Domestic Animal Breeding and Speciation

@gbrooks9, I disagreed extensively with this idea of yours in a thread quite some time ago. So it is painful to see you blithely repeating it in “agreement” with me.

Breeders are not breeding for intervarietal reproductive compatibility. Greyhound racers are breeding for speed and do not care if their dogs can breed with chihuahuas. Shepherds in Scotland are breeding for good sheepdogs, not for the ability to have puppies with Chinese dogs.

If your idea were truly the reason that dogs can still breed with each other, we would see wolf populations that haven’t interbred since the domestication of the dog that are unable to reproduce because they’ve drifted so far apart. Instead, it is the case that the non-fox canids seem to all still be reproductively compatible: wolves, dogs, coyotes, and jackals interbreed just fine.

If you want to discuss this idea further, I suggest we start a new thread, because it is not particularly relevant to Mark’s topic.


Well, for much of the thread, much of what Mark is bringing up doesn’t seem relevant to “reconciling” the two groups and their positions on Evolution.

He was pleading for an answer about why we don’t have new families of Canines erupting from our domestic dog population… and so I responded to his pleadings.

So… @Lynn_Munter, what exactly is your textbook-ready answer for why we don’t find speciation erupting from within our dog breeding cages?

How many Chihuahua breeders make sure their dogs can crossbreed naturally with Great Danes? In fact, are there any examples of a half-Chihuahua half-Great Dane litter? Are they even genetically compatible?[quote=“gbrooks9, post:3, topic:37489”]
He was pleading for an answer about why we don’t have new families of Canines erupting from our domestic dog population…

The reason is that there are no groups of dogs that have been genetically diverging for 10’s of millions of years.

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That’s not what I said. What I said was that the way dog breeders freely mix in dogs of various breeds in order to contribute a desirable trait is a process that inclines the resulting offspring towards continued (if not increasing) reproductive compatibility.

As breeders are constantly crossing breed boundaries, overlapping compatibility extends broadly throughout the domesticated dog population.

I would agree with your point but not with how you word it. The question YECs throw at us is why isn’t there a new species produced from all these exaggerated breeds that humans create. The answer is because the breeding process smoothes over reproductive incompatibilities… rather than accentuating them.

A professional what? Professional dog-breeder? I can tell you that most of them are only interested in breeding ‘purebreds’ whose last eight generations are all of the same breed. They are not breeding for the maintenance of compatibility with other breeds, except inasmuch as they generally want to maintain the ability to breed, period. But then any creature, wild or domestic, that doesn’t reproduce isn’t going to have much future.

You’re barking up the wrong tree with this!

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And that was the point I was trying to make…

I don’t believe we find in any practices of dog breeders anything that would support or encourage speciation…

The process of Speciation would so represent the exact opposite of what their operating goals and practices are, they would literally have to give up their vocation to accomplish it.

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I was under the impression that dog breeders use line breeding (i.e. inbreeding) to isolate wanted traits, and then use a very limited population as a seed population which are the founders for the whole breed. I personally don’t know of any dog breeders that really worry about reproductive compatibility, nor do I see why this practice would lend itself to reproductive compatibility. However, I don’t claim to be a dog breeding expert so I may be missing something. It would seem that any compatibility is happenstance while the main focus of dog breeding is getting to a “pure bred” who is homozygous for the traits you are interested in.[quote=“gbrooks9, post:5, topic:37489”]
The question YECs throw at us is why isn’t there a new species produced from all these exaggerated breeds that humans create. The answer is because the breeding process smoothes over reproductive incompatibilities… rather than accentuating them.

It would seem to me that Chihuahuas and Great Danes are effectively different species, and there would be no genetic transfer between them without the dog breeds in between. This isn’t seen in their wild cousins, the wolf. There aren’t drastic size differences between wolves that prevent interbreeding like there are in domestic dogs.

It would seem to me that humans put up barriers to gene flow between populations of dog breeds. This would tend to favor speciation.

Because they’re just not that different yet. Nobody seriously expects to see speciation occurring in dogs after a mere few thousand years.

Shall we engage in a little thought-experiment? Let’s say an event happens which causes reproductive incompatibility … the number of chromosomes changes, for example. According to your hypothesis, the breeders will observe that the dog has fertility troubles and think, oh, I better not give this dog any more chances to breed, because I don’t want to risk having a dog that can’t create lots of puppies? Whereas I think it’s more likely that they will have any number of other reactions, such as: “This dog is good at sheepherding, I think we should try again to get puppies;” “But my kids would like having puppies, let’s see if we can get some;” “tying up this dog is too much trouble because it barks a lot, if it has puppies with the neighbor’s dog, who cares;” or “I love Fido, I want more just like him!”

Remember that it is insufficient to your case for less fertile dogs to simply reproduce less successfully, because that applies equally to wild wolves and has nothing to do with artificial selection or domestication.

For the vast majority of doggy history, the model of puppy mills where the highest priority is on producing more dogs because people will pay for puppies is not relevant to how dogs actually reproduced. Dogs bred themselves as strays living in and around human settlements, or humans focused on a specific purpose they wanted dogs to accomplish. And even with modern puppy mills, they still usually stick within a breed.

Cross-breed fertility in dogs is a neutral trait, as far as I can see, neither selected for or against except for the general tendency of fertility to be selected for.

I will note that dogs are more fertile than wolves in a couple respects, in that wolves restrict their breeding seasonally and to when they have a stable pair-bond, to ensure that they have the resources to successfully raise young, while dogs need not factor in such things because humans feed them more reliably, so they can breed at any time of the year and with any partner they just met and still likely raise the litter successfully. But this doesn’t mean humans deliberately bred for this, either.

The English Bulldog is an interesting case. Breeders have gone so far overboard in selecting for face and jaw traits that Caesarean sections are now becoming common in order to even birth the pups. On top of that, bulldogs can have serious health issues due to the traits that have been selected which reduces their ability to breed.

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Dogs were once bred mostly for function–they worked for their owners. Sled dogs had to pull hard and live in extremely cold weather. Herding dogs had to be tireless and not attack the sheep they were herding. You will notice that they exhibit the stalking behavior of predators (freezing, stalking) but don’t go in for the kill. Bird dogs take it a step further. They “freeze” (point) when a bird is spotted, do not stalk, and don’t move until told to do so. And so it goes, with guard dogs, companion dogs, etc. It is only relatively recently that most breeders (AKC ones, anyway) have been going predominately for appearance, where health and function is of secondary importance. And you often end up with inbred and unhealthy dogs. Just look at brachycephalic breeds with the squashed faces, struggling to breathe.

And speaking of dog breeding, all English bulldogs are bred via artificial insemination. When a male bulldog tries to mount a female she collapses!


I have to agree that it would be quite illustrative if someone crazy scientist did a study on Great Danes vs. Chihuahuas!

Currently, I would expect many people just assume that if a mating pair of these two breeds could “figure it out”, we would expect litters to be directly forthcoming! But would they? I confess that I have just followed along with the general proposition… but if some kind of testing was done that actually showed that these 2 breeds were actually less than averagely compatible (in the sense of fertility), such a result would actually be consistent with the general idea that it is common and/or frequent inter-breeding that maintains dogs’ generalized reproductive compatibility - - compromised only when the physical differences between the hoped for pairing Trumps all other considerations.

For those who find my thesis generally objectionable … since the idea that the considerable exertions of human energy dedicated to cross-breeding dogs is not likely to have zero affect on breed reproductive capabilities… we should be inclined to expect a result opposite to my hypothesis: that cross-breeding most likely exacerbates the reproductive incompatibilities between breeds.

Could we have a more distinctive choice?

I think most of us agree that what promotes Speciation is moving along a gradient of decreasing exchanges of genetic information between sections of a population. That doesn’t seem to be very controversial.

But the general ruckus that ensues as soon as anyone tries to extrapolate from that position that exuberant campaigns to cross-breed striking traits from one section to a second section of the domesticated dog population, probably - - over time - - contributes to the opposite of Speciation within the domestic dog population, doesn’t seem to be following the line of the discussion.

If you want to create a ring species, you reduce the exchange of genetic information between sub-groups. If you want to avoid the formation of a ring species, you would intentionally exchange large pockets of genetic information between any number of sectors of the dog population. And even though “breeding” typically involves restricting free sexual behavior, that is only for the final “end product” - - the perfected breed. Unless there is a system of euthanasia to eliminate all the “half-way bred” dogs… and the inevitable trajectories of genetic information created by the resourceful genius of many a canine … there would be quite a bit of genetic blurring amongst the “peasant” dog population!

I found this (ETA: as you will see not far downthread, this article is probably not true):

Of course, the amount of effort is surely comparable to anyone futzing about with cross-species hybrids like wolphins and ligers.


A young wolf can disperse hundreds or thousands of miles away from their home territory to find a mate in a single generation. How do the “exuberant crossbreeding campaigns” compare to the amount of genetic exchange that happens naturally in the wild?

This is very, very suspicious and my baloney detector is overheating. Believe me, the American Kennel Club is not part of this. (And the mating probably never even occurred.) For one thing, when you cross two different breeds of dog you get a “designer breed” (e.g. Labradoodle), not a true purebred dog. If you breed two labradoodles together you won’t get a litter of puppies that all look like labradoodles (because of genetics)!

To develop a real breed, some inbreeding is required, and this inbreeding also explains why purebred dogs can have bad health problems.

@beaglelady Fair. I never really thought it was at the point of breed status but I’ve seen in other places that attempts have been made. I can see if I can find anything more reliable.

ETA: looks like you’re not the only one.


I don’t believe you had a rational position for your objections.

While I have since added some more narrative to help explain my position.

Speciation is all about the continuum of Reproductive Compatibility.

There is a reason why we have hundreds and hundreds of phenotypes … with no apparent changes in reproductive compatibility.

I think you will need to bring in a professional on this one. Maybe he or she can engage some additional concepts in a refutation.

Because your objections didn’t make any sense to me then, and I was hoping you had dropped them in the intervening time.


You can find what you want on Google. Especially if it isn’t true.

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Speciation is all about the splitting of one species into two different ones.

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I’m not sure your hypothetical relates well to the topic I’m discussing.

For example, the topic of Ring Species frequently deals with populations of animals advancing into territory (or continuing to hold territory) that bends around a natural barrier (say, a mountain, or a bay).

The exchange of genetic material is summarized at the population level, rather than at the ultimate range of a single individual.

I’m sure there is a fancy field of mathematics that would help visualize this. But essentially the exchange of genetic information is between members of a subgroup that are closer to each other than is the distance between neighboring subgroups.

In an extended range that circles around mountain, or a canyon, or body of water, intra-subgroup exchange is high, while inter-subgroup exchange is low. And should an average individual from one of the the two terminal ends of the entire chain of subgroups attempt to mate with an average individual from the other terminal end of the range… mathematically we would expect there to be less reproductive compatibility, simply because the effects of genetic drift become that much more significant than the amount of genetic exchange (which could still be going on at a low level) between the two terminal subgroups.

In view of this description, I think you can see, @Lynn_Munter, that the lone wolf scenario is perfectly fine - - just not applicable to the question at hand.

As to the “exuberant crossbreeding campaigns” that I mention… let me provide a rough image of how I visualize the matter… it is far from complete… but it is the start of a master chart representing approximately 525 million dogs believed to be living on Earth today, divided into 339 Breeds, aggregated into 10 major categories of Breeds (as recognized by the World Canine Organization, and leaving all else as either Mutts or Cur), and 60 Regional Types.

In the picture below, the X Axis is 2 regional types x 30 columns, while the Y Axis has 10 rows for the categories and an 11th row for Mutts/Cur. This visualization may turn out to be a dead end. But what I will hope to show with it is that generations of Breeding programs, overlapping various chunks of breeds and regions, over time, should well have touched every obscure kind of domestic dog one can imagine.

Even though a breeder is trying to restrict the genetic scope of his breed, that is only after the breed is established. To build a breed, sometimes the breeder has to bring in genetic contributors from another chunk of the domesticated dog population.

Then there are the dogs that don’t make the cut. Does he euthanize them? Or does he give them away? Over centuries of time, I’m thinking all this activity is more like a Cuisinart blender at the Mutt-End of the spectrum, with the ultimate result being a very robust reproductive compatibility between the various corners of the dog population - - rather than a pattern of dogs that are not able to breed well with each other (setting aside obvious physical limitations like giant Greyhounds vs. Corgies).

Anecdotally, at the very least, I have never heard of any dog lover or dog breeder talking about how some breeds just can’t produce pups… which would be a “flag” that there are pockets of reproductive incompatibility.

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