The First Merle Dog
The First Merle Dog By: Liisa Sarakontu
As published in ~Merle - SINE Insertion from Mc - Mh - The Incredible Story of Merle~ ©2021
It is often asked what is the real history of the Merle mutation in dogs, where did it first happen and what modern breeds do have Merle "naturally". All of this isn't fully known, but let's go through some known facts.
What is the Merle mutation?
The Merle mutation happened when a certain part of virus RNA attached itself to just certain spot of dog DNA. There are other cases of virus RNA attaching to mammal DNA, but the chances that JUST the very same part of certain virus RNA would attach itself to JUST that special spot in dog DNA are basically zero. Merle is such a weird and rare mutation that it has originally happened just once. Another mutation causing a similar looking coat pattern could happen, but it wouldn't be testable with the same Merle test which exists now. All Merle dogs in all breeds ever tested after the test was finished test positive for Merle. Another rather similar mutation wouldn't test positive as this test looks just for certain mutation. Just like there are now about five known b type mutations in B locus causing black eumelanin pigment turn into brown, and each of those mutations requires a separate test.
The Merle mutation really has happened only once in the history of dogs, and all Merle dogs living today are descendents from that one mutant individual.
When did the Merle mutation happen and where?
There are no real documents when the Merle mutation really happened. It happened for sure over 150 years ago, as closed stud books were started around 1880, and there were Merle dogs in many of the newly created "pure breeds" which were based mainly on local landrace working dog populations. If the mutation would have happened after that year, there would have been Merles in only one or very few breeds and only in one geographic location. There are also paintings showing clearly Merle patterned dogs from early 19th century.
The Merle mutation can't be as old as domesticated dog as the pattern is missing from landrace and local populations in most parts of the world, unlike such ancient mutations like recessive yellow (e/e) or dominant solid dark (KB), which are spread basically everywhere. When looking at breeds which traditionally have Merle, it is certain that Merle happened in Europe, likely in central or western Europe, and during a time when dogs were already more than "just dogs", when they had specific work to do. It may have happened a few hundred years ago, perhaps 250-500 years, either in herding dogs or in hounds. Not in a certain breed, as it has happened before there were what we now think of as "purebreds".
Which breeds have merle naturally?
All breeds which have Merle have it naturally, a pair of dogs have bred and as one parent was Merle, some of the offspring are also Merle. Nothing non natural has happened, like artificially triggered mutations or gene transplanting. The real question is which dog breeds with closed stud books have had Merle traditionally from the start of the stud book, and which have gotten it later through non recorded crossbreeding.
Most of the traditionally Merle breeds belong to the herding breeds. These dogs were exported all over the world with European settlers. Traditionally Merle herding breeds include Border Collie, Rough Collie, Smooth Collie, Shetland Sheepdog, Welsh Sheepdog, Welsh Corgi Cardigan, Australian Shepherd Dog, Australian Koolie, Pyrenean Shepherd, Altdeutsche Hütehund, Bergamasco and Apuan Shepherd. Merle might have existed in Old English Sheepdog, but it seems to be missing from the modern gene pool of that breed. Merle is missing from all spitz type herding dogs and livestock guarding dogs.
The only traditionally Merle normal hound breed today is Norwegian Dunker Hound, which must have gotten its Merle in first half of 19th century from Russian Harlequin Hound, which is mentioned as a forefather of several Nordic hound breeds. The modern Russian hound breed Anglo-Russian Hound is also called Russian Harlequin Hound, but there are no Merles in that breed, which was created by crossing older Russian hounds with imported English Foxhounds during 18th and 19th centuries. Dachshund is also basically a hound breed, and it has had Merle (called "dapple") since stud books were closed.
Other traditionally Merle breeds are Great Dane, and harlequins in that breed are also Merles. Merle in this breed comes more likely from hounds than herding dogs. Beauceron likely got Merle (called "harlequin" or "arlequin" ) from herding dog roots. Harlequin Pinscher was a small Merle breed, which might have had also Dane type harlequin, but it went fully extinct about 70 years ago. Catahoula Leopard Dog from Louisiana, USA has its origins in herding and hunting dogs European immigrants brought. So, there you are. A rather short list of breeds. There are also some breeds with Merle, which have been created only during the last 50 years or so, and which are created more by crossing existing breeds than from a real landrace population. Such breeds (like Alapaha Blue Blood Bulldog) can have Merle traditionally, but the breeds itself are not "traditional breeds" due to their short history.
Which breeds have gotten Merle later officially?
This is still a shorter list, as there is mainly just one breed: Hungarian herding breed Mudi. When breed books of Mudi were originally closed, no Merle dogs were in the breed and so there was no Merle. But later the stud book was opened, and Mudi type working landrace dogs could be presented to a breed council and accepted, if they filled certain requirements. One Merle dog was officially accepted during 1990's, and after that Merle was offcially in the breed. Merle is called "cifra" in this breed. There might be Merle also in Bearded Collie nowadays and for the same reason, aka working landrace dogs can be registered as Beardies if a breed council accepts, and some Merle working dogs have been suggested to be registered. Also, in Chihuahuas, Merle might have been introduced via small European dogs before the stud book was fully closed.
But there is Merle in other breeds too! Where did it come from?
Yes, sure. But as the Merle mutation really happened only once in the history of the domestic dog, and if Merle was not in the breed gene pool when stud book of that breed was closed, and no new Merle individuals were introduced to the breed officially, Merle has happened due to a non listed breed cross and the pedigree of the dogs in question have been falsified.
In some cases this might have happened accidentally, and Merle might have hidden a generation or few in e/e yellow dogs (like it might have happened in American Cockers), but still, Merle came from another breed via crossing and didn't just "happen". Nowadays, with good parentage DNA tests, every breeder, who suddenly gets Merle pups in a pure breed which hasn't traditionally had Merles ever, could easily test the parentage and find out where that new color pattern came from. Some of the "new Merle breeds" might have had Merle already for 40-50 years (like American Cocker Spaniel and Poodle) and so before proper parentage or Merle testing, but in majority of these breeds Merle seems to have appeared only during the last 20 years, and without any real explanation how it happened.
But there are breed tests, sure I can prove my dog is purebred even when it is merle? There really are breed tests and some are quite good (especially with common breeds), but they can't show true parentage for longer than a few generations. These tests check certain DNA strands, and when such strands come from parents, they are still rather long. When they come from grandparents, they are on average much shorter, and when they come from further than 3rd generation, they have turned into such short fragments that no test can tell from which breed they really come from. All breeds are still domestic dogs, all dogs share mainly the same DNA and as all breeds still have at least some variation, even a good test can't tell that "yes, this merle Poodle has for sure one Aussie in 7th generation"!