Most researchers agree that the ancestors of dogs were wolves. Humans started raising dogs about 100,000 years ago. The remains of dogs have been found in prehistoric human settlements across the globe.

DNA tests in recent years have found some 450 breeds of dog throughout the world. This diversity is in part due to their human owners who have long participated in crossbreeding dogs.

In the long years that dogs accompanied humans, they were given various tasks, such as guarding houses, guiding the disabled, protecting cattle, fighting, sending messages and even warming the bare feet of pilgrims in temple s.

These different roles have helped shape the canine diversity that exists today. According to the online library of Oracle's ThinkQuest (http://library.thinkquest.org/), the American Kennel Club recognizes 148 breeds and divides them into seven groups:

Terrier: Fox Terriers, Airedale Terriers and others that were originally used to hunt prey such as foxes, badgers and rabbits;

Working: Collies, German shepherds, St Bernards and others who are muscular, even-tempered and obedient and serve humans as guards, guides and herders;

Sporting: pointers, retrievers, setters and spaniels who hunt using scent in the air;

Hound: beagles, foxhounds and bloodhounds who track their prey using scent on the ground. There are also the greyhound types such as whippets, borzois and salukis that hunt mainly by sight;