Small and Large Dogs- How Size Variations Can Help Us Learn More About Diseases We Share With Dogs

Dogs are descended from wolves but the domestic dogs of today are quite different from the dogs of long ago. The largest variation in size of any animals that live on land is found among the various breeds of dogs. Because dogs and humans have more than 200 diseases in common and humans share about 85% of our genetic makeup with canines in general, it is important to study the variation of size found in dogs. There were probably smaller wolves in ancient times but we have no way of knowing for sure. These smaller canines would have been more likely to have been treated as pets by ancient men. This was the beginning of man wanting to breed smaller dogs for different uses, such as hunting, herding and watching for intruders.

The reason that we have dogs of such varying size is that breeders started using selective breeding hundreds of years ago. The smallest dogs from each litter were mated together, resulting in smaller and smaller dogs. Purebred dogs became less pure and finally the bloodlines were diluted to the point that the purest animals of each breed became almost extinct. It is for this reason that we are able to learn so much from the diseases we share in common with dogs. These diseases include cancer, high blood pressure and arthritis.

Small dogs have a mutation in one of their chromosomes that accounts for the growth sequence from birth to adolescence in mammals. By studying this gene and the hormone it controls we can put the pieces of the puzzle together in a way that was previously unknown.

By learning more about the similarities between humans and dogs we can find out new ways to treat and prevent many diseases that we have in common. This is just one more way that dogs are truly man's best friend.