Dogs and humans have been close companions since well before the advent of the written word, and in that time, the relationship has taken some surprising turns.

The Dog-Human Relationship is Old

Scientists are still debating exactly how long dogs and humans have been friends, but research suggests it dates back at least 32,000 years. That's given dogs of people plenty of time to develop a strong affinity for one another. The ancient Egyptians buried revered dogs like kings, in tombs filled with valuable goods. When a pet died, the owners shaved off their eyebrows as a show of grief.

Dog's Noses Are Magic

You already know that your dog can smell things you don't even notice, but dogs' sense of smell is so good that it's like magic to humans. Dogs have more cells dedicated to scent, and they also move their noses in the direction of something that piques their interest. The result is a sense of smell that's between 10,000 and 100,000 times more accurate than our own. No wonder your dog wants just one more chance to sniff the mailbox.

Your Dog Isn't Colorblind

If you think your dog can't tell that you've changed your hair color, think again. For animals driven by their noses, sight is less important than scent. Dogs hunt at night, which means that sharp night vision is more important than recognizing daytime colors. Dogs can see plenty of colors. It's just that their range is more limited than our own. Dogs don't have green or red color receptors, which means they see most objects in shades of yellow and blue.

Your Dog is Pretty Good at Self-Control

You might shake your head when your dog dashes out the door chasing a squirrel or bites his best friend a little harder than he meant to. Dogs are masters of self-control, and being raised with siblings is key for developing inhibitions. When dogs bite too hard or engage in other annoying behaviors, their siblings yell, squeak, or shun them, helping Fido learn how to behave. By the time they're adults, the average dog's mouth can exert about 200 pounds of pressure per square inch. Even if your dog does nip at you, he's controlling his bite. Word to the wise: dogs learn this self-control primarily from their siblings, so taking a dog away from their litter too early makes for a poorly behaved dog.

Your Dog Knows You Better Than Any Other Animal

Most scientists now agree that dogs and humans co-evolved. This means that both species adapted in ways that tightened their relationship with one another. One of the most interesting ways this manifests in dogs is in their ability to read human body language. To most animals, a human smile looks a lot like a tooth baring snarl. And when dogs “smile,” they're showing either anxiety or aggression. But when humans smile at dogs, dogs recognize it for the welcoming gesture it is and often respond with a tail wag and a smile of their own. Your canine companion can read your body language better than any other animal—even our closest relative, the chimpanzee.