Posts Tagged ‘inbreeding’



Humans have an aversion to inbreeding. We find the idea of two humans from the same family marrying and having children quite disgusting.

We also know that wild dogs have strong inbreeding avoidance behavior. Wolves and African wild dogs generally avoid mating with blood relatives. Most domestic dogs will mate with their relatives without reservation, and inbreeding has been a tool that dog breeders have used for centuries to establish type and promote homogeneity in their strains.

I have been a critic of inbreeding domestic dogs, but I now realize that I was cherry-picking the science a bit and playing up to human aversion to inbreeding to give a fully nuance and accurate understanding of what inbreeding can do to domestic dogs.

Inbreeding does tend to reduce MHC haplotype diversity over time, which can make dogs more susceptible to various maladies.  It also can increase the chance of deleterious recessive alleles from being inherited homozygously.  All of these are potential risks from inbreeding.

However, I would be remiss to say that inbreeding has not always been a horrible.  Indeed, certain breeds have been founded through a rigorous inbreeding and selection process that surely cannot be thought of as entirely disastrous to the strain.

A few years ago, I came across a book called Working Sheep Dogs: A Practical Guide to Breeding, Training and Handling by Tully Williams. In the text, Williams refers to Kyle Onstott’s work on dog breeding in which Onstott mention an experiment at the Wistar Institute involving rats. A “Miss King,” writes Onstott, bred rat siblings for twenty generations with a strong selection for vigor and stamina, and after twenty generations, she produced a strain of rats that were longer-lived, larger, and generally healthier than the average laboratory rat.

Onstott was a dog breeder and novelist, and his book on dog breeding was considered revolutionary when it was published in 1962. It is called The New Art of Breeding Better Dogsand I have been trying to get my hands on a copy.  However, I was able to glean from the names mentioned in Williams’s quote of Onstott that the “Miss King” of the Wistar Institute is Helen Dean King.  Dr. (not “Miss”) King was one of the early researcher on the question of inbreeding, and one of leading lights of the Wistar Institute’s rat breeding experiments.

I was able to find her study in which she was able to create the super rats strain through inbreeding, and yes, she was able to do so through rigorous selection for vigor.

In dogs, it is difficult to find a similar experiment, but then I realized one was quite literally staring me in the face.

Most are unaware that German shepherd dogs are all quite closely related to each other. Yes, they appear to have a lot genetic diversity, because we have all these quite different working and show-bred forms, but they all derive from a very similar inbreeding experiment to the one that Dr. King performed at the Wistar Institute.

Max von Stephanitz based the breed upon a Thuringian sheepdog named Horand von Grafrath, which he then bred to Bavarian and Swabian/Württemberg sheepdogs. He then tightly bred upon the progeny. Indeed, the entire breed is based off of three grandsons of Horand. They were Beowulf, Pilot, and Heinz von Starkenburg. They were bred mostly to other descendants of Horand, and there was strong selection for temperament and vitality in the population. It is in these foundations of the breed that wolf may have been added, but the breed still derives from these three grandsons of a single dog.

We can have lots of debates about this in the comments, but the German shepherd dog as an entire breed is fairly healthy for a large breed dog.  In that inbred population, the deleterious allele that leads to a degenerative myelopathy was part of the founders, and the breed itself does have that issue.  Some eye issues were also part of the founding population.

However, if inbreeding were always such a terrible thing, every dog in the breed would be a genetic basket case. Regardless of what one might think about show dogs, the working police and military dogs derive from this exact same inbred population, and it would be folly to say these dogs lacked vigor or were universally unhealthy and unsound creatures. Indeed, it can be argued that the most useful dog ever bred was the German shepherd dog. It has that much utility in a variety of situations.

Now,  I am not saying that inbreeding problems don’t exist. I am saying that we need a nuanced understanding of what inbreeding can do to dog populations, and it is not universally a horrible thing.

Inbreeding and rigorous selection can be a good thing for a strain.  Of course, I know there are breeds that do need some genetic rescue. The Doberman pinscher was founded in much the same way as the German shepherd, using a much more diverse group of domestic dogs in the foundation strain. However, the breed suffers so much from inherited DCM that it an outcross program could very well be justified.

But those of us who advocate rationalism and science in understanding and caring for dogs must keep an open mind. We must look at all the objective science and avoid appeals to human prejudice.

That’s what I’ve tried to do here. I am correcting some of my earlier errors, and I hope this helps lead to a more nuanced view of the subject.

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This scene should be part of a population management program for golden retrievers. Source for image.

This scene should be part of a population management program for golden retrievers. Source for image.

Let’s clear the air a bit.

When a dog breed is put into a closed registry system, it has been decided to create a population of animals that has a population genetics structure that resembles that of an endangered species. There is plenty of evidence that many very popular breeds have terrible genetic structures. In a 2008 paper in the journal Genetics, Calboli et al. performed an analysis of ten dog breeds in the UK, using Kennel Club pedigrees to determine effective population size. Effective population size tells you how big the population would be if a random number of individuals were put together that would have the same amount of genetic diversity as the population in question. The general rule for conservation genetics is that anything under 100 individuals is of critical concern.

The results went as follows:

Akita – 45 (effective population).
Boxer – 45
Bulldog – 48
Chow Chow – 50
Rough Collie – 33
Golden Retriever – 67
Greyhound – 17
German Shepherd – 76
Labrador – 114
English Springer Spaniel – 72

Shocking, eh?

Every one of these breeds is a closed registry breed.

All but one have very real problems with genetic diversity. Only the Labrador retriever is out of the crisis zone– and just barely.

If you read the paper, the golden retriever, which doesn’t look as bad, has the worst problems with popular sire effects in its population. Only 5% of the male dogs in the UK population are sires, and for a popular breed, this is a recipe for disaster.

This is because even though these dog breeds have a genetic structure resembling that of an endangered species, they are not bred the way conservationists would breed endangered species.

With endangered species, the goal is to conserve as much genetic diversity as possible.  The Chinese spend countless hours working to maintain what genetic diversity can be spared in giant pandas. Giant pandas, which are actually a primitive bear with no living close relatives left, have no populations for which there can be outcrosses.

You can’t say that about golden retrievers, which would be greatly served with occasional outcrosses to their somewhat more genetically diverse smooth-coated cousins. The differences between Labrador and golden retrievers aren’t that extreme. Both are derived from the same root stock. Both breeds share ancestors in documented pedigrees, and there was a famous cross between a yellow Labrador (Haylers Defender) to the Haulstone line of golden retrievers in the 1920’s.

Not ancient history at all!

If we had a dog culture that was based upon reason and science, this would be a no-brainer.

However, this is not the dog culture we have.

The dog culture we have does two things that utterly gum up the works when it comes to sound population management principles:

1. Closed registries as dogma.

2. Competitive dog breeding.

The former is what creates the genetically compromised population. The latter is what exacerbates it.

Could you imagine the madness that it would be to breed giant pandas based upon a conformation standard?

But that’s exactly what is happening in the world of dogs, and as I’ve noted before, it’s not just dog shows that are causing this problem.  Breeding choices that are based solely on trial performance do the exact same job.

Each generation of dogs that is bred under these conditions loses genes. Some of these genes might be pretty nice to have– like the gene that Dalmatians had for producing urine with normal levels of uric acid. This was actually lost to the entire population of Dalmatians before a pointer was crossed in to reintroduce it.

And it took decades and decades of fighting the closed registry dogma to get these Dalmatians into the breed. Even though they were very, very distantly derived from that pointer that was crossed in, the breed vanguards would not allow in the “mongrels.”

Until it became impossible to say no.

Every single breed in a closed registry system that is being bred with under these principles is at risk for winding up like the Dalmatian. What’s even more frightening is that as these breeds become more and more related through both popular sire problems and “line-breeding,” it becomes impossible to control for genetic load. Dog breeders operate under the delusion that you can just select away from any disease just like you’d select away from poor conformation, which is why they go ape over every genetic test for a disease that comes down the pike.

It’s not that these genetic tests aren’t useful. It’s that they do give dog breeders a crutch to hold onto. You can’t talk about  a better way to manage genetic load– i.e., let in new blood and selectively breed for better gene conservation– because everyone is awaiting the next genetic test to come along.

The problem is that the greater dog fancy is a culture that worships genetic plunder. Most of the effects of such pillage are not known while the pillaging is happening. During that time, a breeder might become rewarded with top winning dogs that may or may not have long lives.

But it is the next generations that the problems with gene loss and reduced genetic diversity start to become apparent. By then the breeder or breeders who plundered the genes may not even be around anymore.

But they have stolen from the next generation of dog owners and breeders.

It’s that next generation who will have to pay the vet bills and watch their dogs die agonizing deaths.

And all because we have contrived up endangered species that we call dog breeds and then bred them in ways that make absolutely no sense.

No one wants to talk about this genetic plunder.

And no one wants to talk about the simple fact that this concept of closed registry breed is really a very new concept. A breed is not a species. And although there are breed differences, when we start talking about breeds that are closely related, the differences become somewhat trivial.

And it is at this point the dog world becomes a dogma– a type of religion.

Breed becomes a faith-based assertion, and the dogs suffer because reason is not the operating force behind the management of their populations.

Dogma is.

Dogma is not good for dogs.




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The uploader of this video writes:

“say in not my dog, she’s my friend’s dog, and he want his dog to mate with her brother. don’t worry with the pups, they will come out cute again like my grey pup. i’m curious if what color will come out. sorry guys…. but inbreeding is ok to animals right? [NO!] it depends to the breeders if they want…”

If you inbreed, you’re playing with fire.

If you are breeding merle to merle, which is what dapple or “tiger” dachshunds are, this is what you can produce.

If you want dogs to have a high risk of producing dogs that are blind or deaf or both and have a heighten chance of being homozyogous for some deleterious recessive, then go ahead and breed them!

The stupidity of people never ceases to amaze me.


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Image from Cappella dei magi in Florence. Work by Benozzo Gozzoli.

A common misconception that continually gets spread is that domestic dogs were created through inbreeding wolves and that the different specialized breeds and types were created through inbreeding.

There is almost no evidence for either assertion.

The first assertion is easily falsified. Domestic dogs retained most of the wolf’s genetic diversity through domestication– in the neighborhood of 95 percent.  Wolves are a very genetically diverse species, so dogs, as a population, really do have a lot of genetic diversity for a domestic animal.

Further, there is no evidence that these specialized dogs were created through inbreeding.

Retrievers, for example, were always celebrated as being crossbred dogs. That’s right. For most of their history, different dog breeds were bred together to create retrievers of various types. It’s just the retrievers that derived mostly from the St. John’s water dogs that became the most celebrated and “improved” into modern breeds. Prior to modern breed formation, retrievers were bred through crosses in this fashion. Many retrievers had collie, St. John’s and Large Newfoundland, setter, and land and water spaniel ancestry, and others even had terrier and greyhound in them.

All they selected for was for dogs that would carry things in their mouths. And you can get that from a wide variety of dogs.

Now, retrievers are modern working dogs. Their exact function really didn’t become widely necessary until shotguns were invented. Before that, dogs like poodles and barbets were used for this purpose– and they were were often employed to retrieve shot arrows that missed their marks.

Earlier dog types were created, but they were created as landraces.  One of the oldest landraces is the tazi family of sighthounds. These dogs were among the earliest specialized dogs to have formed from the wolf. They are a very diverse lot. Some are shaggy. Some are smooth. Some are merely feathered.  But they are pretty genetically diverse as a landrace, and they are found from North Africa across the Middle East to China. In Asia, they are found from Siberia to India.

Because these dogs are pretty diverse, we know that they likely weren’t created by inbreeding. In fact, some regional variants have mtDNA squences that they share with local pariah dogs. The azawakh has mtDNA sequences that are similar to African village dogs, while Israeli salukis sometimes have mtDNA sequences in common with the Canaan dog.

So as this type evolved from the wolf, it likely incorporated genes from less specialized dogs. That’s not a closed registry system at all.

However, these dogs were selectively bred from genetically diverse stock over a long period of time.

This is very similar to the domestication process that Mark Derr describes in How the Dog Became the Dog Over tens of thousands of years, wolves and people began to affiliate with each other. This happened over a broad swathe of Eurasia. Over time, these wolves began to evolve into dogs.  During the last glacial maximum, Derr contends that the first phenotypically distinct domestic dogs appeared, largely because they were suffering from lack of prey for both humans and their socialized wolves to hunt. These dog features were not created through intense inbreeding, though the eventual development of the small dogs at the end of the Pleistocene may have been maintained by inbreeding.

At their founding, dogs were, by and large, genetically diverse.

This diversity was maintained in two ways.

Prior to the development of pastoralism, wolves were largely tolerated near human camps. Wild wolves and dogs exchanged genes quite a bit.

And humans were movers. In the days of the hunter-gatherers, dogs would always be on the move. If dogs are moving all the time, so are their genes. So there would always been a gene flow across Eurasia– and this would prevent any one population of dogs from becoming inbred.

Now, this is the exact opposite of what some people think. They think all of these dog breeds developed in complete isolation, and they regularly inbred to keep things going.

Actually, that wasn’t true even after the rise of agriculture around 10,000 years ago.

Once agriculture got started, people could remain in one place all the time, so it could be possible that people would start to become isolated– and their dogs would become inbred.

However, there were two aspects that always prevented this from happening.

One of these is trade. Trade has been a big thing even before humans began living in agricultural settlements. The earliest evidence of long-distance trade dates to as early as 150,000 years ago, and when settlement allowed people to produce more advanced goods, they were very interested in spreading it as far as possible.

Dogs had to have gone along with these early trading forays, leading to a continued gene flow.

Further, although most agriculturalists were sedentary, pastoralists never were.

Pastoralists were always following herds and flocks up and down mountains to access the best grazing, and in other areas, they moved their stock to better watering places from areas experiencing drought or dry seasons.

Everyone knows that dogs were and still are a vital asset to any pastoralist. They can alert the pastoralist to predators, and if the dogs are big enough, they can even kill them. They also can run off rustlers and bandits, and they can be used to manage the flocks and track down strays.

But because pastoralists are always moving, so are their dogs. And as their dogs move, they spread their genes.

One of the very good parts of Raymond Coppinger’s book is that he recognizes how important this movement of humans across these routes every year is very important to the story of the domestic dog. This movement is called “Transhumance,” and it has likely had a major role in maintaining genetic diversity in domestic dogs than we might have realized. Dogs traveling with pastoralists from village to village were mating with dogs belonging to villagers, and in this way, local genetic diversity was maintained.

The thing that actually created all the inbreeding in domestic dogs is the development of modern breeds.

Modern breeds that exist within a defined closed registry system are very new. They have only appeared in the past two hundred years– most in the last 150.

In this system, there was a delusion that one could continually improve upon the types and landraces by separating them from other dog stocks and then tightly breeding upon these dogs to set type. This exact same method was tried on cattle, sheep, and horses– and then fancy show pigeons. Results were quite substantial in those species, which were now much more productive, and the pigeons became more and more esoterically bizarre– the exact result the early pigeon fancy wanted!

In the early days, there were successes.

But over time, this sort of very close breeding and breeding within closed registry systems have had a deleterious effect upon domestic dogs.  Dogs within these breeds have lost 30 percent of their genetic diversity over the past two centuries.

Genetic diseases are encountered much more commonly in dog breeds than in almost all other organisms, though the notorious inbred factory farm turkeys are definitely more diseased in this fashion.

Many dog breeders exist under the delusion that they can breed out all the diseases their breed possesses. Many of these diseases are simple recessives, so all you’d have to do is inbreed to expose the disease and then cull. That works to a point.

But usually what happens is they select out a disease is they often wind up doubling down on something else.

Not all diseases are simple recessives either.  In fact, it has yet to be proven to me that the majority of them are.  Many are the result of several genes which are inherited in different ways, and it is very hard to selectively breed them out of a population.

The other problem is that the MHC haplotypes within any inbred population are very easily lost or become very homozygous rapidly. You cannot see MHC haplotypes, but if you breed them out and the dogs have more and more homozygous haplotypes, you will have a compromised immune system on your hands.

So you might breed out the easily defined genetic diseases, and in the end, you’ll wind up with dogs that are infertile or dying of autoimmune diseases– neither of which is uncommon in many dog breeds.

For tens of thousands of years, people have bred from genetically diverse dogs.

Now we’re seeing the full consequences of squandering genetic diversity in the name of delusion.

Diversity is the solution to so many problems in domestic dogs.

Unfortunately, the very notion of diversity conflicts with the long held shibboleths and bromides that underpin the dog fancy that has developed in the past two centuries.

Delusion is dangerous because it is more than a lie. It is a lie that the liar himself doesn’t know is untrue.

And to fight off the pesky truth, the deluded grabs at straws to excuse his delusions and make them true.

This, folks, is about 80 percent of what is written about dogs in the modern era.

Excusing and dismissing facts to hold onto delusion.

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San Nicolas island foxes (Urocyon littoralis) are thought to be least genetically diverse of all vertebrates. However, they have been able to maintain diversity and heterozygosity of their MHC haplotypes.

On my previous post entitled “Why is inbreeding bad?” I noted that one of the real issues with inbreeding is an impaired immune system as the result of losing diversity and heterozygosity in MHC/DLA haplotypes.

The MHC stands for the Major Histocompatibility Complex.  The MHC is cell surface molecule that is encoded by a relatively large gene family.  The MHC  molecule controls some of the actions of the leukocytes, “the white blood cells.”  As you might remember from your high school health class, leukocytes are the blood cells that act as police, taking out infectious diseases and foreign materials, including cancerous cells.

Possessing a greater diversity in MHC haplotypes allows the organism a heightened ability to control what leukocytes do when exposed to a variety of challenges to the immune system. Reduced diversity winds up restricting the immune system’s ability to fight disease.  Possessing a heterozygous MHC haplotypes also provides greater immune resistance than possessing homozygous MHC haplotypes.

In humans, the MHC is called the human leukocyte antigen system, usually abbreviated as HLA. In dogs, it is called the dog leukocyte antigen system, which is abbreviated at DLA.

One cannot look at an organism and tell what its MHC haplotypes are. It’s not like looking at fur or hair color.

And as a result, these haplotypes are very easily lost within a closed registry system.  Often, the haplotypes not lost entirely within a breed or strain, but because of the popular sire effect and continuous linebreeding  from “the best,” a huge percentage of the population in any one breed can be quite homozyous in its MHC haplotypes.

This has real health and welfare effects.  Autoimmune diseases are becoming more and more common in purebred dogs. Some breeds are highly susceptible to cancer, which might be partially the result of the decrease in MHC diversity of dogs within the closed registry system.  Allergies are also likely implicated to this reduction in MHC diversity and heterozygosity. The MHC also has some effect upon reproductive cells, which is one reason why certain breeds and strains have issues with fertility.

So what can be done?

Well, the easy answer is to do away with rigid closed registry systems and allow the different dog breeds to exist as very genetically diverse populations.

However, it is possible to breed for great MHC diversity in domestic dogs, even within the closed registry system.

To understand how this is possible, we will have to change species again.

Take the San Nicolas population of the island fox (Urocyon littoralis). This population is considered the least genetically variable of all sexually reproducing animals.

However, despite its lack of genetic diversity, this population of island fox has relatively diverse MHC haplotypes.

How does it do this?

Well, a study led by Andres Aguilar (2004)  found that the San Nicolas foxes likely were able to maintain their diverse MHC haplotypes through what is known as balancing selection. Balancing selection occurs when population keep multiple alleles actively maintained at frequencies that are higher than the mutation rate. It almost always happens within populations in better for an organism to be heterzygous for certain alleles than homozygous for them.

As we have seen with MHC haplotypes, it is better to be a heterzygote, so there is a strong selection pressure for the foxes to keep their MHC haplotypes diverse.

One way in which they likely do this is that they choose mates that have MHC haplotypes that are different from their own.

This might sound a little crazy, but even humans have innate mechanisms that are designed to keep our MHC haplotypes diverse.

There is a famous study in Switzerland that asked women which men were most attractive by smelling the shirts the men had slept in for two nights. Almost without exception, the women selected the men who had different MHC haplotypes from their own. The pheromones that are connected with sexual attraction in humans are also giving out genetic information such as what MHC haplotypes a potential mate might have.  And it’s so innate that women are able to obtain this information without understanding exactly what they are responding to.

It’s likely the same way in island foxes, which, like humans, typically reproduce within a bonded pair system. Foxes, like all wild dogs, are pretty particular about their mates. After all, the survival of their offspring is dependent upon having a partner that can provide for them.

Domestic dogs, for whatever reason, don’t seem to be as particular about their mates, and thus, it has been easier to selectively breed them.  Wolves and other wild dogs very rarely inbreed, but it is relatively easy to get dogs to inbreed and to do so for multiple generations.

And as a result, it has been easier for different breeds to lose their MHC haplotypes.

Further, it is not just the mere number of haplotypes a breed possesses. Heterozygosity has proven to be more important in determining immune health than just possessing a certain number of haplotypes.

That means that within an inbred population, there has to be some conscious effort to maintain both diversity and heterozygosity.

That is pretty hard to do when one is breeding for physical or behavioral traits– and the immune system genes cannot be readily ascertained.

Well, we do have a solution. Genoscoper currently offers an MHC II test, which would allow breeders to see what haplotypes their dogs posess and what to do with them. Mars Veterinary also offers a test that examines the MHC (among other things). It is called Optimal Selection from Wisdom Panel, and it was initially tested with breeders affiliated with the Dandie Dinmont Terrier Club of America (A NEW GENETIC BREEDING TOOL ON THE HORIZON (1)). Over a two year period, this selection tool has allowed Dandie Dinmont breeders to increase their litter sized from 2.75 to 4.0 puppies per litter. Dandie Dinmonts are a rare terrier breed that has issues with genetic diversity, and these tests could be a boon for breeds that have very small founding and effective populations.

So science now allows for us to do with domestic dogs what the San Nicolas island foxes were able to do on their own.  We can maintain relatively inbred populations and still keep the MHC haplotypes diverse and heterozygous.

However, here are some caveats:

First of all, virtually no dogs are bred without some eye to competition. Competition, whether in show or working trials, has a selection pressure of its own, and a breeder has to considered a wide variety of issues before choosing which dog to breed with which other dog. As I’ve noted before, MHC haplotypes are hard to see, so how many breeders would choose diversity and hetrozygosity of MHC haplotypes over the ability of the dog to win in the show ring or in the trial?  I would like to think that very few breeders would choose immune health over ribbons and titles, but that’s probably not the case.  Keeping the MHC diverse and heterozygous is a long-term project, and it requires a bit more dedication and discipline to breed for than physical or behavioral traits.

Further, breeders have to balance a wide variety of issues when selecting which dogs to breed, and MHC haplotype diversity alone should not be the sole criteria.  Other issues with temperament and hereditary diseases have to be considered in light of the MHC.

Finally, many of these breeds have either entirely lost MHC haplotypes or certain haplotypes are very rare within the breed.

You cannot do DIY balancing selection when you don’t have the haplotypes in the first place.

Even if we might have these tools, one should keep in mind that it is much more cost effective and easier to try to maintain genetic diversity within breeds and strains in the first place. It makes much more sense to keep breed registries more open and then operate selective breeding principles within much more diverse populations.  Breeding within much more diverse populations requires some understanding of how different traits are inherited, but one can readily learn these skills. It is not rocket science, but one can figure it out. If people living thousands of years ago0–before there was even a Mendelian theory of inheritance– were able to produce so many different types of dogs, then we surely can.

DIY balancing selection can be a tool within conservation genetics, but I think it has to be paired with a fundamental understanding of how population genetics works.

Otherwise, you’re going to get into silly arguments with people who think that you can just inbreed and inbreed without consequence. No rare dog breed can be saved in the long term if its immune system doesn’t work properly.

It’s really that simple.

In the end, selecting for diverse and heterozygous MHC haplotypes within a limited gene pool is less preferable than trying to maintain genetically diverse strain.  We have intentionally reduced genetic diversity within dog breeds and strains, yet as a population, dogs remain one of the most genetically diverse of all domestic animals. We have the ability to correct some of the errors without resorting to sophisticated genomic technology, but because the dog culture at large values purity and homozygosity at all costs, we are left looking at the only other option available.

Inbreeding requires so much scientific knowledge and acumen to pull off correctly that it really shouldn’t be done. And the validity registry systems that ultimately reduce dog breeds to inbred populations needs to be questioned.

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Inbreeding is bad for dogs.

Do I need to say this again?

It’s bad for dogs.

The only people who think it is good don’t know what they are talking about– or they have been so severely indoctrinated into the dog culture that they can’t see it.

Yes. Indoctrinated.

In virtually all of these dog registry and competition systems, there is a strong desire to produce a high level of homozygosity in either behavior or conformation. You win more consistently if you have more homozygosity in your lines. It doesn’t matter if we’re talking shih-tzus or trial border collies. The tendency is to breed tightly and to breed to the dogs that win.

No one sits back and thinks about what this does to the dog populations in the long-term, because no one is really in it for the long term.  You’re in it to win it.

This means that dogs will continue to lose genes over time.  At the very same time, it will be these breeders who are forcing them down these tight genetic bottlenecks who will say they are improving the dogs.

They might be improving in one sense, but in another, they are impoverishing their animals with each successive generation.

The least obvious way in which they are impoverishing their dogs has to do with the immune system. You can’t see immune systems or the genes associated with them, but by golly, you can lose immune system genes.

The genes associated with the immune system are called the Major Histocompatibility Complex, which are called the dog leukocyte antigen (DLA) system. These genes are very easily lost when one is inbreeding or very tightly line breeding.

Now, in most domestic dog populations, breeders are operating within a closed registry system. These closed registries rarely allow new blood in, and if they do, it will most often be from dogs that derive from the same founding population– so it’s not really a new infusion of genes at all.

Then, you have another nice problem within closed registry systems. They demand that people breed only from the best dogs within that system. So certain winning stud dogs wind up siring a huge proportion of the puppies in each generation. Over time, many of these dogs wind up with very similar paternal ancestors, which means it’s very hard to produce dogs within the breed that are not highly inbred.

So you essentially have a system set up for the destruction of the domestic dog as an organism. Over time, the immune system will continue to weaken, coefficients of inbreeding will continue to increase, and the health and reproductive ability of the dogs will continue to fail.

Do we seriously want dogs to end up here?

Do we think all of these breeds are so unique that we can never allow a gene flow to exist between them?

If we think all of these things are true, then we have to accept the obvious consequence– the total collapse of many breeds.

And this analysis doesn’t even account for the tendency for deleterious and lethal recessives to be inherited in a homozygous fashion as a result of inbreeding.

If we are to be honest about saving dogs,  we need to tell these people who promote this toilet science of blood purity and who sanctify consanguinity that they are very wrong– and what they are doing is ultimately dangerous.

I don’t care if some breeder or some half-assed geneticist says it’s okay.

It’s not okay.

It’s going to destroy dogs.

Someone might get good results from a very tight breeding.

That’s not what I’m talking about.

I’m talking about population genetics and population genetics over time.

If everyone is doing that sort of breeding over a long period of time within a closed registry system, it is guaranteed to fail.

Massively fail.

But the institutionalized fancy and its token prostitute scientists continue to promote inbreeding and make apologies for its use that are so twisting of the actual science of dog biology that one wonders if these people might be closet creation scientists.

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Everything here applies to dogs:


Remember–inbreeding in racing pigeons requires harsh culling.

Inbreeding in dogs for performance requires the same thing.

Most people don’t want to do this– we’re talking dogs, remember– so you’re better off trying to reduce COI.

Even then, inbreeding can be very harmful to immune systems as it reduces the diversity within the diversity within the MHC.

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The real lessons learned from the inbred population of wolves at Isle Royale, Michigan.


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Amur tiger cubs

From the BBC:

Approximately 500 Amur tigers actually survive in the wild, but the effective population is a measure of the genetic diversity of the world’s largest cat.

Very low diversity means any vulnerability to disease or rare genetic disorders is likely to be passed on to the next generation.

So these results paint a grim picture for the tiger’s chance of survival.

The findings are reported in the journal Mammalian Biology.

During the early 20th Century, the Amur tiger was almost driven to extinction, as expanding human settlements, habitat loss and poaching wiped out this biggest of cats from over 90% of its range.

By the 1940s, just 20 to 30 individuals survived in the wild. The new study has identified that this recent “genetic bottleneck” – when the breeding population of tigers was so critically low – has decimated the Amur tiger gene pool.

A more genetically diverse population of animals has a much better chance of survival; it is more likely, for example, to contain the genetic resistance to a variety of diseases and less likely to succumb to rare genetic disorders, which can be “cancelled out” by healthy genes.

Scientists in Russia, Spain and Germany worked together to analyse DNA samples from 15 wild Amur tigers in the Russian Far East.

They took blood samples from the animals and screened them for certain “markers” – points in the DNA code that show that an animal had parents that were genetically very different from each other.

The results revealed evidence of the genetic bottleneck during the tigers’ recent history, when the variety of genes being passed on dramatically reduced.

Genetically speaking, the Amur tiger has not recovered from this.

“Our results are the first to demonstrate a quite recent genetic bottleneck in Siberian tigers, a result that matches the well-documented severe demographic decline of the Siberian tiger population in the 1940s,” the researchers wrote in the paper.

“The worryingly low effective population size challenges the optimism for the recovery of the huge Siberian cat.”

Amur tigers are what we used to call Siberian tigers until we learned a bit about Russian geography and learned from the Russians that these tigers aren’t actually found in Siberia.

They may have existed in Siberia at one time, for it turns out that the extinct Caspian subspecies was actually a western population of Amur tigers. Siberia would lie between the ranges of the population from the Caspian Sea region and the population that currently exists in the Russian Far East. It is likely that some tigers did range into parts of Siberia at one time.

The problem isn’t just the deleterious and lethal recessives that are mentioned in this post. The old bugaboo of inbreeding depression looms high, for most cat species do not have very high inbreeding tolerance.

Tigers are also somewhat susceptible to canine distemper.  And Amur tigers commonly hunt dogs that belong to hunters and trappers operating in the region.  Most dogs in the region have not been vaccinated for distemper, which means very bad things for tigers.

My little hope that one day we might be able to restock the Caspian tiger using reintroduced Amur tigers has been fully destroyed. Every Amur tiger is a precious individual, and we can’t risk any of them, even if it is to revive their former western population.

Unless a crossbreeding program can be implemented, as was done when Texas cougars were introduced to Florida panther range, the future is very bleak for the Amur tiger.

And because all other extant tiger subspecies are both critically endangered and native to more or less tropical or subtropical environment, I don’t know how such a program could be implemented practically.

I guess it’s time to enjoy the world’s largest cat while it still lasts.

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Inbreeding Mistakes VI


Winner of the 2010 World's Ugliest Dog Contest was this inbred Chihuahua.


The series continues at BorderWars.

We just don’t know how many diseases dogs could potentially have.

I don’t think the domestication process and the years of rather hard times with us have culled that many deleterious recessives away. If anything, they have meant that natural selection no longer acts upon dogs, and these recessives can continue to exist.

Genetic disorders caused by deleterious recessives are not rare.  One study found that one in four AKC dogs had some sort of genetic disease or defect.

That’s much higher than it is among humans.

If the brilliant Bruce Cattanach had said the same thing about Syrian hamsters, I would be in total agreement. Syrian hamsters have almost no genetic diseases, and the ones available on the pet market are all derived from a single female and her litter that were captured near Aleppo in the 1930’s.


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