The History of Dog Breeds

Tiny Chihuahua to burly Mastiff, all dogs are one species. Dogs are the most variable animal on the planet, showing so many differences among breeds it’s sometimes hard to imagine they are all one species.

Because all dogs are the same biological species, whether purebred or mixed, a breed is a race—a population containing genetically similar animals that differ in certain ways from other races. With dog breeds this is generally an artificial situation, effected by humans’ selective breeding.

Through the millennia since their domestication, dogs have been bred in a wide variety of types. Many of today’s breeds were established centuries ago, while some were already distinct thousands of years ago. Breeds range in size from tiny teacup purse dogs to mammoth burly animals a child can ride like a horse.

Different breeds have short hair, long hair, straight hair, curly hair, or even no hair at all over much of their body. There are dogs with extremely short legs and those with extremely long legs; those with long muzzles and those with squashed-in muzzles; those with powerful, rugged bodies and those with sleek, streamlined bodies.

Some breeds come in various colors and patterns, while the dogs of other breeds are all one color or pattern. Behavior also varies from breed to breed, with some dogs excelling at guarding, herding, hunting, retrieving, fighting, carrying loads, or other useful-to-people traits.

Dogs of certain breeds are more likely to attach themselves to one particular person, while others are happy for any human companionship, and a few are strictly working dogs with little suitability as house pets.
But a dog breed is more than just a bunch of dogs that look and behave alike. The individuals are genetically similar so that their offspring will also look and behave like the typical specimen of that breed.

New breeds are developed when a group of dogs is bred for certain traits, and then the traits are fixed through careful matings until the puppies all fit the standard for the new breed. The breeders then organize, start a studbook, and begin registering dogs in that breed. Registry organizations in various countries divide dog breeds into different groupings. Registries also differ in the breeds that they recognize.