Why Dogs Have Many Different Shapes and Sizes, and Cats Simply Do Not

Dogs and cats have been companions to humans for millennia. Approximately twenty thousand years ago dogs first appeared in the fossil record alongside humans. Their presence helped us to keep our settlements safe from predators, and over time the bond grew. Dogs began taking on more and more specialized tasks for us. Dogs began hunting, catching mice, herding animals, finding lost people, and when the people allowed it, simply being a pet!

It would be another ten thousand years before cats began to appear alongside humans, Cats, however, did not serve as many different functions in our homes as dogs did. If a cat wasn’t in charge of pest control for a home, it was likely that they were simply a pet, and kept for the enjoyment of humans. Of course, cats are particularly good at pest control, and this has earned them a favourable position in the hearts of many.

Selective breeding is the concept whereby humans note a particular trait that is either desirable, or confers a benefit to the species, and then the lineage of that animal is protected. This happened heavily with dogs as humans took note which features helped them with which functions. A dog that would help to hunt deer and moose required larger jaws, and a larger form, than a dog that would be used to catch mice. All of the varieties of dogs that we enjoy today are the direct result of human intervention on what was originally a wolf.

There was, of course, a downside to the selective breeding that led us to have so many different dog breeds. Any negative characteristics that the dog had alongside the trait being selected for had a very high chance of also being passed down through the lineage. This results in what has been referred to as breed problems today. Some examples of breed problems are the snout problems experienced by a pug or the hip and bone problems experienced by a golden retriever. These problems can be managed as they arise, but it would be up to the breeder to determine if the amplification of the problems is worth the amplification of the trait they are seeking.

Cats have undergone selective breeding as well though certainly to a lesser extent. There are a variety of pests in the world, and humans have a variety of tastes. Though there are a variety of pests in the world which may require slight changes in body dimensions to hunt, it is reasonable to assume that many of the different traits we see in cats today are the result of aesthetic preference in the humans who bred them.

With today’s modern understanding of genetics and how traits flow from one generation to another, more intelligent and directed breeding programs are in use. It is possible to select for certain traits within a lineage and at the same time eradicate the traits that you do not wish to remain. The process, however, becomes longer, more involved, and, as expected, more expensive. The average dog breeder loves their dogs though, and they wouldn’t let any of that slow them down.

It’s reasonable to assume that if the considerable effort was put in to breed larger cats, then the effort would not be wasted. However, cats have been shown to not lend themselves as much to the cooperative tasks that dogs currently perform for us. As such, since dogs have served us so well doing so many different jobs, the dogs themselves became as specialized as their tasks, while cats remain largely similar, with of course a few exceptions.

Sources:
1. Why Dog Breeds Look So Very Different, But Cats Don’t, https://www.livescience.com/59875-less-variety-in- cats -than- dogs.html
2. Why Dog Breeds Have So Much More Variety than Cat Breeds, https://www.businessinsider.com/why-dog-breeds-look-different- cats -do-not-science-breeding-pedigree-animals-2018-1