Introduction

Have you ever wondered why your poodle follows you around the house like a 
shadow? Or why your beagle can't resist going over to your neighbor's 
backyard and exploring? Or why it seems that your golden retriever could 
play fetch with a stick for hours on end? Your dog naturally seems to have 
certain personality traits. The reason is selective breeding. Selective 
breeding means breeding an animal for a certain purpose or trait.

Selective breeding happens like this: you have a litter of puppies 
and you need dogs to herd sheep. The first step would be to take that litter 
and put them around the sheep to see which dog pays the most attention to 
the sheep. The second step would be to breed that dog to another dog that 
paid attention to the sheep. 

Animals are also selectively bred for physical characteristics. For example, 
you might breed only the biggest dogs to the biggest dogs, or only longest-
haired dogs to longest-haired dogs. 

Wolves were valued for their aid in hunting, guarding, herding, and as 
companions so wolves were domesticated and became dogs through a 
process of selective breeding over 400,000 years ago. Dogs (Canis lupus 
familiaris) are a subspecies of wolves (Canis lupus). 

Dogs were bred for certain functions, such as hunting, retrieving or 
herding. Bernese mountain dogs, with their thick coats and strong limbs, 
were bred to guard herds and flocks in the mountains. Bloodhounds and basset 
hounds, with their natural talent for following a scent, were bred for scent-
tracking jobs. Greyhounds, with their slim bodies and long legs, were 
capable of great speed and thus were bred for racing. Rottweilers, with 
their strong bodies and naturally assertive personalities, were bred as 
guard dogs. Each breed has a specific job to do.

Dog History
The dog traces its ancestry back to a five-toed, weasellike animal called 
Miacis, which lived about 40 million years ago. This animal was the forebear 
of the cat, raccoon, bear, and hyena, as well as of the wolf, fox, jackal, 
and dog. Miacis, undoubtedly a tree climber, probably also lived in a den. 

Next in evolutionary line from Miacis was an animal called Cynodictis, which 
somewhat resembled the modern dog. Cynodictis lived about 20 million years 
ago. Its fifth toe, which would eventually become the dewclaw, showed signs 
of shortening. Cynodictis had 42 teeth and probably the anal glands that a 
dog still has. Cynodictis was also developing feet and toes suited for 
running. The modern civet resembles that ancient animal.

After a few more intermediate stages, there was the extremely doglike animal 
called Tomarctus, which lived about 10 million years ago. Tomarctus probably 
developed the strong social instincts of dogs and most of its close 
relatives, excluding the fox. The Canidae, the family that includes the true 
dog and its close relatives, stemmed directly from Tomarctus. Members of the 
genus Canis, which includes the dog, wolf, and jackal developed into their 
present form about a million years ago. 

There were six known sub-species of wolf that developed into dogs:
*Canis lupus metris-optimae gave rise to the herding dogs like the 
German Shepherd and all sheepdogs and collies. 

*Canis lupus intermedius gave rise to the hunting dogs like the 
Basset Hound, Dalmatian, Beagle, Poodle, and all spaniels, setters, 
retrievers, and pointers. 

*Canis lupus leineri gave rise to the hounds like the Greyhound, 
Dachshunds, and all scent and sight hounds, harriers, and terriers. 

*Canis lupus inostranzewi gave rise to the mastiff family of dogs, 
which includes the Saint Bernard, Bulldog, Boxer, Pug, Newfoundland, Great 
Dane, Rottweiler, Elkhound, and all other mountain dogs. 

*Canis familiaris palustris gave rise to the working or draft dogs 
like the Eskimo breeds of Spitz, Chow Chow, Pomeranian, Malamute, Samoyed, 
Husky, and all other draft dogs. 

*Canis lupus chanco gave rise to the Lhasa apso, Pekingese, and Shih-
Tzu.

Genetic research has identified 14 ancient dog breeds. They are Afghan 
Hound, Akita, Alaskan Malamute, Basenji, Chow Chow, Lhasa Apso, Pekingese, 
Saluki, Samoyed, Shar-Pei, Shiba Inu, Shih Tzu, Siberian Husky and Tibetan 
Terrier. Because many of the 14 breeds came from China and Japan, the theory 
is that the dog originated in Asia 15,000 years ago.

There are several hundred dog breeds in the world today. There are many dog 
breeds because dogs have changed due to selective breeding for hair color, 
size, ability, and personality. The American Kennel Club officially 
recognizes 150 breeds, but many new breeds exist.