# Diversity Goes to the Dogs **URL:** \ **Category:** Factual Questions\ **Created:** [April 26, 2012, 2:46pm UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019 "2012-04-26T14:46:42Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Sailboat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sailboat/32/461_2.png) [@Sailboat](https://boards.straightdope.com/u/Sailboat)\ **Post date:** [April 26, 2012, 5:54pm UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/21 "2012-04-26T17:54:14Z")
We’ve [discussed this before](http://boards.straightdope.com/sdmb/showthread.php?p=12946894&highlight=mutation#post12946894). > [@](#): > > The researchers noticed something fascinating: specific regions in the dog’s long strings of DNA code that are prone to mutation, called tandem repeat sequences. These tandom repeats are like a single word repeating many times within a sentence, for example, A-C-A-C-A-C-A-C-A-C. They have identified what they believe to be a genetic mutation mechanism that is responsible for the dog’s rapid evolutionary changes. > [@](#): > > Researchers concluded that mutations occurring in these tandem repeats explain why we have been able to change the dog from generation to generation so easily. Two factors are primarily at play. First, mutations in tandem repeat sequences occur much more frequently than in other areas of the DNA–up to 100,000 times as often–and are much more likely to result in significant morphological changes (or changes in physical appearance) in the organism. Second, while all living things have tandem repeats in their genes, the dog has significantly more than most. The above article says “tandem repeat sequences” in the genetic code mean dogs mutate faster than most other mammals. A more scholarly article, [Elevated Basal Slippage Mutation Rates among the Canidae](http://jhered.oxfordjournals.org/content/98/5/452.full), expands on this: > [@](#): > > Previous analysis of tandem repeats in coding regions of developmental genes revealed fewer interruptions in repeat sequences in dogs than in the orthologous repeats in humans, as well as higher levels of polymorphism, but the fragmentary nature of the available dog genome sequence thwarted attempts to distinguish between locus-specific and genome-wide origins of this disparity. Using whole-genome analyses of the human and recently completed dog genomes, we show that dogs possess a genome-wide increase in the basal germ-line slippage mutation rate. Building on the approach that gave rise to the initial observation in dogs, we sequenced 55 coding repeat regions in 42 species representing 10 major carnivore clades and found that a genome-wide elevated slippage mutation rate is a derived character shared by diverse wild canids, distinguishing them from other Carnivora. A similarly heightened slippage profile was also detected in rodents, another taxon exhibiting high diversity and rapid evolvability. The correlation of enhanced slippage rates with major evolutionary radiations suggests that the possession of a “slippery” genome may bestow on some taxa greater potential for rapid evolutionary change. I’m not technical enough to understand whether “basal slippage rate” is simply another term for “tandem repeat sequences,” or a _second_ factor that amplifies the effect of “tandem repeat sequences,” and makes them _even more_ susceptible to rapid genetic change, but **the short version is, there is indeed something special about dogs/wolves, _that predates domestication_, that predisposes them to genetic variation.** ---
**Author:** ![Scupper](https://avatars.discourse-cdn.com/v4/letter/s/b9bd4f/32.png) [@Scupper](https://boards.straightdope.com/u/Scupper)\ **Post date:** [April 26, 2012, 6:32pm UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/22 "2012-04-26T18:32:26Z")
> [@TriPolar](#): > > I guess that could be true if you assume all mutations and variations of genetic composition can be reconstructed from breeding, and modern wolves contain all the genetic components that were in the wolf population at the time of the earliest divergence. With the first assumption you could eventually breed a St. Bernard from a fish. Given enough time, couldn’t you? Maybe not a Saint Bernard per se, but an animal wholly unlike the fish. ---
**Author:** ![Ulfreida](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ulfreida/32/8014_2.png) [@Ulfreida](https://boards.straightdope.com/u/Ulfreida)\ **Post date:** [April 26, 2012, 7:21pm UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/23 "2012-04-26T19:21:29Z")
Biologist Raymond Coppinger convincingly posited the hypothesis that wolves “domesticated” themselves long, long before humans did any conscious selection. Wolves became dogs originally by choosing to hang around human settlements and eat food waste and feces rather than doing the wolf thing of hunting in packs. All dogs have much less cranial capacity than wolves (brains are calorically expensive and garbage doesn’t need a lot of brains to hunt down). If you check out what the commensal dogs, aka pariah dogs look like worldwide, you’ll see there is physically much less of a jump to modern selected dog breeds than from wolves. Another thing: breeds that are selected for a physical appearance that leads to winning in the show ring can get bizarrely exaggerated very quickly, since that venue rewards exaggeration. The appearance of many breeds is very modern. If you compare dogs of a breed now and fifty years ago, you’ll see what I mean. Dwarfy dogs had real legs, smashed-in face dogs could breath normally, dogs that now have endless hair had normal coats. A generation is as short as two years, so concentrated effort in a single direction by a group of breeders can make a remarkable change. ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [April 26, 2012, 7:30pm UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/24 "2012-04-26T19:30:39Z")
> [@Victor\_Charlie](#): > > But two cocker spaniels will always produce cocker spaniels. Only if you define the puppy from two cocker spaniels to be a cocker spaniel. There is natural variation in litters, often enough to produced offspring that aren’t close representatives of the breed. ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [April 26, 2012, 7:51pm UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/25 "2012-04-26T19:51:01Z")
> [@Telemark](#): > > Only if you define the puppy from two cocker spaniels to be a cocker spaniel. There is natural variation in litters, often enough to produced offspring that aren’t close representatives of the breed. Right, it takes endless culling of puppies that don’t conform to the breed standard to maintain the breed. Usually it’s not thought of as “This puppy is not a cocker spaniel” but rather “this puppy is a bad cocker spaniel”. ---
**Author:** ![Kimstu](https://avatars.discourse-cdn.com/v4/letter/k/ecd19e/32.png) [@Kimstu](https://boards.straightdope.com/u/Kimstu)\ **Post date:** [April 26, 2012, 8:13pm UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/26 "2012-04-26T20:13:34Z")
> [@Ulfreida](#): > > Biologist Raymond Coppinger convincingly posited the hypothesis that wolves “domesticated” themselves long, long before humans did any conscious selection. Wolves became dogs originally by choosing to hang around human settlements and eat food waste and feces rather than doing the wolf thing of hunting in packs. All dogs have much less cranial capacity than wolves (brains are calorically expensive and garbage doesn’t need a lot of brains to hunt down). Interesting to speculate what the outcome might have been if this evolutionary tactic had occurred not in wolves but some other wild mammal species. Would we now have a millennia-old tradition of pet pigs? Working pigs, companion pigs, lap-pigs, show pigs? A boy’s best friend is his pig. A piglet is for life, not just for Christmas. Do you know that there are some cultures that actually **eat** pigs? :eek: _GROSS!!_ Now I’m wondering how biologists reconstruct the domestication of our other most common pet species, the cat. Did wild cats “self-domesticate” with prehistoric human societies in something of the same way? ---
**Author:** ![Victor\_Charlie](https://avatars.discourse-cdn.com/v4/letter/v/7ea924/32.png) [@Victor\_Charlie](https://boards.straightdope.com/u/Victor_Charlie)\ **Post date:** [April 26, 2012, 8:31pm UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/27 "2012-04-26T20:31:04Z")
> [@Telemark](#): > > Only if you define the puppy from two cocker spaniels to be a cocker spaniel. There is natural variation in litters, often enough to produced offspring that aren’t close representatives of the breed. That’s certainly true, but the example was in response to a post about dwarfism in humans. Generally speaking, two cocker spaniels will produce dogs that most would recognize as cocker spaniels. The traits of a cocker spaniel are genetically consistent. It’s rare that a pup would be so divergent that it would look like a different dog entirely. You certainly couldn’t breed two cocker spaniels and get a German shepherd (or a dog that looks like one.) Human dwarves, on the other hand, are no more likely to produce dwarf offspring than non-dwarf humans. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [April 26, 2012, 8:47pm UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/28 "2012-04-26T20:47:49Z")
> [@Scupper](#): > > Given enough time, couldn’t you? > > Maybe not a Saint Bernard per se, but an animal wholly unlike the fish. Yes, since nature did it, it’s conceivable, as I stated in my first post. > [@TriPolar](#): > > But since nature did something like that before, it could certainly happen with large enough populations and the ideal set of environmental conditions over a long period of time. ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [April 26, 2012, 10:29pm UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/29 "2012-04-26T22:29:49Z")
> [@Victor\_Charlie](#): > > Human dwarves, on the other hand, are no more likely to produce dwarf offspring than non-dwarf humans. That’s not true. Achondroplasia is a dominant gene. If you have no copies, you develop normally. If you have one copy, you develop dwarfism. If you have two copies, you die before or just after birth. So if Achondroplasiacs mate, 1/4 of their offspring are normal, 1/2 will have dwarfism, and 1/4 will be stillborn. Achondroplasia when neither parent is affected is caused by mutation, not by carrying the gene. ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [April 26, 2012, 10:32pm UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/30 "2012-04-26T22:32:10Z")
Anyway, the point is, the reason that when two cocker spaniels mate you get offspring that look a lot like cocker spaniels is that most of the traits that cause cockerspaniality are homozygous. If you breed two mutts together, even ones that look a lot alike, you can easily get pups that look very different from each other, because mutts will have heterozygous traits. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 26, 2012, 11:02pm UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/31 "2012-04-26T23:02:37Z")
Wolves, like most wild animals, have a lot of genetic diversity. They’ve got some genes that (all else being equal) would produce large size, and some genes (again, all else equal) that would produce small size. Most wolves will have some of each of these, and so they’ll mostly cancel out, and you’ll get a normal-sized wolf. But some wolves, by chance, will happen to have more big genes than small genes, and end up being larger than the average wolf. Take the largest wild wolves, and breed them together, and you’ll still end up up with a mix of genes again, but one that averages a bit larger than the original population. Keep repeating this process, and you end up with a St. Bernard, almost all of whose size genes are the big ones, and almost none of which are the small ones. So St. Bernards are a lot less diverse than the wild wolves they descended from. Run the process the other way, always selecting the smallest wolves, and you end up with a chihuahua, whose size genes are almost all the small ones. Again, they’re much less diverse. But you can’t breed a chihuahua out of St. Bernards, since the St. Bernards just don’t have the small genes to begin with to select (and likewise, you can’t breed a St. Bernard from chihuahuas). Now, if you (somehow) bred chihuahuas with St. Bernards, you’d end up with dogs with a (very specific) mix of big genes and small genes. Let those dogs breed with each other, and you’d end up with a random variation of sizes similar to what you find among wolves (from which you could, again, breed to very large or very small dogs). ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [April 26, 2012, 11:32pm UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/32 "2012-04-26T23:32:31Z")
You might end up with big wolves and little wolves. So far, no one has ever been able to domesticate a wolf, although I don’t know how intensive the effort has been. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 27, 2012, 6:28am UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/33 "2012-04-27T06:28:03Z")
True, when I said “you end up with a St. Bernard”, what I meant was “you end up with an animal the size of a St. Bernard”. There are some traits common to all dogs that you might or might not end up with, and of course there are traits associated with those breeds that have nothing to do with size, like coat pattern. ---
**Author:** ![KarlGrenze](https://avatars.discourse-cdn.com/v4/letter/k/dbc845/32.png) [@KarlGrenze](https://boards.straightdope.com/u/KarlGrenze)\ **Post date:** [April 27, 2012, 9:10am UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/34 "2012-04-27T09:10:41Z")
[Dogs Decoded, a documentary that talks about some of the issues mentioned here.](http://topdocumentaryfilms.com/dogs-decoded/) Note that if you just let dogs mate and breed at random, you won’t get a wolf back. Instead, you’d get the recognizable yellowish, medium-sized mutt, the pariah dog mentioned upstairs. Per the documentary, they tried to see if they could domesticate wolves. It didn’t work, as the wolf puppies, although tamer than wilder ones, definitely did not behave like dog puppies. The majority of large breed dogs have a mutation in one of their genes that is not present in the small breeds of dogs (a variation in an IGF-1 gene). It has been found (more or less), that dogs probably came from a smallish subspecies of wolf. Although they differences look impressive, selective breeding by humans can have a relatively fast and profound change. One example is bulldogs (as per my “school mascot”, the ugly Uga). If you look at the early Uga, from the beginning-mid century, they look somewhat recognizable as a “bulldog”, but definitely different from the barrel-shaped ugliness found today. If someone has the opportunity to pass by the UGA vet college, and is interested, there is a nice display on selective breeding and skull shape changes, complete with skulls, in one of the main (public) lobbies. The transformation is awesome (and somewhat sad). ---
**Author:** ![Victor\_Charlie](https://avatars.discourse-cdn.com/v4/letter/v/7ea924/32.png) [@Victor\_Charlie](https://boards.straightdope.com/u/Victor_Charlie)\ **Post date:** [April 27, 2012, 1:51pm UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/35 "2012-04-27T13:51:06Z")
> [@Lemur866](#): > > Anyway, the point is, the reason that when two cocker spaniels mate you get offspring that look a lot like cocker spaniels is that most of the traits that cause cockerspaniality are homozygous. If you breed two mutts together, even ones that look a lot alike, you can easily get pups that look very different from each other, because mutts will have heterozygous traits. “Cockerspaniality” I like it. That’s the word of the day. ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [April 27, 2012, 2:09pm UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/36 "2012-04-27T14:09:02Z")
Another point I’ve seen made about dogs, is that they change shape & proportions a lot from puppyhood to adulthood (compared to cats, say). This gives selective breeding more to work with, by selecting for various juvenile traits to be retained until adulthood (or to exaggerate adult ones). Takes ears for example; your “generic dog” starts with floppy puppy ears that turn into upright pointy adult ears; with selective breeding they stay floppy. A cat on the other hand starts out as a kitten with upright pointy ears, and ends up as an adult with upright pointy adult ears; there’s no “floppy ear stage” for breeders to aim for. It’s much faster & easier to breed for modifications of existing traits than it is to hope for a mutation that adds a trait you want to breed for. ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [April 27, 2012, 2:11pm UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/37 "2012-04-27T14:11:43Z")
Some species do seem to be much easier to selectively breed than others. Obviously some factors are the genotype and phenotype variation and proportions in the population. As well as obviously things like litter size and reproductive age making some species more convenient for humans to breed. But we don’t quite understand all the contributing factors, and exactly why dogs are one of the easiest species to breed novel characteristics. ETA: Good point **Der Trihs** ---
**Author:** ![Ulfreida](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ulfreida/32/8014_2.png) [@Ulfreida](https://boards.straightdope.com/u/Ulfreida)\ **Post date:** [April 27, 2012, 2:34pm UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/38 "2012-04-27T14:34:00Z")
> [@Kimstu](#): > > Now I’m wondering how biologists reconstruct the domestication of our other most common pet species, the cat. Did wild cats “self-domesticate” with prehistoric human societies in something of the same way? I seem to remember that domestic cats are descended from a small African wild cat which is naturally easily tamed. Other similar looking small wild cat species, not (the European wild cat is not, for example). I could be remembering this wrong. Miners in the western US used to tame Ringtail Cats, which raccoon relatives, not felids; apparently they are also naturally easy to tame. There are probably a fair number of tamable pet prospects out there in the wild, just some caught on and some didn’t. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [April 27, 2012, 2:39pm UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/39 "2012-04-27T14:39:28Z")
> [@Mijin](#): > > Some species do seem to be much easier to selectively breed than others. > Obviously some factors are the genotype and phenotype variation and proportions in the population. As well as obviously things like litter size and reproductive age making some species more convenient for humans to breed. > > But we don’t quite understand all the contributing factors, and exactly why dogs are one of the easiest species to breed novel characteristics. > > ETA: Good point **Der Trihs** The documentary\*\* KarlGrenze \*\*mentions above (if it’s the one I think it is) along with other references in this thread explain some of the incredible malleability of dog genes. It’s an animal breeders dream to have that much inherent diversity to work with. If you wanted to breed a new form of a cheetah you’d be stuck looking for a significant mutation in animals that are all as closely related as siblings. As \*\*Karl \*\*also mentions, it is suspected that domesticated dogs descended from some sub-species of wolf. It does make sense that humans would start domestication with something a bit different from a gray wolf whose cute offspring are likely to eat your children. But we haven’t been able to narrow down when dogs were first domesticated yet. We may never uncover enough evidence to determine how it all got started. Some anti-evolutionists have tried to justify their steady state idea by claiming that dogs if left to intermix without human intervention would return to the wolf form. But wild dog populations don’t do that, and though I don’t know the details, they’ve probably lost some of the genes that wolves have, or their genes have diverged sufficiently that there’s no path back to the wolf characteristics that would be advantageous to the dogs in their environment. ---
**Author:** ![D18](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@D18](https://boards.straightdope.com/u/D18)\ **Post date:** [April 27, 2012, 4:21pm UTC](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019/40 "2012-04-27T16:21:14Z")
I’ve seen this referenced before on the boards, but as it’s germane to the discussion, here is a cite to the [domesticated silver fox](http://en.wikipedia.org/wiki/Domesticated_silver_fox) experiments out of Siberia. Here’s the story I first read on it from [National Geographic](http://ngm.nationalgeographic.com/print/2011/03/taming-wild-animals/ratliff-text) and one I haven’t read it from [Slate](http://www.slate.com/articles/health_and_science/science/2012/03/domesticated_foxes_in_siberia_an_experiment_in_peril_.html). Bottom line - the study has managed to create two cohorts of foxes - one thoroughly domesticated and one completely vicious toward humans. And they did so in less than a half-century. From the National Geographic story: > [@](#): > > Miraculously, Belyaev had compressed thousands of years of domestication into a few years. Some of the morphology of the domesticated dog may be explained by “a domestication phenotype”. Again, from the National Geographic article: > [@](#): > > Belyaev suspected that as the foxes became domesticated, they too might begin to show aspects of a domestication phenotype. He was right again: Selecting which foxes to breed based solely on how well they got along with humans seemed to alter their physical appearance along with their dispositions. After only nine generations, the researchers recorded fox kits born with floppier ears. Piebald patterns appeared on their coats. By this time the foxes were already whining and wagging their tails in response to a human presence, behaviors never seen in wild foxes. > > Driving those changes, Belyaev postulated, was a collection of genes that conferred a propensity to tameness—a genotype that the foxes perhaps shared with any species that could be domesticated. [Previous page](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019.md?page=1) [Next page](https://boards.straightdope.com/t/diversity-goes-to-the-dogs/620019.md?page=3)