Miacis, is described as a weasel sized small carnivore that lived 40 million years back in the Eocene period. This animal is believed to be the oldest ancestor of present day dogs. They were forest dwellers, smaller in size with long tail and short limbs.
Cynidictus was the next to evolve and the evolution of Hesperocyan is thought to be next stage. There are two views on the development of Miocene period was followed by Tomarectus of Pliocene period and then the present day canids. But there is another view that Hesperocyan and then Leptocyan may be the ancestors of dogs or even Tomarectus.
The immediate wild ancestors of the dogs are more or less accepted as wolves (Canis lupus). But there are other views like the possibility of mixing of jackal and wolves, which lacks fossil evidence.
The production of fertile offspring from the mating of wolf and dogs supports wolfian ancestry for dogs. Moreover the dog breed Alsatian has lot of similarities with wolf.
Dogs belong to the class Mammalia, sub class Metatheria, Order Carnivora, Family Canidae, Genus Canis and species familaris.
There are many speculations on the events that lead to emergence of dogs from wolves. The social structure of the wolf is very much similar to that of man and hence may be one of the reasons for its domestication.
Wolves might have followed the hunters initially to find game. This must have followed by sharing of killing by the man with wolves and subsequent taming of the animal. Or else early man may have taken young pups from the wolf’s den and hand raised it. In process they depend on man for its food and hence subsequent domestication.
The similarity between dogs and wolves are many including developmental factors like less developed masseter and temporalis muscles, shorter muzzle, wider cranium, reduced tympanic bullae, convex mandible, smaller eyes and teeth.
The differences between the two are mainly in the reproductive cycles which are twice as that of wolves in dogs. The age at sexual maturity is around one year for dogs and two years for wolves. The reduced or even absent scent gland in dorsal aspect of base of tail and presence of first digit on the rear limbs are peculiarities of dogs.
Around 12,000 years old remnants of dog like creatures have been discovered in different sites like Palegawra cave in Iraq and Ein mailaha in Israel. The presence of dog mummies along side those of Pharaohs in Egyptian pyramids was also noticed.
A single origin in Northern Euracia or emergence in different location is still fierecely-debated topic. Latest DNA evidence suggests at least two separate domestication events.
In the whole history of dogs there are more than 2000 breeds. Most of them had perished during the long battle with time and nature. It is estimated that currently 400 dog breeds are in existence in this world. The grouping of breeds varies according to the rules laid down by the various agencies.
The Federation of Cynologique Internationale (FCI) has grouped the dogs into 10 classes, where as American Kennel Club (AKC) and Kennel club of Britain (KC) have grouped all breeds into six classes.
AKC has a seventh class of miscellaneous breeds. The history of dogs suggests that the first competitive dog show was held at Newcastle in Britain in 1859. It was limited to pointers and setters. Later the kennel club of Britain was established in 1873.