The Story Behind Man's Best Friend

There are around 400 million dogs in the world, the majority of which are pets. While the animals know a surprisingly large amount about their human companions, there’s plenty we still don’t know about them. In celebration of National Dog Week, here’s all kinds of information that you probably never knew about your best friend.

A Brief History of Inter-Species Love

While the exact time that humans and dogs started to socialize together is unknown, most researchers agree that the pairing occurred at least 15,000 years ago. There is evidence dogs were domesticated by 12,000 BC, as archaeologists have discovered an Israeli grave site from this time period where an old man had been buried with a puppy.

While early researchers argued whether dogs were most closely related to coyotes, dingoes or wolves, DNA evidence has proven conclusively that our four-legged friends are most closely related to gray wolves. The means that the animals became domesticated is contested, but one common theory says that wolves started to scavenge around human campsites where they could get meals with minimal effort and that wolves that were less frightened by humans soon saw an advantage in aligning themselves with paleolithic man.

Image courtesy of Sometimesong's Flickr stream.

In the beginning, both species would gain significant benefits from one another.

Dogs would be safer, have a more reliable food source and benefit from humans' ability to see predators and prey from a long distance. Humans would benefit as dogs increased sanitation by cleaning waste and food scraps; dogs also would have used their excellent hearing to warn humans of approaching animals. On the hunt, dogs would be able to use their strong sense of smell to track prey, as man used his tools to bring down large animals with less effort. Both species would also benefit from the increased body warmth during cold nights. It is very likely that humans not only shaped the future of dogs, but that dogs changed our evolutionary course as well.

Selective breeding allowed certain dogs to excel at certain tasks, such as herding, ratting, hunting or carrying weight. The idea of pets solely for the sake of companionship wasn’t such a major part of the average person’s life until the suburbanization of Western culture after World War II. While dog training existed long before this, the idea of breaking the animals of their natural digging, barking and jumping instincts only really took off after this point and it seems we may be on the cusp of a new evolutionary mark for dogs as they are increasingly bred for companionship skills rather than working skills.

Image courtesy of nyominx's Flickr stream.

Cross-Species Benefits

Dogs can even be used to detect oncoming conditions such as cancer. When a control group of dogs were trained to smell out lung or breast cancer in the breath of test subjects, their accuracy stayed between 88 and 97 percent. It sure is a whole lot less invasive than a biopsy.

People who own pets, whether dogs or cats, have been shown to be healthier and happier than those who do not own an animal. In fact, one study showed pet owners had a major reduction in minor health problems during their first month of ownership and dog owners continued to show these improvements through the duration of the study.

Image courtesy of Martin Kuo's Flickr stream.

What’s Breed Got To Do With It?

Dogs have more variations in size, appearance and behavior than any other animal on earth because they have been targets of artificial selection through human interference, rather than natural selection. Scientists have even recognized 155 distinct genetic locations that account for all of these differences.

Dog sizes vary from the world’s smallest dog, a 2.5 inch tall Yorkshire Terrier that weighed 4 ounces, to the world’s tallest dog, a Great Dane that stands at 43 inches (that's him above), to the 343 pound English Mastif that was named the world’s largest dog. Similarly, dog lifespans, which are around 11 years on average, vary greatly by breed. In fact, the Dogue de Bordeaux has a notably short lifespan that averages just over five years. Many other breeds, including Toy Poodles, Japanese Spitz and others have an average lifespan of fourteen and a half years. Strikingly, the world’s oldest dog, an Australian Cattle Dog named Bluey, lived to be almost 30.

Breeding can also affect the level of energy and muscle a particular dog has. Some of the best athletic dogs are the Siberian Huskies used in the Iditarod sled race. Scientists fount that these animals burned 11,000 calories the day, which is eight times the proportional calories burned by a Tour de France cyclist. They also take in three times the oxygen of human athletes.

Another famed animal athlete is the Greyhound, which is one of the fastest accelerating animals in the world, second only to the cheetah. Greyhounds have an incredible heart, the same size as a human, but that beats at twice the speed of a human when exercising.

Startling K-9 Psychology

While people like to think we have more in common with our primate ancestors than any other animal, when it comes to communication and social dynamics, we actually have more in common with dogs. Researchers have said that while dogs are only as smart as two-year old humans, they have the social skills of teenagers. In fact, dogs are the only animals that understand pointing. They understand human languages better than other primates and the average dog can be taught as many as 165 words, more than an ape can learn. Particularly smart dogs have even been taught over 300 words.

Dogs understand deception, which chimps cannot grasp as clearly. Researchers tested this by placing two covered buckets, one with a treat and one without, in front of the dog. Half of the dogs would be directed to the wrong bucket by a person in the room, while the others would be given correct signals. While all of the dogs would start out listening to the human, those that were being lied to soon started going to the opposite bucket.

Dogs also know how to deceive humans without getting caught. To test this, dogs were left in a room with two containers with bells, one of which was muted and one of which was not. Researchers observed that when the animals were being watched, they would go to either of the containers, but when the observer looked away, the animals would always go for the quiet container.

Image courtesy of srte's Flickr stream.

I learned my dog is the jealous type when I came home and greeted my roommate’s dog before him. He immediately tried to fight her. Apparently, I was on to something here, because Vienna researchers studied whether dogs can get jealous of one another a little while ago by rewarding one dog with a treat for doing a trick and then asking the other to do the trick without a reward. The unrewarded dog soon got annoyed and stopped performing the trick, which did not happen when the same animal went unrewarded without another dog around. Up until that time, primates were the only animals known to show signs of jealousy.

Do you have a dog? Share your favorite stories about his or her behavior in the comments.