The Retriever, Dog, & Wildlife Blog

Something funny happens to the gene pools of domestic dogs. Breeders of pedigree Pekineses [sic] and Dalmatians go to elaborate lengths to stop the genes crossing from one gene pool to another. Stud books are kept, going back many generations, and miscegenation is the worst thing that can happen in the book of a pedigree breeder.  It is as though each breed of dog were incarcerated on its own little Ascension Island, kept apart from every other breed.  But the barrier to interbreeding is not blue water but human rules.  Geographically the breeds all overlap, but they might as well be on separate islands because of the way their owners police their mating opportunities.  Of course, from time to time the rules are broken. Like a rat stowing away on a ship to Ascension Island, a whippet bitch, say, escapes the leash and mates with a spaniel.  But the mongrel puppies that result, however loved they may be as individuals, are cast off the island labelled Pedigree Whippet.  Other pure-bred whippets ensure that the gene pool of the virtual island labelled Whippet continues uncontaminated.  There are hundreds of man-made ‘islands’, one for each breed of pedigree dog. Pedigree whippets or Pomeranians are to be found in many different places around the world, and cars, ships, and planes are used to ferry the genes from one geographical place to another. The virtual genetic island that is the Pekinese [sic] gene pool overlaps geographically, but not genetically (except when a bitch breaks over), with the virtual genetic island that is boxer gene pool and the virtual island that is the St. Bernard gene pool (pg. 33-34)

–Richard Dawkins The Greatest Show on Earth: The Evidence for Evolution (2010)

This passage from Richard Dawkins’s work is really the best explanation of the problems facing purebred dogs today.

No. Dawkins is not necessarily opposed to man creating these “islands.”  He does not make this criticism.

Instead, he uses it as way to show how geographic isolation can create new species. The lack gene flow between related population can create entirely genetically distinct populations that can become unique species over time.

With dogs, the “islands” are  utterly contrived. With the possible exception of giant breeds mating with the smallest toys, dogs are all capable of interbreeding. Dogs can also interbreed with wolves– their wild ancestor– golden jackals, coyotes, and Ethiopian wolves. There are behavioral barriers that normally keep dogs from swamping these other species with their genes.

But there are no behavioral barriers that stop dogs from very different breeds from mating with each other.

Humans have decided that the breeds will remain islands.

The problem is those islands didn’t have a very large founding population.

And what’s more, the mating systems within those islands are not random.

They aren’t really based upon Darwinian selection pressures either. They are bred solely upon human caprice and fashion.

Even working-bred dogs that are used for trials are based upon human selection.

And in most breeds, the real problem is that very few male dogs wind up siring too many puppies per generation. He may not be the healthiest dog in the population. His dominance has nothing to do with his fitness but rather how well he fits what humans perceive as the ideal in either trials or shows.

This is a recipe for genetic depauperation.

But the truth of the matter is that these islands are very new to dogs.

It has been only in the past century or so that a huge percentage of dogs in Western countries have been placed  in genetic islands.

Historically, dogs were bred for purpose. No one cared what they looked like. It was only that they were able to do the task at hand.

In many societies, dogs freely roamed, mating with bitches as they encountered them. The pups born from these populations would then be selected for whether they fit the task or not.

Breeds that existed were developed from very diverse populations, and selected for whether they fit that task.

This is very similar to the way natural selection works to create new species. Sexual reproduction produces variety,  and some of the variety produced has advantages in survival.  Ancestral swift foxes living in the arctic would occasionally produce kits that had lighter-colred winter fur. Lighter-colored winter fur is an advantage in places where the snow is on the ground for much of the year, and over time, these swift foxes became a specialized form that was well-adapted to living in the arctic. We call them arctic foxes.

In the same way, people would select for water dogs that were faster swimmers, and they discovered that dogs that had a bit more webbing between the toes were actually better swimmers. Over time, we developed dogs with very webbed feet and fast swimming abilities.  Thousands of years ago, people selected dogs that were fast sprinters, selecting heavily from dogs with the double-suspension rotary gallop. They created a canine cheetah, just from the variation that dogs were producing in their litters.

But in all of these populations, there was some variation.

It was only with the rise of the institution known as “the dog fancy” in the middle part of the nineteenth century that keeping dogs pure became virtue unto itself. It is certainly true that people kept inbred strains of dog before this time, and there are indeed accounts of people trying to avoid crossing different types of dog hundreds of years before this time.

But the fancy came about mainly because two things happened: technological advances meant that industrialized countries were now quite wealthy and democratization had meant that a large percentage of the population could now claim a bit of this wealth.  Democratization had led to policies favoring higher wages and more leisure time, and both of these assets meant that a larger percentage of the population could do the things that had previously been accessible to only the wealthy.

When dog shows became mass activities,  the caprices of fashion took over. Breeds did not remain static.  The fashions of the ring often led to dogs derived from different strains winning prizes at different shows and at different times.

So in many breeds, it was decided that the best way to keep the dogs of a constant type was to close off the registry. I cannot find the oldest example of a closed registry breed, but it surely dates to no later the end of the nineteenth century.

Once the registry is close, the variation is instantly truncated.  A breed club can then divine a breed standard and the breed the dogs to fit that standard.

Consistency of type is maintained over time, but the rigors of selection and the finite nature of the founding gene pool mean that the animals are put at an increased risk for genetic disease. All sexually reproducing organisms have some genetic tendencies toward disease. It is the fact that reproduce through sexual reproduction that keeps many of these diseases from being exposed. When a population becomes closed off in this fashion, the tendency for some of these diseases to come to the fore is greatly increased. It becomes even more so, when the breeding system becomes based upon breeding from elite sires.

In closed breeding population, the descendants do become more and more related over time, but if just a few elite sires are producing a huge percentage of the offspring in each generation, then this process becomes accelerated. When related individuals are bred together, the greater the likelihood of them producing offspring with genetic disease.  In an entirely outbred population, these genetic diseases become statistically less likely.

Typically these described as deleterious or harmful recessives, but they can have a very complex mode of inheritance– see hip dysplasia.

When these diseases started to come to the fore, it was decided that the first thing that should be done is to breed the diseases out.

In some cases they were successful.  Golden retrievers don’t suffer from hip dysplasia at the same rate they did twenty years ago.

But when you select for or against a feature in a closed population, you cannot avoid selected for or against something else.

Dog breeding is like economics– a very dismal science. The notion of an opportunity cost is always there.  If one breeds for something, one automatically selects against something else.  One cannot always see the consequences of selection in phenotype. For example, Western dog breeders have selected for heavy wrinkling in shar-peis, but the exact same gene that causes the heavy wrinkles also causes the periodic fever disease in this breed. When Portuguese water dog breeders funded a program that provided a genetic test for “improper coat”– feathered like a golden retriever, instead of poodle-type–they were warned that it was a bad idea for breeders to select against the recessive improper coat. Selecting against this coat might lead to a selection against an important variant of a regulatory gene in the breed, which would be very bad for a breed that has some issues with genetic diversity.

Domestic dogs have only been relegated to these islands for a comparatively short time, but it’s pretty clear that we aren’t able to control all the genetic diseases or potential genetic diseases within these island.

Dog breeders like to pretend that they are controlling these diseases. I remember reading a website that gloated over how much Scottish terrier breeders had reduced von Willebrand’s disease in the breed within a decade. However, over that same time period, the incidence of cancer in Scottish terriers greatly increased, and the average lifespan dropped to 10.15 years.

It is here the that concept of the opportunity cost appears once again. Von Willebrand’s disease’s inheritance is well-understood, and it is much easier to select away from it. Cancer is much more complex, and it’s much harder to breed out. Maybe they should have worked on reducing cancer rates in the breed through breeding from long-lived studs instead of carefully selecting away from von Willebrand’s.

But in the end, all we’re doing is playing the whack-a-mole game with genetic diseases. We are hitting one, and another pops up.

The only way to get out of this cycle is to change the breeding system.

We can increase genetic diversity within the islands.

We can make sure that elite sires don’t swamp the gene pool.  We can stop rewarding “outstanding sires” in breed clubs. We can place limits on how many litters a male can sire his lifetime.

We can also make sure that more than just a few puppies in each litter winds up producing offspring. In our current system, we want only a few pups per litter having offspring, but if more puppies are being allowed to breed, then more of their parents’ genes will be spread through the population.

But the best way is to do away with the islands altogether.

I’m not saying that we should scrap the concept of breed entirely. I think there is a reason why someone would chose a particular breed over another.

However, one thing we have learned is that the genetic differences between breeds are quite small.

Golden retrievers, for example, are mostly derived from St. John’s water dogs that have been selected for two recessive traits– the yellow to red color and the feathered coat. If one breeds a golden to a yellow Labrador that does not have the recessive long-haired allele, the pups will be smooth-coated. However, they will carry the long-haired allele, and when bred back to a golden retriever, the chances are very high that some of the puppies would have feathering and would be virtually indistinguishable from typical golden retrievers.

Indeed,  many golden retrievers descend from a yellow Labrador named Hayler’s Defender, who was crossed into the breed in 1929. His descendants don’t have much Labrador in them, but even his closer descendants looked just like normal golden retrievers. In those days, you could interbreed two retriever breeds, and after two generations of them being bred back into one of the constituent breeds, then the puppies could be registered as pure.

Furthermore, golden retrievers are derived from the same root stock as the flat-coated retriever, and detailed analysis of their genomes reveals that they are very closely related. Flat-coated retrievers are quite genetically depauperate and suffer from a very high incidence of cancer.  Consequently, their average lifespans are significantly shorter than those of golden retrievers, which also have a high incidence of cancer.

Golden retrievers also descend from at least one well-known curly-coated retriever. He was black and curly, but all of his golden retriever descendants look like golden retrievers.

For much of their history, retrievers didn’t exist as breeds. There were only two divisions:  a curly-coated retriever and a way-coated retriever/St. John’s water dog type, which included feathered and smooth coats. The dogs that became the Chesapeake Bay retriever in the United States were all interbred short-coated, curly-coated, and long-coated dogs.

Interbreeding was not seen as a disease.

But now it is entirely forbidden– though special dispensation is given to service dog organizations that cross golden and Labrador retrievers.

The modern dog fancy has contrived these islands.

These islands have provided a lot of consistency in type, but over time, they have produced a lot of misery.

Now, we have breeding populations coping with varying levels of genetic load.

It’s not getting significantly better in any of them. In most, it’s getting significantly worse.

So are we going to try to manage these islands, which will ultimately be a losing battle, or are we going to make the common sense changes that are needed?

I would like to think that the latter will happen.

But I know it won’t.

Or rather it will only happen once the kennel clubs are brought kicking and screaming to reform because the law has decided to intervene.

People love dogs.

I mean really love them.

In the past few decades, the status of the dog has greatly increased in the West.

People want dogs that live good lives. They want them to healthy and comfortable.

The vast majority of the dog owning public is appalled when they find out how cavalier breeders are about breeding for unhealthy conformation.  They will be appalled when the find out how many people in the dog fancy deny the concepts of population genetics and hold onto blood purity as a religious dogma.

People are starting to learn these things.

And the dog fancy had better understand it.

The old ways just won’t cut it anymore.

It must adapt. It must embrace science.

It must do away with that which it cannot defend rationally and logically.

It must listen to the real experts– i.e., real scientists and not someone who has “been in Clumber spaniels for 40 years.”

The islands we have contrived are not serving dogs well.

We need something better. We need to allow for greater diversity in genes and a greater diversity in phenotype.

Dogs deserve so much more.

We cannot solve problems by holding onto erroneous ideas of the past.

We can only solve them when we embrace new ideas that are well-grounded in science.

The hope for dogs is that science triumphs over dogma.

And maybe it will.

It may just be a matter of time.