I love dogs, I’ve always loved dogs. But there’s always the debate purebred or mutt? It’s a great year to be a dog lover! Apparently, seven new breeds will be shown at the Westminster dog show! I don’t know about you, but dog shows… give me mixed feels. On a personal level, PUPPIES, but the science part of me wants to know, why are there so many different breeds and is that good for the species? I mean domesticated dogs might have been around for 40,000 years, and all pretty much looked like wolves.
But the few hundred dog breeds we know and love today, have only been around for a couple of hundred years at the most. Humans tinkered with dogs, selecting for temperament or physical traits. Things like distinguishing markings, the color of a coat and other physical features like head and body shape. A new breed has to meet very specific requirements to qualify as an official breed. Many organizations like the American Kennel Club demand proof that every dog used to make the new breed was a certified purebred. And in many cases, breeders need to get their dogs DNA and genotype tested to show an “an acceptable DNA variation sample for the breed.”
Since 2003, researchers have been able to see exactly what that genetic pool looks like thanks to an effort led by Ewen Kirkness at The Institute for Genome Research which sequenced the dog genome. They also studied the genomes of different breeds. And not surprisingly they found that the variation of genes was greater between dogs of different breeds than they were the same breed. So, a black lab and a golden lab will have less variation than a black lab and a bulldog. But what’s interesting is that variation can be as much as 27.5 percent between dogs of different breeds, even though essentially, they are the same species. Now compare that to humans who only have a genetic variation of 5.4 percent. When people mess with dog’s shape and coloring, they are messing with their genes.
Like size is pretty much controlled by one gene on chromosome 15 called Insulin-like growth factor-1 (IGF1), which is known to influence body size in humans and mice. But it’s mutation can be found in a lot of unrelated smaller breeds, suggesting it’s ancient. Even though it’s a few thousand years old, it’s a change that still happened faster than it would happen naturally. So all the tinkering humans do to dog breeds, dramatically changes dog’s genes faster than nature would.
With all that genetic tinkering, some weird stuff happened. Not surprisingly, breeding for aesthetic purposes has some.. unintended consequences. Like pug encephalitis and hip problems in German shepherds. And one study in PLOS One found that changing it’s face changes their brains too. In dogs with short snouts, their brains have rotated 15 degrees backward, and the smell region in their brain is in an entirely different place from other breeds. And these kinds of brain changes are common with other dogs too.
Another study also published in PLOS One found that Chiari malformation in dogs changes their skull and brain formation. It’s a physical defect that occurs in a lot of small dogs that are bred to look more “doll-like.” It makes the forehead bigger but also changes the brain shape. It can cause chronic conditions like headaches, problems with walking or even paralysis. One of the lead authors of the study Clare Rusbridge described the condition “as trying to fit a big foot into a small shoe.” Which just sounds utterly painful. The physical defects caused by inbreeding is a huge problem, and it’s one of the reasons why some breeders are calling for stricter regulations and practices. Thankfully some responsible breeders are using genetic science to ensure they are breeding to maintain genetic diversity, resulting in new breeds that are both healthy and happy. While we’ve bred dogs to be stronger, smaller, or even more docile, they all come from a wolf-like ancestor thousands of years ago. So what’s your fav dog breed? Mine’s a mutt.