All About Outcrossing – Part I

Merriam-Webster’s definition of the word outcrossing is this:

“the interbreeding of individuals or stocks that are relatively unrelated”

This is a pretty tame definition for all the furor around the idea in dogs! Some people are adamantly opposed to outcrossing, and some think it’s the only way forward.

This divide is largely due to a difference in schools of thought – because the actual practice of outcrossing is quite broad. The definition contains the reason for that breadth – it’s the word “relatively.”

Two different lines are relatively unrelated. Two different breeds are relatively unrelated. Two different types of dogs are relatively unrelated. Two different species are relatively unrelated. So really what are we talking about here?

We are talking about concepts and how they are often conveyed in one way and perceived in another way.

Talking to our dog show/agility/breeder friends, outcrossing means finding another line not like our own, but likely one within the style of dog we prefer and for-heaven’s-sake certainly within the breed.  And there is nothing wrong with this definition of outcrossing. It fits the definition.

If we are talking to people who are largely convinced that inbred breeds are the cause of all purebred dog problems – and there are fewer of these people, but they are louder – then outcross means crossing to different breeds. Often in this case, they consider the more different the breed, the better the outcross – kind of the opposite of what the group mentioned above would consider. Yet this too fits the definition.

For the last decade or more, amplified by the 2008 documentary Pedigree Dogs Exposed, there has been a quiet movement afoot to address the instances of two big problems in dogs: breed specific disease and dysfunctional phenotype. They are not one and the same, but they do have common causes. Some breeds have one problem, some have the other – some have both. The attention brought to these issues and the subsequent blame placed on breeders for causing them have become enormous public relations problems for purebred dog breeders. That negativity has also fueled the “adopt don’t shop” movement started by animal rights activists.

Pedigree Dogs Exposed was a British production and had an unexpectedly activist tone for the American audience, which at the time was more accustomed to documentaries that were more straight, objective reporting, and not opinion. In response to the film, the British Kennel Club made certain mild steps toward reforms, though those are a subject for another discussion. In the US, rather than address the legitimate issues addressed by the film, its aggressive, blaming tone split communities in two. Some breeders retreated further into their traditions while others clamored, rather generally, for more diversity. Some even capitalized on the idea and berated dog breeders for their practices, alienating many more and gathering ardent followers as well. Ten years on, some breed communities have made a lot of progress, and some haven’t. There are still little skirmishes about who is right and who is wrong, who is bad and who is good, but unfortunately, none of the squabbling adds up to dogs living longer healthier lives.

By now you are asking, “What does this have to do with outcrossing?” Everything.

The prime culprits identified in Pedigree Dogs Exposed were breeder culture and more particularly, systemic inbreeding.  Of course inbreeding is part of breeder culture in a sense, since linebreeding is the fastest, most widely taught way to get to certain desired phenotype – or appearance – possible. But it’s also tradition, and dog breeders generally have no problem with it, while outside breeder culture inbreeding is seen the same way it would be seen in humans – distasteful at best and dangerous at worst.

The truth is that inbreeding is not really that much of a problem – until it is. In other words, it’s not inbreeding in individual cases that’s the problem, it’s systemic inbreeding over many generations on the same ancestors that wreaks havoc. If a whole breed community is inbreeding on the same popular sire or his sons or close family, eventually there will be a problem. That’s because all dogs carry some negative mutations – and most of them are never a problem unless two copies of the mutation end up in the same dog. This typically only happens when the same ancestor appears on both sides of the pedigree. The more times that ancestor appears on both sides, the higher the chances of descendants inheriting two copies and with two copies in simple recessive diseases, th dog gets a disease. That’s why some breeds have particular diseases other breeds never get – because they were singular mutations in one of the founders or a popular sire that appeared after the breed was founded.

Inbreeding can also cause a high frequency of more complex diseases for similar reasons, but these complex diseases are caused by a number of genes that interact instead of a single one. They also can become more and more common in specific breeds when the whole breed is built on a few founders – depending on which genes the founders had. That’s not a one-time inbreeding issue – it takes many generations of breeding dogs with the same ancestors to see the problem and by then it is widespread. This is why even severe inbreeding seemed to work just fine for breeders for many generations – it takes a long time till all dogs in a breed are very similar. Systemic inbreeding is what hastens that. These diseases are harder to find a usable DNA test for or to breed away once they are really common in a breed.

Inbreeding can exist in a breed in a less harmful way, but only if the population consists of many inbred but different lines that retain general good health across the breed population. In this case, average inbreeding in the breed may be high, but it’s not systemic inbreeding because there may always be a good – you guessed it – OUTCROSS available within the breed to allow breeders to breed away from a problem.

You can’t fix inbreeding depression by vacuuming a genome free of mutations. There will always be more because DNA mutates.

The other thing systemic inbreeding can do is create extreme phenotype or traits – and sometimes those traits become dysfunctionally extreme. If a dog is supposed to be long and low, some breeders may make them extremely long and low – which can cause vertebral problems. If they should have big heads, the heads can become so big that natural birth is difficult. If skin should be loose, it can become so loose that it doesn’t get enough air in the all the wrinkles and skin diseases develop. If the shape of the head should be short – it can be so short as to cause neurological problems from not having enough room for proper brain growth, and if the muzzle should be short, it can be so short as to cause automatic airway disease. None of these are or were ever breeders’ intentions, but they do happen. This becomes a major issue when dysfunctional traits are largely “fixed” in a breed – where all the dogs have those genes. Then there aren’t any dogs left with longer muzzles that can lengthen a too-short muzzle, or normal sized skulls that will mitigate too-small or too-large ones, or dogs with tighter skin to improve on too many wrinkles,  or squarer dogs that can modify too-long backs. Once the genes for the more moderate shape is bred out of a breed entirely, the only way to get it back is to – you guessed it – OUTCROSS.

So now of course, since the idea of breed specific disease, dysfunctional phenotype and inbreeding have become more and more well known, some in the dog world have clamored for OUTCROSSING. Some, having been told all purebred dogs will soon be extinct, want to outcross everything immediately. This is poppycock. Their “opponents” say it’s more important to keep the “essence” of the breed and instead look for the mutations that cause disease, since there are almost always some dogs which don’t experience the worst effects of a problem – and that, frankly, is what many breeders most want to hear, but it’s also, sadly, poppycock. You can’t fix inbreeding depression by vacuuming a genome free of mutations. There will always be more because DNA mutates.

So what can we do?  First, it’s important to acknowledge that breeds are unique and they each need a different approach to maintain existing diversity or respond to their current status. It’s also important to acknowledge that there is no lack of diversity in dogs – canis familiaris – their genetic diversity is simply highly segregated into many subpopulations. Anytime someone wants to “restore” a breed, it can be done – and yes the restoration may change a breed somewhat, but, then, so will extinction. Eventually, we will all have to learn to manage our breeds well, or pick our poison in outcrossing. But first we have to know whether our breed is really in trouble, and if so, how much, and of which kind.

That doesn’t take long and it’s relatively inexpensive. What it does require is a few serious, knowledgeable breeders who want to step up and be breed conservators.

Part II coming soon.