The European Wild Horse
This is a guest article, kindly contributed by Daniel Foidl, an Austrian law student and Palaeo-enthusiast. Daniel is the creator of the long-running Breeding-back Blog a site dedicated to exploring the process of restoring extinct fauna via selective breeding of their domesticated descendants. Additionally he is an amateur palaeo-artist, you can check out his work at Deviantart.
The horse is one of man’s most important domestic animals. Just like cattle, horses descended from a once widespread wildtype that is now extinct because of human influence. The western subspecies of the wild horse, Equus ferus ferus, had a range from the Iberian peninsular to the western Eurasian steppe, where the horse was most likely domesticated. Although the domestic horse is well-known to us, the wild form is kind of elusive – it is not certain when it died out, how common it was, what it looked like, and there is not even a consensus on how to name this animal. Also, there is and has been a lot of confusion regarding the European wild horse, local types, its extinction as well as horse breeds associated with it. Some common anecdotes revolving the subject have to be considered myths and fabrications without a scientific basis (1).
“Tarpan”, a problematic term
The European or western wild horse is often referred to as “tarpan”. Yet, the European wild horse was never colloquially called “tarpan”. This name is of Turkic origin, and was a local term for free-roaming horses in the Russian steppe that came up in the literature in the 18th and 19th century. It is not clear what kind of horses this name actually referred to – whether these were true Equus ferus ferus, Przewalski’s horses, feral domestic horses or hybrids cannot be ascertained anymore (1,2). Some contemporaneous authors considered the free-roaming horses of the Russian steppes escaped domestic horses, also because of their inhomogeneous appearance (3,4). To add to the confusion, from the middle of the 19th century onwards, authors started to use the term “tarpan” as a synonym for the European or western wild horse (4). Some authors also preferred to differentiate between a “forest tarpan” and a “steppe tarpan”, based on material whose assignation to wild horses is dubious and methods that are nowadays considered inadequate (1). Thus, Equus ferus gmelini, Equus sylvestris and Equus ferus sylvaticus are junior synonyms of Equus ferus ferus. Because of these confusions and the unclear situation concerning what the animals historically called tarpans actually were, it is better not to use the term as a synonym for European wild horses or Equus ferus ferus (2).
Range, population genetics and ecology of the European wild horse
During the Pleistocene, horses were common and widespread across Eurasia (5). Wild horses are a frequent motif in ancient cave art, such as in Lascaux and Chauvet. According to genetic research, Pleistocene horses were subdivided in an isolated Iberian population and one large population from the Pyrenees to Siberia (6). Interestingly, a 2019 study has shown that Iberian wild horses were more basal than Siberian wild horses (labelled as Equus lenensis), while the Przewalski’s horse Equus ferus przewalskii and the domestic horse result as sister clades (7). That indicates that the Przewalski’s horse, which, according to recent research separated from the domestic horse between 38-72 kyr BP (8), is closer related to the domestic horse than native Iberian wild horses (7). Since a 36.000 year old horse specimen from Belgium was found to be genetically closer to Iberian wild horses and domestic horses, it is likely that the wild horses portrayed in cave art are not Przewalski’s horses but the predecessors of Holocene European wild horses (7).
During the Holocene, horses got increasingly rare in Europe (1,5,9). This decline in number is likely due to an increased forestation of the continent. Many open lands turned into forests, what was problematic for the horse as an open land animal (9). The wild horse disappeared from Britain (10) and nearly vanished from Central Europe (9). It was not until when humans created open lands with their agriculture that horse remains increased again (9), but it has to be noted that after the arrival of domestic horses wild horse remains are very difficult to distinguish from their domestic counterparts on a morphological basis. Because of that, it is not known when the European wild horse disappeared altogether. Free-roaming horses have been mentioned in several historic sources, but if they truly describe wild horses will be discussed down below. As the nature of these horses described is dubious, the exact extinction date for the western wild horse Equus ferus ferus is unknown.
What is also unknown is where the range of Equus ferus ferus ended and that of the Eastern subspecies, the Przewalski’s horse, began. The question is how far westwards the original range of Equus ferus przewalskii extended. The range of both subspecies might have been continuous as introgression from E. f. przewalskii was found in a European wild horse (11).
The European wild horse was most likely also an open land-dwelling grazer as its living relatives, the domestic horse and the Przewalski’s horse. Also, it is highly likely that it was a herd animal like other horses (10).
Life appearance of the European wild horse
As long as there are no skeletons described that undoubtedly belong to European wild horses, their morphology and body size is up to speculation. The coat colour phenotypes of Equus ferus ferus, however, have been resolved as there have been studies testing ancient horse material for coat color alleles.
Based on the alleles found in ancient horse samples, it seems that five colour phenotypes have been present in the European wild horse populations during the late Pleistocene: bay, bay dun, black, black dun, and leopard spotted (12, 13, 14). During the Holocene, black alleles increased in frequency and became the predominant colour alleles, while bay alleles dominated the Pleistocene samples (13). It is speculated that the black allele provided a selective advantage in an increasingly forested Europe during the Holocene (13). Whether the phenotype was black or black dun is an open question. So far, the authors have been unable to amplify the dun factor in the samples examined (13), what might indicate that late Holocene European wild horses were predominantly black.
An important but unclear aspect is the mane of European wild horses: whether it was falling or erect. No carcasses of Holocene wild horses have been found in Europe which could clear up this question, and historic accounts are neither precise enough nor is it certain that the free-roaming horses described were true wild horses.
The fact that an E. lambei carcass from North America allegedly has a long mane is sometimes used as an argument for falling manes in European wild horses. However, E. lambei is less closely related to the domestic horse than other forms with erect manes like the Przewalski’s horse or E. lenensis (a carcass belonging to this form has a short mane of only 15 cm [15]). The horses portrayed in Pleistocene cave art apparently all had erect manes. Despite the large resemblance with Przewalski’s horses, according to genetic research those horses are more likely the ancestors of Holocene European wild horses than Przewalski’s horses (7). Therefore, it is not unlikely that European wild horses had an erect mane, as all other wild equines living today.
Putting the evidence together, many Holocene European wild horses might have looked like this (the colours black dun, bay and bay dun would be possible as well, especially for early Holocene European wild horses):
Fig. 1: Life reconstruction of the European wild horse based on coat colour genetics and the assumption of an erect mane. © Daniel Foidl
Domestication of the horse
According to the most recent research, it is unknown when and where the modern domestic horse was domesticated (7). The domestication of the horse must have been very sex-biased as domestic horses have a very limited Y chromosome diversity (16) but have a great mitochondrial diversity (6, 17). This indicates that few wild stallions but many mares were involved in the history of domestic horses. As the mitochondrial DNA is very diverse, it is likely that local introgression from wild mares of different wild populations contributed to the modern domestic horse (6, 17). Thus it is possible that, although the horse most likely was not domesticated on continental Europe, European wild horses contributed to the modern domestic horse.
Historic records of free-roaming horses in Europe and the Eurasian steppe
There are historic records of free-roaming horses in Europe and the western Eurasian steppe, and one individual was also photographed, but it cannot be ascertained if those horses were genuine wild horses, feral horses or hybrids.
Many of those historic sources report horses that probably were dun-coloured, since a dark dorsal stripe and leg stripes are often described (4). Several reports mention a mouse-like colour or greyish colour with a dorsal stripe, what most likely describes a black dun colour. As outlined above, black dun is one of the possible colours of European wild horses according to genetic research. Regarding the mane, the historic sources are not very precise. Often the mane is described as short, frizzy or rugged (3,4), what probably indicates a short falling mane and not an upright mane. Some reports, such as one from the 16th century, say that these free-roaming horses got tame after some time in captivity (4), or that stallions could be trained (18). One famous report was that of Samuel Gottlieb Gmelin from 1768, who described free-roaming horses in Voronezh, Russia. According to him, those horses had a short frizzy mane and were typically mouse-coloured, sometimes also white or grey. Peter Pallas reported free-roaming horses from the East of Russia. Most of them had a greyish brown colour or white legs, but greys as much as brown and black horses were found as well. Pallas considered those horses to be feral horses that descended from escaped military horses (4). A very extensive description of free-roaming horses is provided by Charles Hamilton Smith in 1841. He reported mountain-forest ponies in western Europe with heavy manes and long bushy tails, but also described those horses locally called “tarpan” very precisely. They varied in colour from tan, Isabella or mouse-coloured and had a whitish winter coat. Smith writes that the general appearance of the tarpan resembled “vicious mules”. His illustration of the tarpan from 1853 shows a brown horse with a short frizzy mane.
So it seems that the majority of those free-roaming horses were of a black dun colour. Black dun is one of the colours that are confirmed for European wild horses. The fact that domestic colour variants such as white or grey or with white legs were also reported suggests at least admixture. The fact that some of the contemporaneous authors considered them feral horses also is a hint that these horses were not genuine wild horses. And if European wild horses indeed had a short erect mane, all of horses described with frizzy or long manes can safely be considered feral horses or at least hybrids.
Fig. 2: The only horse considered a tarpan that was photographed, the Cherson Tarpan.
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A number of individual free-roaming horses have been described as well. These are known as the Cherson tarpan, the Krim tarpan and the Dubrowka tarpan. The Cherson tarpan is the only individual considered a tarpan that was photographed. It nearly has no features attributed to wild horses and a thick long mane (10), and thus might well have been a feral horse. The Krim tarpan was suspected to be a feral horse already back in its lifetime (4). The Dubrowka tarpan was the last animal considered to be a tarpan and died in 1918. It was 140-145 cm tall, had a mouse-coloured coat and a semi-erect mane (19). It might have been a feral horse or hybrid because of its comparably large size. The last free-roaming horse of the Russian steppe was shot in 1879 (4). As it is unknown how far westwards the original range of the Przewalski’s horse reached, it is possible that many of the individuals considered tarpans were actually Przewalski’s horses or hybrids between domestic horses and this animal (2).
All in all it seems likely that those free-roaming horses of Europe and the western Eurasian steppe described in former centuries were feral horses, or at least hybrids with feral horses and not original Equus ferus ferus. Thus, it is unknown when the wildtype of the domestic horse actually died out. It is possible that it disappeared during the antiquity or even earlier, and got replaced by feral horses that descended from escaped individuals later on. Another possibility is that escaped domestic horses simply swept the gene pool of the already rare wild horse until its original form vanished. What can be said with certainty though is that the disappearance of Equus ferus ferus was, as in the case of the aurochs, due to human influence. The wild horse apparently was not a very common animal during the Holocene, and hunting as well as habitat limitation lead to the end of the European wild horse.
The European wild horse and the Konik
A popular story that is sometimes even repeated in scientific papers is that the Polish Konik pony breed is allegedly the descendant of the last population of Polish wild horses. According to this story, the last wild horses of the Zamoyski zoo were sold to farmers of the Bilgoraj region and became included into their stock in 1806 (4). In the 1920s, agriculturist Tadeusz Vetulani allegedly collected the most wild horse-like ponies from this region and used selective breeding for wildtype traits to create the Konik breed. This is the common story of the Konik being a “tarpan” descendant. There are several problems with this story, however.
First of all, it is by no means given that the horses kept at the Zamoyski zoo were wild horses (for the discussion of historic free-roaming horse populations, see above). Furthermore, the only source claiming that these horses were sold to farmers at the begin of the 19th century is written by Julius Brincken in 1826. His work is problematic as it includes a lot of errors and fabrications (1). That those horses, even if they were wild horses (for which there is no clear evidence for), were donated to local farmers is unlikely for a number of reasons (1), as well as that much of the influence of these horses was tolerated in the highly bred farm horses, or that after more than hundred years when Vetulani started to investigate the rural horses of this region much of them was left in the domestic stock. Therefore, even if the horses at the Zamoyski zoo were wild horses (for which there is no evidence for), and if they were indeed donated to local farmers, it is highly unlikely that the rural horses of the Bilgoraj region of the 20th century were greatly influenced by them (1).
Also, it is not true that the Konik is the result of a selective breeding project by Vetulani. In fact, the Konik is a landrace that existed already before Vetulani started to investigate Polish rural horses. It was called “Panje horse” back then (4). Vetulani’s experiment was not a selective breeding approach but rather he thought that keeping a number of those horses in a natural area would lead to a re-development of wildtype characters. Vetulani’s experiment ended in the 1950s and his herd was only one of many Konik/Panje horse studs during that time (4). Vetulani did not create the Konik, he merely coined the modern name of the landrace that replaced Panje horse (4).
What is also important to note is that Koniks were by no means uniform back then. It displayed a wider range of colours than today and some of those colours still may occasionally appear in the modern Konik (4).
Lastly and perhaps most importantly, if the Konik was indeed a descendant of the last European wild horses, it would have to be genetically different from other domestic breeds. However, this is not the case as the Konik clusters with other domestic breeds in mitochondrial DNA analyses (6, 17).
The Konik is not the only horse breed that is claimed to be a descendant of European wild horses. The same is said of the Exmoor pony from England and the Portuguese Sorraia horse. The Exmoor pony cannot be a descendant of British wild horses, as these died out early in the Holocene before domestic horses arrived on the isle (10). Genetically it is closely related to other Northern pony breeds and does not have any unique haplotypes what would be expected if it recently descended from wild horses (6, 16).
The Sorraia horse was created from farm horses collected by agriculturist Ruy d’Andrade and is claimed to be a descendant of the Iberian wild horse by its advocates. As Iberian wild horses were less closely related to domestic horses than Przewalski’s horses, the Sorraia would have to be genetically set apart from other domestic horses if it indeed descended from Iberian wild horses. This is not the case, however, as the Sorraia was found not to be a predomestic horse or related to Iberian wild horses (20).
Citations
1. Van Vuure: On the origin of the Polish konik and its relation to dutch nature management. 2014.
2. Castelli: Don’t call me Tarpan. 2013.
3. Charles Hamilton Smith, 1841: The Natural History of horses, with Memoir of Gesner
4. Tadeusz Jezierski, Zbigniew Jaworski: Das Polnische Konik. 2008.
5. Leonardi et al.: Late Quaternary horses in Eurasia in the face of climate and vegetation change. 2018.
6. Cieslak et al.: Origin and history of mitochondrial DNA linages in domestic horses. 2011.
7. Fages et al.: Tracking five millennia of horse management with extensive ancient genome time series. 2019.
8. Orlando et al.: Recalibrating Equus evolution using the genome sequence of an early Middle Pleistocene horse. 2013.
9. Sommer et al..: Holocene survival of the wild horse in Europe – a matter of open landscape? 2010.
10. Bunzel-Drüke, Finck, Kämmer, Luick, Reisinger, Riecken, Riedl, Scharf & Zimball: „Wilde Weiden: Praxisleitfaden für Ganzjahresbeweidung in Naturschutz und Landschaftsentwicklung“. 2011
11. Wutke et al.: Decline of genetic diversity in ancient domestic stallions in Europe. 2018.
12. Pruvost et al.: Genotypes of predomestic horses match phenotypes painted in paleolithic works of cave art. 2011
13. Sandoval-Castellanos et al. 2017: Coat colour adaption of post-glacial horses to increasing forest vegetation. 2017.
14. Imsland et al.: Regulatory mutations in TBX3disrupt asymmetric hair pigmentation that underlies Dun camouflage colour in horses. 2015.
15. Lazarev, P.: Large mammals of the Anthropogene of Yakutia. 2005.
16. Lindgren et al.: Limited number of patrilines in horse domestication. 2004.
17. Jansen et al.: Mitochondrial DNA and the origins of the domestic horse. 2002.
18. Gabriel Rzaczynski: Historia naturalis curiosa regni Poloniae. 1721
19. Hardy Oelke: Wild horses then and now. Kierdorf-Verlag.
20. Lira et al.: Ancient DNA reveals traces of Iberian Neolithic and Bronze Age lineages in modern Iberian horses. 2010.