Ashley Shih, of Russley Primary School, asks :-

How were different breeds of dogs created from the first animal, presumeably the wolf?

Alex Davies, a veterinarian at Massey University, responded.

Dogs appear to have developed from a weasel-like, meat-eating animal called Miacis, which lived about 50 million years ago. Miacis was the ancestor not only of dogs but also of cats, bears, raccoons, civets, weasels, and skunks. A descendant of Miacis called Tomarctus appeared about 15 million years ago. Tomarctus resembled a wolf and is the direct ancestor of all members of the dog family, including wolves, coyotes, jackals, foxes, and domestic dogs.

The oldest site where fossilized human and dog remains occur together dates from about 8000 B.C. This means that people and dogs have lived with each other for at least 10,000 years, making the dog the oldest known domesticated animal. We think that prehistoric human beings first valued dogs as watchdogs. Later, people realized that dogs could also be used for herding and hunting other animals. Over thousands of years, such breeds as collies were developed to herd sheep, goats, and cattle. Hounds, pointers, retrievers, setters, spaniels, and terriers were bred for various kinds of hunting.

The process of breeding only the individuals in a species that show desired characteristics is called artificial selection, and it eventually leads to large changes in a species. For example, the various breeds of dogs differ widely in size, appearance, and behaviour. Dogs are remarkable for these differences, but no more so than what humans have done with cabbage, broccoli, kohlrabi, cauliflower, and Brussels sprouts which belong to a single species, selectively bred to develop different characteristics. Breeds of animals that have been maintained by artificial selection often revert to the wild form as seen in feral pigs and cats in New Zealand which are from domesticated stock but now are very much like the wild animals from which they descended. On the other hand, it is generally accepted that genetic change cannot be reversed, so don't expect that your pet chihuahua can ever become a wolf again.