt that anyone who has ever owned a dog would argue with the truth of it. Just how did the dog come to earn that coveted title, though?

If you study the history of dogs, you wouldn't necessarily expect them to be considered man's best friend. Dogs trace their lineage back to wolves. In fact, dogs share 99% of their DNA with wolves, who are hardly warm and cuddly creatures.

Long ago, however, humans domesticated dogs. The goal wasn't to create companions or pets. Instead, dogs were primarily functional animals used for hunting and guarding property.

Over time, attitudes toward dogs began to shift. Hunting hounds became loyal friends. Guard dogs became affectionate companions. The dog became a pet that was loved regardless of what, if any, services it could provide.

Today, all you have to do is ask most any dog owner and you'll get a long list of qualities and attributes that would make any species proud. Here are just a few of the adjectives you'll hear used of dogs: loyal, understanding, kind, playful, and unconditionally loving.

When you're happy, your dog is ready to help you celebrate. On your worst day, your dog will greet you with a wag of the tail and a lick on the hand. Even when you are grumpy or mean, a dog will just look at you with love.

When it comes to animal companions, a dog really is man's best friend. They exhibit a unique blend of attributes and characteristics that other species simply do not. It's no WONDER then, that people began referring to them as a best friend. But exactly when did that start?

Historians have found several old examples of the phrase. For example, the town of Warrensburg, Missouri, claims that the phrase was born in a court case in that town in 1870. A farmer sued for damages when his dog was shot and killed. His lawyer's closing speech included the following words: "The one absolutely unselfish friend that a man can have in this selfish world, the one that never deserts him and the one that never proves ungrateful or treacherous is his dog."

The phrase is at least 50 years older than that case, though. A poem published in The New-York Literary Journal, Volume 4 in 1821 reads:

The faithful dog – why would I strive

To speak his merits, while they live

In every breast, and man's best friend

Does often at his heels attend.

Even older examples have been found from the late 1700s, including Voltaire who wrote in 1764: "It seems that nature has given the dog to man for his defense and for his pleasure. Of all the animals, it is the most faithful; it is the best friend man can have." Some even give credit to Frederick, King of Prussia, who some historians claim referred to his beloved Italian Greyhounds as his best friends.

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Don’t try to get us to change our minds about tomorrow’s Wonder of the Day. It’s already set in stone!