An extinct canid hiding in plain sight in the domestic dog?
Everyone knows that a certain black-and-tan pattern occurs again and again - either on an individual basis or as the colouration typical of the breed - in otherwise diverse breeds of the domestic dog (Canis familiaris).
These range in body size from the chihuahua (https://www.askideas.com/55-very-beautiful-chihuahua-dog-photos-and-pictures/) to the rottweiler (https://www.petbarn.com.au/petspot/app/uploads/2015/01/23.-Rottweiler.jpg) and beyond...
...and in body shape from the daschund (https://www.playbarkrun.com/dachshund-colors/ and https://www.freepik.com/premium-photo/black-tan-dachshund-walking-nature_10166528.htm and https://www.rover.com/blog/breeds/dachshund/ and https://www.dachshund-owner-guide.com/dachshund-colors.html#gallery[pageGallery]/1/) to the afghan hound (https://www.alamy.com/stock-photo-a-profile-view-of-a-healthy-beautiful-grizzle-black-and-tan-afghan-146356983.html).
However, what is poorly appreciated is that the black-and-tan (or in some cases 'chocolate-and-cream' or 'chocolate-and-tan') pattern is one of the most significant and unexplained aspects of the domestic dog.
This pattern is bilaterally symmetrical and forms an integral and coherent system of markings connecting the head, chest, legs and hindquarters (https://doggiedesigner.com/black-and-tan-dog-breeds/).
The system includes vestigial/incipient forms of adaptive features typical in wild mammals, such as a frontal flag (https://www.dreamstime.com/black-tan-mixed-large-breed-puppy-standing-full-length-photo-black-tan-color-mixed-large-breed-puppy-dog-standing-image114250081 and https://www.inaturalist.org/observations/89243136) and an ischial flag (https://www.shutterstock.com/image-photo/black-tan-rottweiler-puppy-standing-on-1635788887 and https://www.inaturalist.org/observations/92095076).
(Please note that the pattern https://www.facebook.com/806111259438680/photos/black-and-tan-german-shepherds-the-black-tan-german-shepherd-dogs-can-be-rich-bl/807666499283156/ in breeds such as the German shepherd - although often confusingly called black-and-tan - is different, and irrelevant in this context.)
So, what is particularly significant about the black-and-tan pattern in the domestic dog?
Well, could it be that here we have a virtually complete representation of the colouration of an extinct and unnamed wild species of Canis, which contributed to the ancestry of this, the oldest of all domestic species?
Most naturalists believe that the wolf (Canis lupus) is the main or sole ancestor of the domestic dog (e.g. see https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0125759 and https://en.wikipedia.org/wiki/Origin_of_the_domestic_dog).
And this seems a safe assumption in the case of at least a few breeds such as the saarloos wolfhound (https://www.zooplus.co.uk/magazine/dog/dog-breeds/saarloos-wolfhound), which lack the black-and-tan pattern in any individual (https://www.petguide.com/breeds/dog/saarloos-wolfhound/).
However, the trouble is that the black-and-tan colouration is unknown in either the wolf or any other of the living wild species of Canis.
For the black-and-tan pattern to have appeared in descendants of solely the wolf, this entire system of features would have had to arise as a single mutation. Furthermore, the pattern would have had to be strongly preferred by humans during subsequent selective breeding.
These conditions seem implausible for several reasons.
Firstly, the black-and-tan pattern is 'wild-type' in its regular configuration (e.g. see https://thehappypuppysite.com/rottweiler-temperament/), quite unlike the haphazard mutational features typical of many species of domestic mammals and birds.
Secondly, the black-and-tan pattern is recurrent and persistent among breeds regardless of extreme modification of body size and proportions. This conservatism indicates a deep ancestral feature, not one bred into the dog by domestication.
Thirdly, the black-and-tan pattern shows the same kind of subtle individual variation as do wild-type colourations in mammals in general.
The extent of the pale features varies considerably among individuals. The ischial patch, in particular, is slightly different in every individual (albeit always symmetrical). Furthermore, there is black vs tan, dark brown vs fawn, brown vs cream, etc.
Fourthly, the black-and-tan pattern remains in the populations of 'primitive' or 'retrogressive' relatives of the domestic dog, particularly the dingo.
Fifthly, where any irregular and asymmetrical marking occurs in combination with the black-and-tan pattern, the former is superimposed on the latter, not the other way round (https://hdwallpapers.cat/wallpaper/smooth-collie-katie-herding-breed-black-tan-6Bu2.jpg). A white patch on the chest is common, but this applies also to white on the face and feet.
And sixthly, the black-and-tan pattern has some aesthetic appeal to many persons, but not more so than various other, more typically domestic, patterns, such as the patchwork of tones seen in the border collie (http://www.vetstreet.com/dogs/border-collie#1_izc4ixoo and https://www.deviantart.com/kimptone/art/NEW-Border-Collie-Colour-Chart-117559446).
What all of this suggests is that the black-and-tan pattern is derived not from the wolf but from a different, extinct ancestor. This was possibly a jackal-like species living in Eurasia in the Pleistocene, that left few recognisable bones.
Please bear in mind that the domestication of Canis familiaris may have begun as long ago as 30,000 years.
Let us look with fresh eyes, then, at working breeds such as the kelpie, which have retained/regained medium body size and a generalised body shape (https://www.101dogbreeds.com/wp-content/uploads/2014/12/Black-and-Tan-Australian-Kelpie.jpg and https://www.cleverkelpies.com/tracker-cosmo and http://jembellafarm.blogspot.com/2016/06/casterton-kelpie-muster.html and http://gibbinshatleykelpie.blogspot.com/2009/03/australian-kelpie.html) similar to those of most wild species of Canis.
Is it not plausible that the overall appearance of the kelpie resembles this extinct species?
The likeness I am suggesting is, of course, phenotypic rather than genotypic. Nobody should doubt the complexity of selective breeding, over tens of thousands of years, that separates the kelpie from any extinct ancestor or co-ancestor. And hybridisation with the wolf remains likely as part of this process.
However, what I suspect is that - by accident rather than by design - the overall phenotypic trajectory may have circled back to the appearance of an extinct species separate from the wolf.
And - if we dare to hypothesise boldly enough to create a new search-image for this extinct species in the fossil record and in genetic analyses - could we even apply a working name of 'Canis rubronegrus'?
In the dingo, the black-and-tan pattern occurs as part of colour-polymorphism. Even if only some individuals of the ancestral, jackal-like species had this colouration, this would not militate against my hypothesis. This is because there is no colour-polymorphism in the wolf.
Another rationale could be based on the remarkably different natures of wolf and domestic dog. Many naturalists may be unaware of how different the two species are, psychologically, and how inimical the wolf truly is to human interests (https://www.youtube.com/watch?v=TBFGlCipnqo). More than is the case in large felids and even the spotted hyena (Crocuta crocuta), it is in the niche of the wolf to treat humans as potential prey.
In the light of the extremely predatory, untrustworthy nature of the wolf to humans, plus the incongruity of the wild-type colouration of the domestic dog with that of the wolf, I suggest that it is somewhat far-fetched to invoke that the latter has been largely domesticated from the former.
Further illustrations:
https://www.adoptapet.com/pet/20937390-barrie-ontario-irish-wolfhound-mix
https://www.inaturalist.org/observations/87511931
Saint Bernard
https://unsplash.com/photos/YRUzuSC48Zs
Tibetan mastiff
https://www.purina.com.au/dogs/breeds/tibetan-mastiff#.YUie0ivitDM
Coonhound
https://thehappypuppysite.com/black-and-tan-coonhound/ and https://www.hotdogpetphotography.com/dogs/dog-day-black-tan-coonhound/ and http://www.vetstreet.com/dogs/black-and-tan-coonhound
Comentarios
https://en.wikipedia.org/wiki/Pleistocene_wolf
http://www.doggenetics.co.uk/tan.html
https://www.biorxiv.org/content/10.1101/2021.10.10.463851v3 and https://www.newscientist.com/article/2294090-extinct-japanese-wolf-is-the-closest-wild-relative-of-dogs-yet-found/
@milewski
Have you seen this article?
Link: https://www.nature.com/articles/s41586-022-04824-9
From the article:
"Here we analysed 72 ancient wolf genomes spanning the last 100,000 years from Europe, Siberia and North America. We found that wolf populations were highly connected throughout the Late Pleistocene, with levels of differentiation an order of magnitude lower than they are today. This population connectivity allowed us to detect natural selection across the time series, including rapid fixation of mutations in the gene IFT88 40,000–30,000 years ago. We show that dogs are overall more closely related to ancient wolves from eastern Eurasia than to those from western Eurasia, suggesting a domestication process in the east. However, we also found that dogs in the Near East and Africa derive up to half of their ancestry from a distinct population related to modern southwest Eurasian wolves, reflecting either an independent domestication process or admixture from local wolves. None of the analysed ancient wolf genomes is a direct match for either of these dog ancestries, meaning that the exact progenitor populations remain to be located."
@paradoxornithidae
Many thanks for showing me this paper, which I have not previously seen. It does seem to be inching towards a more realistic view of the ancestry of the domestic dog.
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