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Do you like cats or dogs? If you like cats, this question might be a difficult one. Although, to be fair, there are a lot of cats, aren't there? Maine Coons, Tonkinese cats, Russian Blues; but today we'll focus on dogs.
The American Kennel Club recognizes 200 different dog breeds. However, they also acknowledge that there are 340 different breeds worldwide. In case you're wondering, there are at least 73 recognized cat breeds, but the official designation and recognition of cats is somewhat less rigorous and thorough than for dogs.
Now try to imagine any other animal you can think of. How many breeds of giraffes do you think there are? What about chimpanzees? What about humans? There may have been more than 21 human species at one time, but that's not quite the same. Besides, compared to the 340 breeds, that's still a pretty tiny number.
A breed and a species are definitely not the same thing. A breed is a specific group within a species that has been bred or modified to achieve specific characteristics. This is why a Chihuahua can be crossed with a Maltese. A Doberman can be crossed with a German Shepherd. They all essentially belong to the same species. It's just that years of careful selective breeding have been aimed at identifying specific characteristics in each breed that make them distinctly different. This doesn't happen in the wild, where speciation can be part of the evolutionary process, and one species eventually diverges from another.
Even knowing this, the number of dog breeds is simply staggering. Only horses are more diverse: there are over 400 breeds, and some sources put the number at nearly 800, but horses have been used for far more tasks than dogs.
Domestication of dogs
All the tail-wagging dogs considered the best in the world today trace their origins to a single species of now-extinct wolf closely related to the modern gray wolf. Genetic testing confirms this.
As for when dogs were domesticated, that's a bit more difficult to answer. Some sources suggest it occurred around 15,000 years ago. But there's also evidence that it could have happened as early as 40,000 years ago. And there's evidence that wolves may have begun their journey toward becoming fully fledged dogs as early as 130,000 years ago. This means that while we were getting to know our four-legged friends, it's entirely possible that Neanderthals were doing the same.
While the official date of domestication remains in question, so does its location. In fact, there is some evidence that dogs may have been domesticated twice, in two completely different places: once in Asia and once in Europe. However, the scientific community is divided on this point. Other researchers have found evidence that Europe is the sole site of domestication.
Genetic evidence suggests that dogs arrived in North America at the same time as humans, over 10,000 years ago, via the Bering Strait. Many of these Asian-origin dogs were bred by Europeans after their arrival and colonization, but some have survived to this day. This genetic history is particularly evident in species such as the Peruvian Hairless Dog and the Xoloitzcuintle.
Breed differentiation
Dog breeding is a very ancient practice. As we've already mentioned, there are many horse breeds, so humanity has a history of breeding animals for specific purposes. We have workhorses, racehorses, show horses, and so on. Humanity long ago realized that it's possible to take two animals with desired characteristics, cross them, and produce offspring that will also possess the desired characteristics.
Dogs were likely originally bred for hunting, guarding, and herding before moving on to other uses. Over the centuries, these dogs were divided into more specific groups, resulting in today's sheepdogs, collies, Australian shepherds, and other breeds that are herding dogs but have distinct appearances.
Herding dogs have been bred for centuries in various locations. Although all herding dogs are designed for the same task, their genetics can be quite diverse. It may seem as if they all originated in the same place, but research shows this is not the case. And, in fact, not all dogs hunt the same way. Some were bred to be very independent and live with a flock they tend. Others are much more dependent on their human companions. The methods and strategies used by these dogs vary significantly, indicating that the breeds arose independently along different paths.
Although working and hunting dogs trace their lineage back quite far, most of them emerged only during the Victorian era. At that time, dog breeding was truly widespread, and not all dogs bred were intended for work. Darwin's theories were cutting-edge, and the Victorians were fascinated by the idea of natural selection. They wanted to try their hand at breeding dogs with the qualities they were looking for.
The influence of selection
The results of selective breeding are clearly evident in documentary sources. Numerous comparisons of images of dogs from a century ago with modern ones can be found online. The differences in appearance between breeds can be striking. Bull Terriers a century ago were practically unrecognizable compared to modern standards. Modern Pugs and Boston Terriers have much flatter noses, which can cause serious health problems. Modern Shetland Sheepdogs are almost twice the size they were a century ago.
All of these changes were deliberate choices by breeders, and now, in modern times, they are expected characteristics, regardless of whether they are beneficial or detrimental to the breed. While dogs were once bred for a specific purpose, for work, modern dogs are often bred solely for aesthetics, without due regard for the animals themselves. As a result, some dogs can develop health problems, ranging from bone disease, respiratory and vision issues, to behavioral issues such as aggression.
Another problem with selective breeding, especially for what people consider purebreds, is the lack of genetic diversity. This could mean that dogs that are too closely related genetically will continue to exacerbate health problems in the next generation unless the genetics are corrected. This is one of the many reasons why some people believe it's better to adopt dogs from shelters than to buy puppies from breeders, not to mention that breeding can often be a cruel and grueling process for the dogs involved, who are forced to reproduce constantly.
Why do different breeds still look the same?
The vast diversity of dog breeds poses a challenge when it comes to breeding. Since all dogs are genetically related to the same species, they can breed with each other. At first glance, this doesn't seem like a problem until you consider a Chihuahua and a Great Dane. Scientifically, there's no reason why these two dogs couldn't mate. But in practice, this can be disastrous, especially if the Chihuahua is female. A female Chihuahua might not even be able to bear the puppies of a Great Dane, so attempting to breed them would be highly unethical and cruel.
Even if all the arrangements had gone smoothly, the resulting puppies could have been very sick. The resulting puppies could have developed a variety of unexpected health problems. These could range from physical issues caused by the three differences to serious behavioral issues.
The reason this combination is still potentially successful at the genetic level is that there's no real difference at the genetic level. Breeding dogs is little different from genetically engineering apples. A farmer can cross-breed two sweet apple varieties to produce a single, super-sweet apple. The new fruit, of course, will still be an apple.
Is it possible that dog breeds will one day become separate species? As distinct as red and gray wolves? Never say never, but it's unlikely. It takes hundreds of thousands of years for mammals to evolve into distinct species, distinct from their closest relatives. Remember, Neanderthals and Homo sapiens—that's us—were both human. We could successfully interbreed with them, and, in fact, we did.
For a dog breed to become a new species, it would have to be isolated from all other dog breeds for tens of thousands of years and undergo a process of evolution, mutation, and adaptation until it became sufficiently distinct at the genetic level to be considered something new. Our targeted breeding has changed the dog's phenotype, its appearance, but the genotype—essentially, what it is inside—remains the same.
Why are there more dogs than cats?
So, if you're still around, you might be wondering why there are so many more varieties of dogs than cats. If only a few dogs were bred for working purposes, and many more were bred purely for aesthetics, why are there still so many of them, outnumbering cats?
Moreover, regardless of the numbers, why do dog breeds vary so greatly physically, while most cat breeds look virtually identical? Admittedly, the differences between cat breeds are quite subtle. If you looked at a Siamese cat, a Persian cat, a Sphynx, and a Maine Coon, you'd hardly think they were completely different animals. However, if someone were to first encounter dogs and saw a Great Dane, a Chihuahua, a Pug, and a Greyhound, they might wonder whether they were all the same animal.
Firstly, it's unlikely that cats have been human companions for as long as dogs. Apparently, cats were domesticated approximately 10,000–12,000 years ago. Dogs were bred for thousands of years to produce the hunting, herding, and guard dogs we've discussed. Cats, on the other hand, weren't bred for anything in particular, especially until the last century. And even then, we used them only for aesthetic purposes, not for work. As a result, dogs vary greatly in appearance, as they serve different purposes.
Cats—no offense intended—have no purpose. They might serve as barn hands or mousers, but they don't require any special skills or physical fitness for that. Generally speaking, dogs are more useful than cats, which is why we have more breeds.
The psychology of cats and dogs also differs. Cats are known to be very independent. People often joke that they don't listen to their owners at all. This is generally true. This means that breeding them for specific purposes isn't always ideal.
Dogs, on the other hand, descended from wolves. Wolves are pack animals and are accustomed to working in groups. Even in the wild, leashes were once used for hunting. They have a genetic predisposition to obey commands, making them ideal companions for humans. Early humans understood that dogs would respond to commands under certain circumstances, and their eagerness to please and intelligence made them a logical choice for work.
However, it's worth noting that there are rare cat breeds that defy stereotypes. For example, the Savannah was bred from servals and domestic cats. The result is an animal significantly larger than typical representatives of the breed. A healthy Savannah can weigh up to 13.6 kg. The average domestic cat typically weighs between 3.6 and 5.5 kg. Thus, some creative experiments occur in cat breeding, resulting in giants like Great Danes, but these are much less common, and besides the Savannah, few other breeds meet these criteria.
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