The first member of the prehistoric dog family that would be recognizable as a canine came into being roughly 30 million years ago. Known as Cynodesmus, this large coyote-type creature was just one of nature's many attempts to create a biologically successful canine.
Five million years later, Cynodesmus became a fatality of the evolutionary process. Hundreds of other "experimental" canines followed, including wolf-like dogs in North America that were the size of grizzly bears. Appearing four and five million years ago, these gigantic creatures became extinct long before man even considered the possibility of a canine companion.
Roughly a million and a half years ago, another interesting canine prototype, Canis dirus (the dire wolf), appeared in what would someday become Southern California. Fossils of these seven-foot long wolf-like creatures have been found by the thousands in the La Brea Tar Pits, snared in the tar while attempting to dine on trapped animals. On the basis of their scarred fossilized bones, paleontologists believe that savage battles took place between dire wolves and the massive saber-toothed tigers that existed at the same time.
Despite all the canine-like animals that came before the modern dog, there is no clear link between the prehistoric dog and members of the modern day genus known as Canis. Members of this classification include the domestic dog (canis familiaris), the coyote, jackal, dingo and wolf (canis lupus).
Paleontologists believe that the early members of the Canis genus appeared about a million years ago in Asia, Europe and the Americas. At that point, they all resembled wolves. Members of Canis that lived in cold climates were larger and a paler color then their smaller, yellow colored, southern cousins.
Originally, the members of Canis and humans competed for food and would even eat each other. As humans started to band together and live in caves (about 30,000 years ago), both man and wolf began to see the benefit of establishing a truce. Humans appreciated the way the wolf-dogs would bark when unknown animals or humans approached, warning them of potential danger. The wolf-dogs, in turn, enjoyed dining on the leftovers from man's hunting expeditions.
Approximately 20,000 years ago, man began an attempt to tame the wolf-dogs that lived near their cave settlements. The process may have begun when a hunter found a wild pup and brought it home to fatten up before eating -- only to discover that this entertaining ball of fur was far more useful as a helper than a meal.
During the Neolithic revolution (6,000 years ago), human communities came out of their caves and established villages near water. Instead of depending solely on hunting for survival, man began to plant crops. Scientists believe that during this period, the wolf-dog finally became a respected and valuable member of the human family -- making it the first animal to be domesticated by man. The division between those animals that would remain wolves and those that would become dogs was finally established.
As human society developed, man became more and more convinced of the usefulness of Canis familiaris. Dogs were trained to herd goats and sheep, to assist in hunting, to act as guards and to be companions. Human societies around the world selectively bred dogs to meet the needs and whims of their masters -- whether it was to pull a cart or to entertain an emperor. Today, man-made modifications have resulted in over 500 dog breeds -- more variety than any other species in the animal kingdom, with each designed to fulfill their own special niche as man's best friend.