Extensive genetic analyses has verified that the domestic dog is derived from gray wolves only, but the immense diversity in dogs is due to selective breeding for desirable traits, be they behavioral or physical. Once domesticated, today’s domestic dog spread around the Old World and eventually became ubiquitous in the New World.
Early domestic dog characteristics may have been the result of selection pressures associated with the human transition from hunter gatherer to nomadic herding to sedentary agricultural lifestyles.
For millennia as humans changed, so did their dogs. During this period, natural dog breeds developed based solely upon the human influence and the environments in which they lived. Eventually, humans began more selective breeding to create dogs with specific helpful behaviors, such as barking to warn of potential danger or unfamiliar people, fighting in war alongside their humans, herding and guarding livestock, scent tracking and retrieving game, and for rodent control. Selective breeding emphasized desirable characteristics and traits giving rise to modern domestic dogs.
The Victorian era (1837 – 1901) saw a further escalation of selective breeding to create specific breed types identifiable by coloring, size, haircoat, and behavior traits and characteristics. The American Kennel Club (founded in 1884) and The Kennel Club in the UK (founded in 1873) were formed to establish registries for these accepted “pure breeds.” Today over 350 registered pure breeds exist, although there are many types of dogs that are not recognized by the AKC or Kennel Club.
In addition to these pure breeds, there are now hundreds of “designer” and “hybrid” dogs resulting from the selective crossing of the known pure breeds. The American Canine Hybrid Club and The International Designer Canine Registry were created to catalog them.
Then there is the mongrel or “mixed-breed” dog of unknown pedigree; often the result of uncontrolled mating. Even these dogs are loved and have their own clubs, such as the Mixed Breed Dog Clubs of America and the North American Mixed Breed Registry.
Despite all their differences and no matter their heritage, man’s best friend is a mirror of man’s best (loyalty, steadfastness, strong work ethic) and worst (aggression, anxiety and neurosis) qualities. All dogs—no matter what their breed—share a common body language that speaks to both fellow dogs and observant humans. All dogs can learn an astounding number of human language words and are skilled at recognizing other human cues—both body language and vocal tone. The fact is dogs too often understand their human owners better than the human understands them.