There are between 350 and 400 breeds of dogs, and, while we know that dogs have been co-living with humans for thousands of years, most of these breeds are relatively recent, less than 100-year-old.
Surprisingly, not a lot differentiates a 4 pounds Chihuahua from a 175 pounds Great Dane. Genetically, at least. And those differences all came from human intervention. It would have taken thousands of years of natural breeding to come up with some genetic differences…and it is unlikely that such extremes would have happened naturally. Natural selection happens when a change is beneficial to the evolution of species.
And here, it is not the case. The changes we see among dogs are not so much a response to environment changes or the species’ needs, as they are a response to humans needs. Humans at first bred dogs for specific tasks, for instance hunting or guarding, then out of personal taste and companionship needs (dog toys), and then perhaps even out of curiosity. Dachshunds, for instance, came from a mix between terriers and a basset hound: The resulting new breed is a short hunting dog with stubby legs that has the proper shape to get into animals’ lair. Strong and tall dogs were bred to hunt big prey such as wild boars, and also to be used as convincing, and dissuasive, guard dogs. Some other dogs were bred for their cute features and their tininess; the Pomeranians or the Caniche Toys are good examples. Natural selection plays no role in this evolution, or in the species’ future. Humans are responsible from their survival, and breeds continue to get bred if they are popular or useful to humans, regardless of their “survival features”.
According to the National Geographic, all these physical differences in size, shapes, fur types, ears position and shape, colors, etc. that together defines a breed’s appearance are controlled by only 50 genes combinations. And all these physical traits are often concentrated in only one gene: For instance, chromosome 10 or CFA10 will determine whether a dog has its ear erect or floppy.
Look at this interesting illustration that shows the result of three genes on a dog’s fur type (its texture, long vs short and its facial hair).
If a dog has none of these genes mixes, then it will have short and thin hair, like a Doberman’s.
Genetics do not only influence physical traits, but also general behaviour and temperament. For example, Tibetan Mastiffs are known to be very loyal and protective of their owners, while Huskies are somewhat independent toward their owners and social toward strangers. Genetics can also have an impact on behavioural problems. Some dog breeds are known to be more sensitive. Sometimes, some of these dogs end up being psychologically fragile and stressed – even if they are raised in a great environment, their genetics might lead to anxiety and reactivity problems.
Genetics is a science, and a complex one. Good breeders will work hard to breed dogs that have all the physical and psychological traits that well represent their breed. Obviously, they will also make sure that their puppies do not have any of the genetic flaws and diseases that might have came up into the breed due to poor breeding.
Studying canine genetics is not only important to have healthy, beautiful balanced dogs: Studying canine genetics also help us understanding better our own human genetics. Because dogs were bred by humans “quickly”, their genome is simpler, with some characteristics behind spread on a limited number of genes, making it easier to identify the source of a particular illness or condition. Once we have located the genetic issue on the canine genome, it is a lot simpler to understand it and to locate it on the more complex human genome. For instance, we have recently understood that the epilepsy problem found in the Dachshunds can be tracked down to a single gene, giving us a lot of information that will eventually benefit those suffering from this condition.
Dogs really are man’s best friend!
cc National Geographic