I love dogs, I’ve always loved dogs. But there’s always the debate... purebred or
It’s a great year to be a dog lover! Apparently 7 new dog 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, PUUPPIES, but the science part of me wants to know, why are there so many different
dog 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 dog 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 a “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 lead 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 within
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 humans mess with dog’s shape and coloring, they are actually 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 a dog’s
face, changes their brains too. In dogs with short snouts, their brains have rotated 15
degrees backwards and the smell region in their brain is in a completely different place
from other breeds. And these kinds of brain changes are common in other dogs too.
Another study also published in PLOS One found that Chiari malformation in dogs actually
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 basically 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 there
are responsible breeders who 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. At some point, dogs evolved to become man’s
best friend? When did this take place?
So what’s your fav dog breed? Mine’s a mutt.