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Eurwentala — Wild Horses 3
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#ancient #cavepainting #colour #dna #genetics #horse #iceage #pleistocene #wildhorse #equine
Published: 2018-11-03 10:32:39 +0000 UTC; Views: 32973; Favourites: 1028; Downloads: 0
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Description
This is a chart on colours of Eurasian wild horses or tarpans (Equus ferus) of Late Pleistocene and Holocene - a surprisingly varied population, as shown by ancient dna and cave art. This is the stock from which our domestic horses were bred from. They only went extinct around year 1900.
After publishing the first two versions of this one, I kept reading about colouration in wild and domestic equids, had some interesting discussions here on dA, and felt the need to make an updated version.
This piece is also available as a high-quality print in our new Society6 shop: society6.com/product/eurasian-…
Depicted is a selection of possible combinations of the alleles known to have been present in wild tarpans. According to the data set of Pruvost et al. (2011), the most common colours were bay dun, grullo, and spotted bay dun. All these seem to be also depicted in European cave art. According to Imsland et al. (2016) the dun allele was also polymorphic in wild horse population, causing some individuals to be darker than others.
Different combinations would have necessarily occurred from time to time, when horses of different colours mated. The LP allele, producing leopard spotting, is affected by a large number of modifiers. I depicted a few possible outcomes of it, but for the time being, we have little hints on which patterns where really present. The spotted horse paintings of Pech Merle cave, France, look like they have a leopard or blanket spotting with dark head and neck.
Additions to the earlier versions include subtler details not revealed by ancient dna testing so far. All horses now have pangaré colouration, that is, countershading on the body typical to wild equids and breeds considered "primitive". The level of pangaré varies, as shown by wonderful cave paintings in Ekain Cave, Spain. Some horses only had whitish bellies, while in others, the white reached up their sides and down their legs. This might have been variety between summer and winter coats, and/or adaptations to environments with different amounts of tree cover. These horses had a variable amount of striping on their legs and necks, from nonexistent to quite strong, which was also documented in detail by someone in Ekain Cave 13 000 years ago. Another detail often shown in cave paintings is that the neck and head are darker than the rest of the body.
Ancient dna studies are the other important source of information. The letters underneath each horse refer to their alleles. These four were polymorphic in the tarpan population:
Agouti locus
A - dominant allele causing brown coat
a/a - recessive allele causing black coat
Extension locus
E - dominant allele enabling black in coat and mane
e/e - recessive allele preventing black coat and mane (result being a chestnut horse)
Dun locus
D - dun, a diluting factor present in wild horses and asses. Causes lighter coat colour and primitive markings (two-coloured mane, stripes etc.)
d1/d1 - recessive allele causing non-dun colour (black, bay, or chestnut, depending on the base colour). Leaves some primitive markings visible.
(d2 is the non-dun allele dominant in domestic horses, but unknown in wild ones)
Leopard / varnish roan locus
lp/lp - no leopard complex, no spots
LP/lp - leopard complex, spotted
LP/LP - leopard complex, mostly white. There is a night vision defect associated with homozygous animals, probably making them vulnerable to predators.
I had to assume this one, since genetic test for it was only developed in 2016 and it hasn't yet been widely tested on ancient horses:
PATN1 - patterning factor, causes leopard spots with LP
References:
www.pnas.org/content/108/46/18…
www.nature.com/articles/ng.347…
science.sciencemag.org/content…
onlinelibrary.wiley.com/doi/fu…
Cave paintings:
Lascaux bay dun horse: www.ancient.eu/img/r/p/500x600…
Lascaux horse paintings with stripes, spots, dark heads, and possibly non-dun colouration: donsmaps.com/lascaux.html
Ekain Cave grullo, bay dun and striped horses: www.agefotostock.com/age/en/St…
Spotted horses of Pech Merle: en.wikipedia.org/wiki/Pech_Mer…
Chauvet blackish horses: en.wikipedia.org/wiki/Chauvet_…
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Comments: 38
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Fantastic work! I felt a little odd about the first chart, but this one is great.
That’s grullo leopard spotted horse is probably my favorite one on this chart, other depictions of leopard-spotted wild horse (all like, 2 others that exist unfortunately) just look too unnatural and domestic. Do you think it occurred like black leopards/jaguars, appearing in habitats in which it could function and staying recessive where it isn’t advantageous? Causing night blindness and being pretty obvious in most situations makes me feel it would be limited to some degree, not a “usual” morph.
Also I noticed you depicted both full-bay horses with a dark mouth, I thought they would have had a light mouth like bay dun horses. Is there something I missed or..? I just be on the same page.
Overall really good, we need more wild horse references for people, and I’ll have my own up hopefully soon too.
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Thanks! It's been a learning curve, finding the connection between horse genetics and their appearance as wild animals. 
I'm not completely sure about the dark mouth areas of the bay horses, but that's what the domestic ones usually seem to have in photos. Some bay dun horses also have a dark mouth, while those of primitive breeds (such as Norwegian fjord horses and Przewalski's horses) often have a small amount of dark pigment around the mouth and nostrils and a light area around it. I'm not sure if the light mouth area is connected to having the dun allele, or if it's a separate wild horse thing.
About leopard spotting - your idea of a rare, occasional colour is certainly plausible. It just makes me wonder that Pruvost et al. found as much as six leopard spotted horses in a sample size of 31. That's a huge amount for a rare type - but on the other hand, there are apparently also areas where black leopards are more common than spotted ones!
Another idea I've been entertaining is that the leopard spotting gene was accompanied by a collection of modifier alleles, making the colouration far more fine-tuned to the animal's ecology and less variable than in domestic horses today. Much like wild mammals can have white markings, but they are not blotched all over the place, but fine-tuned by natural selection.
A spotted horse is obvious and would seem to be vulnerable to predators, but then again, zebras exist too.
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Not exactly. Zebras look like that because it makes them basically invisible (and thus less vulnerable) to tsetse fly + all these stripes look like a confusion made motion.
Leopard complex could have arisen from something similar. Also being mostly white in the north has its benefits.
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Wonderful work! I presented it on my blog, I hope that is ok: breedingback.blogspot.com/2018…
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Thanks for sharing! I have often read your blog articles. Very interesting!
And thanks for the constructive criticism, too! The knowledge that black suppresses pangaré is new to me - I'll look into it and update accordingly. About chestnut, I'm aware it's only known from one dna specimen from the Holocene, but since it was a supposedly wild horse, I considered it worth adding to the chart. Even if chestnut was derived from introgression with domestic horses, it was nevertheless part of the colour variation of the very last wild horses. Much like black wolves are a thing even though the black allele comes from dogs.
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Thank you for doing this, it will be so useful when picturing ancient horses!
My fav horses would have to be the bay dun with the darker body (almost looks like a light bay with primitive markings and extreme Pangaré) and the grullo with the stripes on it's back. But I love all these reconstructions - lots of pretty ponies!
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Thanks! I'm especially fond of the grullo with stripes and extreme pangaré. I practically directly copied the coloration from a painting in Ekain Cave.
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This looks amazing 😍 I’d have to say my favorites are the bay dun blanket and grullo leopard!
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Thanks! I'm personally most fond of the grullo with stripes and extreme pangaré.
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I'm not sure whether the scientific community is all that interested in the colors of ancient horses compared to other traits. Is there really a way to know for sure? It's a little like speculating what color dinosaurs were, which hasn't drawn that much attention as compared to the skin vs feathers controversy. If we want to reference Pleistocene cave paintings for horses, then how accurate can that be? I mean they were ARTISTS after all, how can we know that they painted realistically.
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As Spottedchest replied before me, there's a lot more to go on with Ice Age horses than with dinosaurs: not only dna, but also frozen carcasses with intact fur. It touches interesting research questions regarding, for example, the ability of animals to adapt to rapidly changing climates (which is kind of relevant at the moment), and the natural level of variety in megafaunal populations before the time of human-caused bottlenecks (which we don't really have anymore).
I don't know how interested exactly the scientific community is in these questions, as I haven't done any gallups, but I find them interesting at least.
While the Ice Age painters sure were artists and sometimes depicted things that don't exist - such as half-man half-animal hybrids - they were generally remarkably realistic in their animal portrayals. It helps that many of the depicted animals are still alive: reindeer and European bison are very popular subjects, for example. We don't see imaginary colour patterns or extra antlers in them - they are often so naturalistic, you could basically use them as a field guide. This is why people tend to trust the paintings quite a bit regarding the appearances of extinct animals, too. Of course, the paintings should not be blindly trusted and there's a danger of misidentifications - which is why it's good to pair them with genetic studies (such as the one about leopard spotting) or comparisons with living wild equids (as with stripes and pangaré colour).
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Well, unlike dinosaurs, we can use DNA tests for colours found in modern horses on actual DNA samples from the ancient horses, so there's a lot less guesswork involved. Plus, it is very interesting from a standpoint of understanding when coat colours in horses started appearing. The only modern wild horses we have were descended from a very small population and so have a very restricted range of colours, and if this research had not been done we would not have realised how ancient some colours are. Like leopard spotting - who would have guessed it was so ancient, without the genetic evidence?
Plus it raises questions about coat colour in relation to the horses adapting to different environments. So I'd have to say for researchers involved in studying these horses it would probably be quite interesting.
On referencing cave art, it's a bit hit and miss, but at least with the horses we know that there were horses that carried the Leopard spotting gene around at the same time the cave-art was painted, so it's not too crazy to assume that they were painting them based off of horses they have seen, rather than just making things up. Of course, it doesn't tell us how common these horses were; humans have a tendency to pay more attention to the unusual
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Also the so-called caballoid or caballid or caballine group phylogeny or taxonomy is quite messy: this complex of populations are known variously as Equus caballus (domestic horses and their feral derivatives), E. ferus (tarpans or forest horses) and E. przewalksii (Przewalski’s horses or takhis). Ancient populations of this complex have been given a few other names, including E. lambei and E. lunensis.
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Yeah, sure is. There are a lot of names for horses that either probably or possibly were part of the same complex: graziosii, valeriani, antunesi, algericus, scotti, occidentalis, and others too. Some of these could well have been different enough to warrant their own species, though there's no definite evidence so far. We'll just have to wait for more evidence and new taxonomic revisions.
However, we do know that the tarpan, the domestic horse, and the Przewalski's horse are all closely related and definitely should not have separate species names. In newer taxonomies, they are most often all treated as subspecies of E. ferus. They all were once part of the Eurasian steppe-and-forest wild horse population. And that's the one this artwork depicts - the evidence comes from an area stretching from Spain to Siberia.
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Yeah that's true, recently it has been even suggested that the Przewalski's horse might be a feral variety of the domesticated horse.
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Now that was a fascinating study! In fact, it was suggested that the Przewalski's horse is descended from an independent domestication of Eurasian wild horses, that happened in Kazakhstan some 5500 years ago. The living domestic horses were domesticated somewhere else, perhaps later. I just linked the study to another comment in this discussion.
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So there are zero truly wild Equus ferus anywhere....
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Indeed. There's a Finnish song with the lyrics "are there still wild horses?". I often wonder if the writer is still alive and if he or she knows that the answer is no.
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Here: science.sciencemag.org/content…
And here's a popular article if you can't access the original: www.sciencemag.org/news/2018/0…
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Beautiful composition!
However it must be noted that the spotted coat of the ‘Dappled horses of Pech-Merle’ is a bit dubious. It is true that Pruvost et al. (2011) found genetic data indicating that some Palaeolithic horses were ‘leopard spotted’ just like some modern domestic breeds, most famously the Appaloosa, and that they therefore argued that those ancient dappled horse images were representing a genuine anatomical feature (the idea that some Pleistocene horses really were so boldly patterned is pretty incredible, but then so is the presence of striping on zebras), however such a colour scheme is unknown in wild living horses so it’s often been assumed that the spotting is some sort of artistic decision. Further support for this view comes from the fact that other animal illustrations in the same cave are also shown with a spotted coat: we see evidence that Palaeolithic artists were sometimes putting random spotting on all sorts of things (even on otherwise blank bits of cave wall) and were not necessarily intending those spots to represent zoological accuracy. Furthermore, even if the genes associated with a spotted coat have been discovered in fossil horse DNA, it doesn’t necessarily follow that there’s a direct link between those genes and what’s seen in some cave art.
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Thank you for your comment!
I agree that the spotted horses of Pech Merle alone are not definite proof of leopard spot patterning in wild horses, as it could surely be artistic license or have some symbolic meaning. However, combined with the ancient dna evidence, the case starts to look much more convincing. That's two separate lines of evidence.
The absence of spotting in modern wild horses means little: they are a relict population descended from just 9 surviving zoo animals, with almost no genetic diversity left. In addition, they are not truly wild, but a feral population descended from domestic Botai horses 5500 years ago. And within the ancestral Botai horse population, leopard spotting WAS present. We actually know they have lost their leopard allele during the last few thousand years of population decline. science.sciencemag.org/content…
As for bold patterning, as you said, zebras exist, and they're far more striking than a dun-leopard spotted horse. Quite a few other living animals have spots or bold white-and-dark contrasts - say, fallow deer, leopards, cheetahs, pandas, weasels, many antelopes... In addition, as I said in the description, we don't know that kind of modifying alleles these horses had to accompany their leopard alleles. In wild animals, patternings are often much more finely tuned than in domestic ones, since humans select for variability. There could well have been a very specific way the spotting would develop and function as disruptive patterning.
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Yeah the idea of boldly patterned Pleistocene horses is not especially outlandish, however I wouldn't regard the cave paintongs at the Cave of Pech-Merle de Cabrerets, France "a line of evidence" because I'm not convinced that these are really meant to be depictions of horses that really were leopard-spotted in life: note that spots like those present on the horses have been depicted elsewhere on the cave walls.
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That's all up to interpretation, really. The painters did not exactly leave labels.
However, in European Ice Age cave art, animals are most often depicted quite naturalistically. The Pech Merle horses have realistic details such as dark heads and the way the spots follow the body shape of the horse. For these reasons, I'd lean towards actual spotted horses instead of horses that just happen to have spots painted on top of them. On the other hand, I think the mammoth here (www.pechmerle.com/grotte-ornee… ) simply has spots painted over it for some other reason - the spots don't follow the outline or shape of the animal and don't make sense in light of what we know about mammoths.
Either way, it doesn't matter much. To the best of our knowledge, leopard spotting complex was present in Eurasian wild horses, and whatever the people who painted Pech Merle were thinking is not as interesting to me as that fact.
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