There are an estimated 500 million domestic dogs worldwide, and all of them are related. At the base of their evolutionary tree stands the gray wolf, from which every type and breed of dog has descended. As geneticists have discovered, in terms of DNA, the difference between wolf and dog is infinitesimal. While natural selection has produced some of the changes that make one type of dog different from another, the effect of human influence has been far greater. It could be said that of the hundreds of modern dogs known today, all of them are man-made.
The history of the dog, and its transformation from wolf to domestic companion, goes back deep in prehistory, to the settlements of early hunter-gatherer peoples. In these primitive communities, wolves would scavenge among the litter around the camp site and were a useful source of hides and meat.
The wolves might also, inadvertently, raise the alarm should an intruder or outsider approach the camp. Just why people first brought wolves into the domestic circle can perhaps be partly explained by the fact that humans in general seem programmed to adopt animals, either as playmates or status symbols.
Possibly a small furry wolf cub appealed to our ancestors as much as it would to anyone today. Being social animals, wolves that became campside hangers-on may have readily made the transition between bonding with their pack and bonding with humans, particularly if there were advantages in terms of food and shelter.
Whenever and wherever it happened, as wolves were domesticated, both their appearance and temperament began to change. New types of canid emerged, and their diversity was increased by crossbreeding between different dog populations.
Initially people began to develop distinct types of dog for particular jobs—hounds to hunt game, mastiffs to guard property, and shepherd dogs to herd livestock. They selectively bred these dogs to be physically and temperamentally suited for their role— keen noses for hunting, long legs for racing, strength and stamina for hard outdoor work, and a strong protective instinct in dogs needed for guard duties.
Later came the terriers and companion dogs. When humans better understood the laws of inheritance, and were able to manipulate them, the process of change was greatly accelerated. Then once dogs started to be kept more for companionship and as pets than for practical purposes, their appearance began to take precedence over function.
Dogs have come a long way in appearance and character since they were wolves, and while people continue to desire the company of canines, they are also likely to want to go on changing them. In some breeds, most obviously in dogs such as the husky types and the German Shepherd, wolf like characteristics still linger, in others the original template has been altered out of all recognition.