I have to be tough on the way the question has been asked in the title. Firstly, all cats do not look the same. There are some cats which have been bred to extreme which I mention below. Secondly, dogs do have a wider range of appearances but they are all brothers under the skin; they are all the same species and they are all descended from the grey wolf. Fundamentally, their personality is the same. The American Kennel Club recognises 195 breeds and there are 360 recognised dog breeds worldwide. On my estimate there are just over 100 cat breeds but many are dormant and the major cat association, the Cat Fanciers’ Association recognises just 45 breeds. This illustrates the difference between purebred dogs and cats.
I’ve seen a range of dates as to how long people have been breeding domestic dogs. It varies from about 8,000 years to about 20,000 years or even longer. Whatever, the domestic dog has been selectively bred for longer than the domestic cat, first domesticated about 9,500 years ago. It is the selective breeding of dogs in following the breed standards as set down by the dog associations which has gradually separated them into a wide variety of sizes and appearances. At the extremes they have been bred with an enormous difference in size and general appearance, particularly facial appearance.
The St Bernard may weigh 300 times more than the little miniature Yorkshire Terrier and the Great Dane stands 40 inches at the shoulder which may be 10 times the height of a Yorkshire Terrier but they are brothers in terms of their interior anatomy and fundamental personalities.
Even the tiniest dog, perhaps a toy dog, believe that they are mighty wolves and they act like it sometimes. They may bark at the postman or deliver a deep-throated growl to a person approaching the house. Their voice might sound thin and yapping but inside their heads they are proud and dignified wolves. Sometimes a small toy dog may meet a big one in the park. Big dogs are sometimes nonplussed by the behaviour of small dogs who give them the same treatment. This is because there are strong inhibitions about attacking puppies. The big dog can become slightly confused because they are looking at an adult dog which looks like a puppy.
Selective breeding has reduced the numbers of over-nervous and over-aggressive individuals but expanded the number of breeds. They are more juvenile and playful, more amenable and better companions. But in the interests of creating a product which is attractive to humans the range has been extended. Perhaps I can use the analogy of any commercial product range which needs to be sold in numbers.
You can buy a very large range in terms of size of vacuum cleaners and fridges. The manufacturers want to satisfy the demands of a wide range of customers. Dog breeders are in the business of winning dog shows and satisfying customers. Celebrities like toy dogs so that they can carry them around under their arm as an accessory. There is a trend towards small dogs because they are more suitable to modern urban and stressed life. They are similar in size to domestic cats and might even be smaller. Perhaps they are a dog version of a cat. Perhaps in the future dog breeders will have created a companion animal with the appearance of a miniature dog and the personality of an independent cat which might be the ideal for some customers.
Utility – working dogs
Some dogs have been bred for high speed chasing with their long legs and slender bodies. Or they might have been bred as utility dogs for going to earth after vermin. These dogs have shorter legs. Lap dogs are obviously much smaller. As I understand it, early selective breeding was about utility whereas modern selective breeding is about appearance.
The working dogs include guard-dogs and sheep dogs and other breeds with specific functions such as the sledge-pulling Huskies. These are utility dogs. A modern factor for a dog is to be of a manageable size and a cute pet. The Pekinese is an example. They have an ancient history is high-status favourites of the rich and powerful. They have been bred for many centuries in this specialised role.
The question in the title really is referring to purebred dogs. The mongrels, the random bred dogs, are much less variable in appearance. They more conventional looking. They have the appearance that we expect of a dog. There are dog lovers who very much favour their much-loved pet mongrels. They perhaps dislike the pampered pedigrees which they argue are bred with inherited defects and compromised immune systems. Selective breeding is essentially inbreeding and inbreeding can result in “inbreeding depression” which is essentially a reduced immune system and bringing to the fore recessive genetic defects such as lameness which would normally be hidden and which are hidden in mongrels.
The great range in appearance of purebred dogs comes at a price which is historically hidden. However, in recent years it has been heavily discussed. In Britain, the Kennel Club were forced to take steps to improve the health of their registered breeds by sharpening up the breed standards to try and reduce extreme appearances. I think that they have failed in this regard but their major dog show, Crufts, was removed from BBC programming on the pretext that the Kennel Club was promoting the breeding of unhealthy dogs. In Germany they call this “torture breeding” and it applies to domestic cats as well.
Purebred cats – extremes
Domestic cats are generally very similar in size but the smallest is a fraction of the size of the largest in the purebred family. Random bred cats are all similar in size. The very large Maine Coon which we occasionally see on the Internet is many times larger than the smallest purebred cat namely the Singapura. And the bred-to-extreme Maine Coon, looking like a lion, follows the pattern seen in extreme bred dogs. The best known example of extreme cat breeding is the flat-faced Persian. The objective was to create an interesting and distinguishing appearance which has been met but at a price to the cat’s health which has breathing problems, a high percentage of polycystic kidney disease and tear duct overflow.
The point that I am making is that in the cat world there are also differences in appearance but it is on a smaller scale than for the dogs because they have been selectively bred for a shorter time.