Now renowned as a steady family pet, the labradoodle was invented in the 90s to be a low-allergen seeing-eye dog. The breed’s recent origin and portmanteau name makes it rather obvious that labradors and poodles were blended in the creation of the labradoodle. But what about the other 400 or so dog breeds – how does a wolf become a pomeranian?
The origin of modern dogs lies tens of thousands of years ago (somewhere between 20,000 and 40,000) when humans domesticated an ancient relative of today’s wolves. People have been carrying out deliberate, selective cross-breeding since then, initially creating dogs to specialise in herding, hunting and guarding.
Then came the Victorian breed explosion. In the mid-18th century there was a period of intense innovation and codification in dog breeding, giving rise not only to a diversity of breeds, but the very concept of “breed” itself. During this boom, disparate dog lineages were deliberately crossed to enhance favourable traits or dilute undesirable ones. Crossing was also done with the express purpose of creating novel breeds, selecting for aesthetic characteristics.
This created a messy, intertwined relationship between different dog types, with the details of a breed’s origin sometimes recorded only in oral history.
It wasn’t until a landmark genetic study was published in 2017 that we gained a clearer picture of how all these breeds relate to each other.
Researchers from the National Human Genome Research Institute in the US analysed DNA from 161 breeds to create a dog-breed family tree. The tree groups breeds into categories according to their shared history. These groups, known as clades, reflect the fact that for much of their domestication history dogs were known only by the kind of service they offered humankind. The hunting dogs are a family including retrievers and setters, the herding dogs contain the shepherds and sheepdogs.
Dr Elaine Ostrander is the head of cancer genetics and comparative genomics at the institute and was the supervising researcher on the 2017 study, as part of the NHGRI’s dog genome project.
“What we wanted to know was, how do dog breeds relate to one another?” she said.
“We know most breeds have only been around since Victorian times. There were fanciers in Europe who wanted to create breeds that had a particular appearance or have a particular skill or personality.”
Many of the relationships make some intuitive sense, she said.
“One of the things that is important is geographical location – where the breeds were developed,” she said.
“Function was certainly important as well, and there certainly is a relationship among dogs with the same appearance, like the miniature and standard schnauzers.
“But there are always surprises, things that we might not expect.”
The study also presented analyses revealing the shadows of cross-breeding hiding in modern “purebred” dogs.
While the genomes of all dogs are 100% dog DNA, a small amount of the genome varies among breeds. These parts are responsible for the impressive spectrum of variation in size, shape and behaviour in domestic dogs. The researchers sequenced dog genomes at thousands of these variable sites. When blocks of them are identical across two different breeds, this indicates historic interbreeding between them.
These fresh results confirmed documented histories for some breeds. Heidi Parker, the lead researcher on the study and also a geneticist at NHGRI, said the results also showed evidence of crosses that were not documented or were otherwise unexpected.
“We found out that the German shepherd was pretty much Italian,” she said. “I don’t know if we know what the German shepherd story actually is yet, other than it’s one of the breeds that shows up with the most outcrosses to various things.”
Here we’ve used the data from the genetic study to visualise the relatedness between a single breed and all the other breeds they examined (where the relatedness was over a certain threshold – see the notes below for more details):
In this example, you can see the German shepherd shares larger amounts of DNA with the cane paratore, berger picard and chinook. It’s important to note that these graphics do not indicate the direction of the cross – only that two breeds are more or less closely related.
“We don’t know the directionality, it just tells us there has been mixing and matching between breeds,” Ostrander said.
In some cases, much older breed histories were able to be confirmed. A beast of legend, the original Irish wolfhound, had not been seen for almost 100 years and was presumed extinct. In the 1860s George Augustus Graham set about recreating it from existing dog lineages, starting with Scottish deerhound stock and sprinkling in some great dane for added size.
The results for the pug – originally from China – were surprising. Breeders have sprinkled a dash of pug genes into a wide variety of breeds throughout the world, presumably to make them smaller.
Here you can select any breed included in the study to view the relatedness to other breeds, or try one of the groups to see a bigger picture of connections between breeds.
One thing that’s missing from this analysis are so-called “designer breeds”, such as the goldendoodle or groodle, cavoodle and various other -oodles.
The reason for this is, according to Parker, that most of these dogs are not an ongoing breed.
“Most of those breeds, almost all of them, are created simply as one-offs. But they don’t continue,” she said. “The only group that’s really doing that is the labradoodles – the Australian labradoodle club.”
The NHGRI dog genome team has researched the labradoodle specifically, showing it is genetically more poodle than labrador.
Some dogs in the study, such as the dachshund or grey wolf had no links to other breeds. Parker said there are a few possible explanations for this.
“The sharing that we identified in the paper was about 200 years old or less. A couple of the breeds, like the dachshund and Dalmatian, show no bands of sharing at that age point,” she said.
“This could mean that these breeds were set in their current form before that time and no one has seen fit to play with that form. It is also possible that we just don’t have the correct breeds in the dataset to see other additions.
“That is one of the reasons we are still adding more breeds and especially regional breeds to our tree, to fill in the missing pieces.”
As for the future of the dog genome project, Ostrander says they are doing the same analysis between different breeds, using full genomes for comparison.
“One of the questions we’re dying to know the answer to is: what are the differences? What do you see that you didn’t see before with this much higher level of resolution?”
- The dog genome project is interested in collecting more samples from interesting or exotic breeds of dogs. You can email andrew.hogan@nih.gov to see if your sample might be useful in future research.
Notes and methods
Groups used in the figures are the 23 clades given by Ostrander et al’s analysis, with clade-less breeds grouped into “other”.
Colours are mostly to indicate whether two dogs are in different clades, rather than to identify the specific clades as it’s very difficult to make a categorical colour key work with 23 colours.
The relatedness index simply uses a scale from 1 to 100 based on the smallest base-pair size match to the largest basepair size match. Only matches over 250,000 base pairs are included as in the original article.
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