At some point, people living in proximity to dogs got the idea that dogs might be useful for more than just eating trash. Dogs bark to warn each other when there's an intruder. Their superior senses of smell and hearing make them better at spotting prey than human hunters, and their size and agility make them better at flushing and catching it.
According to the Coppingers, wild wolves are predators and their behavior follows a seven-step sequence:
First, the wolf notices its prey. Then it focuses intently on the prey (sometimes called giving "the eye") and stalks in a slinking motion to prepare for the chase. The chase can culminate in either a grab/bite or kill/bite, and this sequence can break down before the kill or dissect stage.
Wolves must use all of these behaviors to survive. In dogs, this pattern breaks down. The pariah dogs don't need all these behaviors if they're primarily scavengers. As people have bred dogs, they have pulled the pattern apart, emphasizing certain aspects and downplaying or eliminating others, depending on their purpose.
People can promote certain characteristics by either breeding pairs of dogs that share the desired qualities or by allowing dogs to breed randomly but culling puppies from the litter that do not possess those characteristics. In either case, the genetic frequency for the desired quality goes up in each generation.
Herding dogs must eye and stalk, but never bite or kill. Hounds chase. Retrievers must grab the prey but should not dissect. Dogs that did their job well were allowed to reproduce, those that didn't were not. With intense selection, traits can be fixed in just a few generations. At some point, the new dog type may be called a "breed."
A Border Collie herding goats closely resembles a wolf stalking its prey. The head is down, the body low to the ground, eyes riveted on the prey. However, the Border collie uses this behavior to move the goats, not hunt them. The amazing thing is that dogs are actually better at their section of the pattern than the wolves they descended from, they just don't have the whole set.
For a type of dog to be recognized as a breed, there must be a record of breeding going back generations. These animals must be "true breeding" -- that is, they must produce relatively homogenous offspring. For each breed recognized by groups such as the American Kennel Club, there exists some type of breed standard. This standard is a full description of what the ideal specimen of this breed should look like and how it should act. The standard can cover everything from coat color, length and texture to stance, attitude and eye shape. Not every purebred dog of this breed will look or act in accordance with the standard, but reputable breeders work towards this goal.
We'll take a look at purebred dogs and "designer mixes" next.