Genetic bottlenecks, environmental pressure, and the development of dog breeds

I read MANY blogs. Somewhere in the range of a couple hundred. News, photography, scrapbooking (to make me feel guilty), and of course animal behavior, sheltering, all the Cardi blogs, legislation blogs, Gizmodo and Freakonomics and Lifehacker and Dooce, etc.

Some I read to keep me honest–Nathan Winograd is good at that.

Some I read because deep down some part of me wishes I lived the life of that blogger–the Daily Coyote comes to mind.

And there’s one I read because after I read his stuff I have to turn off the computer and go stare at the sky. Stephen Bodio is a hawker, a dog owner and breeder, a cattle rancher, a man who has dust in his boots and an incredible amount of deep and true thought in his head.

He wrote recently and touched on a few of the current genetic arguments surrounding dog breeds, which I thought dovetailed neatly into what I’ve been talking about in terms of genetic diversity in breeds. So I’m not going to quote him but I am going to use a few of the example breeds that he brought up.

Breeds as landraces are very, very old. A landrace is just as useful as a breed but it tends to be defined solely by the job it can do and by its environment–if you think about the Border Collie before it was ever registered, you get an idea. Their appearance can vary–if you mean appearance like “show quality” you could say the appearance varies a lot. Some Border Collies are substantially larger, some smaller, some have prick ears, some drop, color and coat type and leg length can vary. But in many other ways they are very similar–most people can still reliably identify them as Border Collies, and they all work in basically the same way.

The difference between a landrace and a breed is that a breed generally has a closed population, where individuals are bred only to other members of that breed. When you’re working with a landrace utility is king–if a dog shows up that kills rabbits really well, you’ll want to keep him around to breed to your other rabbit-killing dogs even if he doesn’t look exactly like them. But he’s unlikely to look totally different from them either, because there’s a certain body type and size and speed that naturally lends itself to successful rabbit killing. So among landraces there is a certain amount of sharing of genetic material–if the rabbit killer also happens to be a decent fox chaser, he may be used by people who like chasing foxes too.

Landraces probably developed along the same lines that dogs became domesticated hundreds or thousands of years prior–the dog wanted it and the human wanted it, and dogs have a tremendously plastic body and brain and from that symbiosis came dogs that were more useful at doing certain dog-human things than their ancestors had been.

So very, very long ago we can see what we think of as the major types of dogs. The Far East pioneered the idea of the dog purely as a companion, and they like the very stylized appearance of the flat-faced small dog, and so the flat-faced companion dog begins to spread along the trade routes coming west. This was happening thousands of years ago–the flat-faced small companion dog is very ancient.

Another group, probably in Germany, liked a type of dog that had very short legs, because short legs enabled the dog to do some things that long-legged dogs could not do. They probably began using them as hunting dogs but when the trade and conquest routes brought the short-legged dogs to other areas where hunting was not the predominant activity that dogs did, the owners of those dogs realized that short legs made some of their activites easier and made those dogs very useful. So, and again this is thousands of years ago, we already have a corgi landrace herding in Wales, a Vallhund landrace herding and hunting in Scandinavia, a Dachshund landrace hunting in Germany, etc.

The earliest true breeds, where pedigrees were maintained and it was understood that you only breed members of that breed to each other, are also extremely old. They grew out of an increased specialization of the landraces, a desire to have greater predictability in terms of exactly how big, small, tall, short, or useful that dog was.

There are only a very few of those true early breeds still around. Most of the breed-origin myths that are droned over the picture at Westminster are romantic fiction. But some of them DO still exist. One is the Sloughi (not Saluki), one is the very primitive Basenji, another is the Chow, and I think the Pekingese makes the list as well.

So the vast majority of the breeds we know today became closed, where individuals were not bred outside the breed, only in the last couple hundred years. It’s important not to therefore conclude that all dogs looked the same before that point, or anything close to that. If you traveled through Europe in 1600, you’d see an incredible number of distinct-looking dogs and probably hundreds of what we’d call breeds. But there was still communication between the breeds, sometimes slight and sometimes heavy.

When identification of breeds and registration of individual dogs, and eventual closing of studbooks, became fashionable in the 1800s, two things happened: Existing breeds were identified and codified and registered, and older breeds that were seen to be in danger of extinction or in come cases had already become extinct were re-created. So the Ibizan Hound and the Pharoah Hound were re-created, as were the Irish Wolfhound, the Elkhound, and many others. It seems unlikely that any of these were created from absolutely nothing; it’s a lot more likely (and certain in a few of them that I know the history of) that people passionate about a disappearing breed or landrace gathered the last remaining members of the population and then bred them to dogs that were as similar as possible to them in appearance and function.

At any rate, we have between 1850 and 1900 a whole ton of breeds being gathered, registered, and from then on bred only to each other.

By the 1930s there are a whole bunch of breeds that have their stud books closed (in other words, no more dogs are ever going to be let in).

Here’s where it gets sticky. In the 1920s and 30s distemper was killing dogs off in huge numbers. And then the advent of World War II and the extreme levels of starvation and hardship in Europe dealt a horrible blow to a large number of dog breeds.

Sussex Spaniels, for example, almost completely died off or were killed. The population dropped to just eight individuals. Shar Peis dropped to incredibly small numbers even more recently, as of the late 1970s. Lundehunds were reduced to six total. Cavalier King Charles Spaniels almost disappeared and were only saved by intense inbreeding in the 40s. Flatcoat Retrievers almost died out as well. The list of breeds that was reduced to only a bare handful of individuals is pretty long.

This is the definition of a genetic bottleneck. If, after the event or environmental pressure that kills off the vast majority of the population is over, no more founding individuals are added, then the entire breed (or, in the case of certain animals like the Asiatic lion, the entire species) becomes an expression of only those six or eight or whatever individuals.

A founding population that is that small is extremely risky. The likelihood that you can develop a genetically diverse and healthy ongoing population from six or eight or twelve already related members is small.

And, in fact, we do see that risk played out in these breeds. Sussex with their low fecundity and heart issues, Cavaliers with heart and brain problems, Lundehunds with mysterious digestive issues and early deaths, Flatcoats with cancers that effectively cut the breed’s lifespan in half.

So we have moved, in most breeds, from a situation of quite a bit of genetic information coming into and leaving the landraces to gene pools that are entirely based on a startlingly small number of dogs and where zero genetic material comes into or leaves the population.

We have effectively made each breed into an endangered species.

I can tell you, from far too many late nights up studing population ecology, that one of the things that is considered an immediate emergency in an endangered species with no available genetic material from the outside is keeping the heterozygosity of the population absolutely as high as it can be. It is considered so critical that the at-risk populations are constantly monitored for COI and also a direct measure of heterozygosity called MLH, and increasing heterozygosity is a key sign that the population has hope and may succeed and survive.

There are very few, if any, endangered species experts monitoring dog populations. That’s because the “dog” is not in any way endangered. Taken across the whole world it’s in great shape. But don’t fool yourself into thinking that individual breeds are not at critical danger of collapse and extinction. Both in absolute numbers and in size of gene pool, there are a strartling number of breeds that should be considered critically endangered. Even in the more numerous breeds, the representation of founding members is extremely poor and the average mating is equivalent to full-sibling.

If we don’t pay attention to this, we WILL pay the price, or the next generation of breeders will pay the price. I don’t know how much more plainly to put this–we’ve been breeding in a way that is very unlikely to be sustainable. And since we’re the ones making the decisions, it’s up to us to do our best to fix it.

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3 thoughts on “Genetic bottlenecks, environmental pressure, and the development of dog breeds

  1. Very well said. I long for the day when we can bring back the Collie landrace and have a diverse and large gene pool of Collie dogs that can subsist on its own or be used as a more successful outcross to the member breeds.

    The problem is that a lot of inbreeding, culling, and highly selective breeding (such as overuse of popular sires) went in to creating breeds out of our landraces, and that was harmful enough. BUT the breeders never stopped. They have never put on the breaks and stopped the techniques that were used at the beginning.

    Sure, if you want an ideal sculpture, you have to cut away some marble, but at some point you need to use smaller tools instead of the big hammer of inbreeding, and when it’s done, it should be one. If you keep wacking away at it, you eventually end up with a pile of rubble, and in a closed registry or even an open one that no one really takes advantage of, you can’t put pieces back after you’ve chiseled them off.

  2. Pingback: Genetic bottlenecks, environmental pressure, and the development … :: doglore.net

  3. I have a friend who has had Dandie Dinmonts for years. It is one of those breeds that seems to be heading for disaster. They are saying it is time to outbreed. Bring in some new genetic material, which will have to come outside the breed; perhaps dachsund. Do you feel that this is the only solution? When the genetic pool becomes so small and phenotype so important is it not a given that health and longevity begins to suffer? I am a firm believer in purebred dogs, but sometimes worry that too many breeders focus on looks rather than performance. There will always be those that just don’t want to know if their breeders are carriers. I am also a firm believer in working breeds being able to work, a herder being able to herd, etc.
    Thanks for the great read. My brain is really racing on this one. And it is still early.

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