Ever since a wolf wandered into a human camp 15,000 years ago and settled by the fire, dogs have become an integral part of human environment. In 2013, in the U.S. alone a record $56 billion was spent on caring for dogs. What allowed these occupiers of the best spot on the sofa to make their ways so brazenly into our lives?Now we might have a clue. Although researchers say it’s almost impossible to decide whether humans actively domesticated wolves or if wolves attached themselves to human settlements, they do agree that something about the psychology of these early canids allowed the relationship to begin.And that this psychology is rooted in biological changes driven by evolution. Research shows that dogs were domesticated quicker than previously thought—that it might have taken as few as 60 generations to go from a wolf to a dog.That ease of co-habitation is also thanks to dogs possessing genes that allow them to break starch down. Wolves lack these genes. The ability to eat pieces of bread stolen from the dinner table could not have hurt these early companions as humans settled into agriculture around this time.Studies also argue that it was dogs’ agreeable personality that allowed them to fit into human world. These include cognitive abilities that allow them to be sensitive to humans and read emotional cues. This also helped by the fact that dogs retain juvenile physical characteristics of mammals like soft fur, big eyes, round shapes.And what makes dogs so popular today is that they literally come in every shape in size. There are more than 150 species of dogs alive today – a Great Dane can run up to 150 pounds while a miniature Chihuahua can weigh less than a newborn human baby at adulthood.Humans have been breeding dogs to their needs for as long as they’ve been domesticated and the needs have changed over time.…Even in the past two hundred years, certain breeds have undergone conspicuous changes.Below: the famous Balto. When Siberian Huskies were first brought to the Alaska in the early 20th century, they were puny dogs, hardly weighing more than 40 pounds. But they possessed strength and stamina that made them a hot commodity for sled racing. Then Siberian Huskies were bred to resemble wolves with their cool icy blue eyes.

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And this is how the species looks now.The daschund, which was originally bred to hunt small animals such as rabbits, badgers, and prairie dogs, are not mostly bred for dog shows and to be family pets.

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Jack Russell terrier which hadn’t changed very much in the past 100 years changed.

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Pugs have changed a lot since the English 18th century artist Thomas Gainsborough drew this pug in circa 1780. Believed to originate in China, research shows that pugs are genetically close to jack Russell terriers and that their current form – as lapdog toys—were bred in Europe. And as a result of their short form and shortened muzzle, they suffer respiratory problems and spinal defects that come from the double curled tail.

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The Great Dane

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