Two zebus with traits of the Indian aurochs

At first glance, zebus seem to be rather different from the aurochs. But there are certain traits found in many zebus that are very reminiscent of the wildtype. For example, many zebu landraces from South Asia have a very short trunk with long legs (more so than most taurine breeds on this world) and small udders. Many also have a comparably long snout. Surely, their often hanging ears, the fleshy hump (which is less likely to be a wildtype trait than a trait that appeared after domestication) and the often rather derived horn shapes give them an unusual appearance that creates the impression they are more removed from the aurochs than taurine breeds, but the huge udders, the piebald colour and tiny horns of Holstein-Frisian, for example, are not wildtype traits either. And not to forget, zebus have been found to share alleles with the European aurochs that taurine cattle have lost [1]. It is most parsimonious to assume that these alleles were also present in the Indian aurochs. Thus, zebus are actually more "primitive" than their looks suggest at first glance. 

While searching for zebus with wildtype traits I found photos of one living zebu and one skull that both respectively share traits with Bos primigenius namadicus. 

For the living individual, go here and here. It has a crazily extreme primigenius spiral. And as so often when a domestic cattle individual has a perfect primigenius spiral, it is a steer (the picture description on shutterstock says it is an ox, thus castrated). Nevertheless, the horns are interesting. Not only because of their curvature, but also because they are antero-posteriorly compressed on the proximal half and thus oval in cross section, which was a trait of B. p. namadicus. In the African aurochs, B. p. mauretanicus, and also some European aurochs, B. p. primigenius (particularly those from the Pleistocene), we see the opposite, namely dorsoventrally compressed horns at the base. Thus, the horns of this zebu steer resemble the Indian aurochs in this respect, thus they can be considered "primitive". I would love to see the bony horn cores of this individual, to see if they have keels. A bony keel on the dorsal and ventral ridge of the horn core was a trait of Indian aurochs, particularly in early individuals [2], that later was lost in zebus again. Whether or not these keels were visible in the living animals is unknown, as no keratinous horn sheaths of this subspecies have been preserved. Therefore it would be interesting to see the bony horn cores of that steer. 

The zebu skull that is interesting can be seen here and here. What makes the skull interesting is that it can be seen that the forehead is slightly convex, which is a trait inherited from B. p. namadicus and the opposite of what is seen in the other aurochs subspecies and taurine cattle (a planar or slightly concave forehead). Also, the profile of the snout is completely straight, while European aurochs and taurine cattle have a slightly convex bulge at the base of the snout. The profile of the zebu skull, and that of many other zebus, thus resembles that of wild B. p. namadicus in these two respects: 

The skull of the Indian aurochs in profile view is at the bottom right; a cross section of the horn with the keels can be seen at fig. 6

Too bad that there is no complete skeleton of the Indian aurochs available. Plentiful of remains of B. p. namadicus have been found, but always only fragmentary specimen consisting of few elements and never a complete skeleton. My suggestion would be to create a composite skeleton in order to get a more complete picture of the morphology of this aurochs subspecies by taking well-preserved remains of individuals of the same sex and size and create a (more or less) complete skeleton. The same has been done for the neanderthal, from which no complete skeleton is known either.  

Literature 

[1] Orlando et al.: The first aurochs genome reveals the breeding history of British and European cattle. 2015. 

[2] Bökönyi: Zebus and Indian wild cattle. 1997.  

Bos primigenius trochoceros?

The species of the aurochs, Bos primigenius, has many synonyms – last time I counted it was 8, counting only those that are based on wildtype material and there might be more (with those based on cattle there would be much more). One of those synonyms is Bos trochoceros, a species which was described for Pleistocene European aurochs. However, as the differences between Pleistocene European aurochs and Holocene European aurochs is not dramatic enough to justify a split on species level, it has been synonymized decades ago. But what about subspecies level? Might it be justified to classify Pleistocene European aurochs as Bos primigenius trochoceros? 

There were differences in the morphology of Pleistocene and Holocene European aurochs. First of all, the former reached very large sizes of 200 cm withers height or more, while individuals from the Middle and Late Holocene were smaller (what was most likely due to anthropogenic factors). It also had – on average – considerably larger and more wide-ranging horns as the horn size of Holocene aurochs was decreasing and also the curvature was narrower (with large-horned Holocene individuals such as the Sassenberg bull being exceptions) throughout this period. The coat colour, however, was seemingly identical between Pleistocene and Holocene European aurochs, as a comparison between cave paintings and historic texts suggest. The question if the differences in body size and horn size are enough for a split on subspecies level is not easy to answer, as taxonomy is rather subjective – what is distinct enough for one worker is not distinct enough for the other. 

A Pleistocene aurochs skull from Germany with massive and wide-ranging horns - Bos primigenius trochoceros?

However, genetic information might endorse a split on subspecies level. Southern European aurochs (at least Italian ones) have the mitochondrial haplotype T which is also found in taurine cattle (hence the “T”), while those from the Northern half of Europe have the haplotype P (from “primigenius”). Southern Europe was a refuge for the aurochs during the last glacial, when the mammoth steppe covered most of its former range in Europe. The different haplotype of northern aurochs suggest that Europe was recolonized from the East rather than from the South after the last glacial [1]. So, there is a genetic difference between Southern and Northern European aurochs, and it must be noted that during the Pleistocene the range was restricted to Southern Europe. 

As it happens, Bos trochoceros is based on a Pleistocene skull from Siena, Italy [2]. And Bos primigenius is based on a Holocene skeleton from Haßleben in Germany, thus the northern half of Europe. Doesn’t that fit nicely? So, can we say that Bos primigenius primigenius represents only the Central and Northern European aurochs from the Holocene, that migrated from the East to Europe after the last glacial and have the P haplotpye, and that Bos primigenius trochocerosrepresents the Southern European aurochs that were slightly larger, had larger and more wide-ranging horns, were present in Europe during the last glacial and all had the T haplotype? I don’t consider this assumption all too absurd. We also have to consider that there likely was a continuum between both forms, as their range was continuous during the Holocene (similar as in the case of Canis lupus lupus and Canis lupus italicus). Not all Holocene aurochs with the P haplotype had smaller horns (see the Sassenberg specimen) and not all of them were smaller than Pleistocene Southern European ones (see the Prejlerup specimen which might have been around 195 cm tall in life). 

It seems that I am not the only one who considers the use of the trinominal name Bos primigenius trochoceros legitimate. The name has been used in a 2020 paper and a 1995 work for Middle Pleistocene aurochs remains in France [3,4].

If a split on subspecies level within the European aurochs was legitimate, this also would have consequences for the evolution of cattle. Since Southern European aurochs have the T haplotype, Near Eastern aurochs in the fertile crescent from 10.000 years ago that were the ancestors of taurine cattle, likely had the same haplotype. Quite possibly, the populations were connected at some point, and most likely the aurochs entered Southern Europe via Anatolia. Therefore, it is likely that Near Eastern aurochs from that time can be or must be considered Bos primigenius trochoceros too. That means taurine cattle were not domesticated from the nominate subspecies, Bos primigenius primigenius. Nevertheless, B. p. primigenius in this strict sense left a lot of living descendants because of secondary introgression into cattle in Europe (go here). 

 

I consider this split on subspecies level at least possible – I am very open for the possibility that trochoceros rises from the grave of the junior synonyms thanks to genetic and morphological information. We would have five mainland subspecies of the aurochs in this case: the Northern European aurochs Bos primigenius primigenius, the Southern European (and possibly Near Eastern) aurochs Bos primigenius trochoceros, the North African aurochs Bos primigenius mauretanicus, the Indian aurochs Bos primigenius namadicus, and the East-Asian aurochs Bos primigenius suxianensis. I am also convinced that this would not be over-splitting as other bovines with a large geographical range such as the cape buffalo which is divided into two to three subspecies (depending on the status of Syncerus nanus), and this includes only those that live today in the late Holocene. The aurochs simply was a species with a large geographical range over a comparably long period of time, which goes hand in hand with the evolution of several subtypes. 

 

Literature

 

[1] Mona et al.: Population dynamic of the extinct European aurochs: genetic evidence from a north-south differentiation pattern and no evidence of post-glacial expansion. 2010. 

[2] Rütimeyer: Überreste von Büffeln (Bubalus) aus den quaternären Ablagerungen von Europa. 1870.  

[3] Uzunidis: Dental wear analyses of Middle Pleistocene site of Lunel-Viel (Herault, France): did Equus and Bos live in a wetland? 2020. 

[4] Tuffreau et al.: Le gisement acheuleen de cagny-l’epinette (somme). 1995. 

Genome editing for "breeding-back" the aurochs

Traditional “breeding-back” takes a long time until satisfying results are achieved, also because cattle are a comparably slow-reproducing species. Also, “breeding-back” cannot revive the aurochs for several reasons, it can merely produce an imitation of the wildtype. That is why many dream of using genome-editing in modern “breeding-back” projects. Genome editing using the CRISPR-Cas9 method enables to cut and modify the genome of an organism, and to insert or exchange alleles in the genome. The now-dead Uruz Project (which now only exists on Wikipedia) started with the claim that they want to use genome editing for “breeding-back” in order to speed up the process. It sounded great, but there are some obstacles. 

First of all, only a handful of genes responsible for the phenotypic characters of interest in cattle have been resolved. For example, we know that a brindle coat colour is caused by a dominant allele on the Agouti locus, that the polled condition is caused by a dominant allele on the Polled locus, and the three alleles on the Extension locus and aggression in cattle is probably influenced by the MAOA locus (go here). But we have no clue which alleles are responsible for horn size or curvature, the various colour dilutions we see in Podolian cattle and Chianina (which are used in “breeding-back”), the size of the hump, the sexual dichromatism and many other traits. And some traits, such as body size, proportions and other morphological traits (which make up the most important differences between cattle and aurochs) are likely controlled by hundreds of genes or even more (cattle have 22.000 genes). Therefore, a lot of research would have to be done in order to use genome editing efficiently for “breeding-back” an imitation of the aurochs. 

Genetic linkage is kind of an argument pro and contra genome editing in “breeding-back” at the same time. It is possible that some morphological/optical aurochs-like traits are linked to wildtype traits with other functions (for example immunological, developmental, physiological). If the wildtype allele(s) for a certain morphological trait is inserted into another genome with genome editing instead of being introduced with traditional breeding, the wildtype allele for non-visible characteristics would not be transferred to the new genome. This is a scenario where genome editing would not be beneficial for the goal (to have as much wildtype alleles as possible) and where traditional breeding would be more effective. However, the opposite scenario would be equally as likely, that some wildtype alleles are genetically linked with domestic alleles on the same chromosome. If the wildtype allele and the domestic allele lie close together on the chromosome, it is not only impossible to get rid of the domestic allele without also losing the wildtype allele but it is also very unlikely that the linkage is ended by recombination. In this case, genome editing would be beneficial: the domestic allele could be cut out and replaced with a wildtype allele from the same locus from another cattle breed that still has the wildtype allele. This is the scenario where genome editing would be highly beneficial for “breeding-back”, and I believe this is what the Uruz Project was referring to when they said they want to use this technique. However, as outlined above, as long as the alleles responsible for the phenotypic traits of relevance, it is not possible to use genome editing for “breeding-back” effectively. 

This is where the fully resolved aurochs genome that was resolved in 2015 from a British Neolithic aurochs bull comes into play. So far, no particular gene has been identified that played a considerable role in the domestication of the aurochs. In horses, two such genes have been identified: one influencing the ability of the animals to bear weight on their back, and one influencing fear response and docility (here). If the same work was done for the aurochs, one could take these genes in the genome of modern cattle (preferably cattle that are already aurochs-like, not Holstein-Frisian) and replace their domestic alleles on these important loci and replace them with alleles taken from the aurochs individual. It has also been found that zebus have some wildtype alleles that were replaced by domestic alleles in domestic cattle (here). These could also be replaced by aurochs alleles in an aurochs-like cattle individual. This modification of the genotype of an already aurochs-like taurine cattle individual would be a reintroduction of organismic wildtype traits that could be very beneficial for the cattle’s survival in nature under natural selection (be it immunological, developmental, physiological, genomic by the removal of deleterious domestic alleles, morphological or behavioural). 

I think it might be possible (though more effortful) to go one step further: replacing all the domestic allele of an aurochs-like taurine cattle individual with those of the aurochs. The result would basically be a recreated aurochs. It would not be a recreation of the original genetic diversity of the wildtype, but at least one individual. As an aurochs enthusiast, I would of course love this scenario. But if that is not possible for technical reasons, even the reintroduction of single wildtype alleles that are lost in modern cattle would already be a success. I really hope that someone one day is going to try it (what would require the “the aurochs can be bred back anyway” mentality to finally disappear). 

The Vig bull and its horns

The Vig bull is one of the two almost complete aurochs skeletons from Zealand, Denmark. It's from the early Holocene and shows several injuries to the bone caused by arrows. The skeleton is likely a male because of its size, robust postcranial skeleton and long skull shape. However, compared to other finds from males like the London skull, the eye sockets are not nearly as prominent and the overall build of the skull not very robust. 

The horns are not as strongly curved as those of many other aurochs bulls, and also the angle between horns and snout is larger than average (about 80°). On Wikimedia Commons there is a nice photo of the skeleton in frontal view (here). I could not resist to track the skull out with a pencil and do a life reconstruction of the head and horns: 

Perhaps I made the snout look too feminine for a bull, but the skull is very slender. There is no general rule how much keratine to add to the length and thickness to the horn cores because apparently there was much individual variation in the aurochs. 

Video of a great Lidia bull

Repeatedly I wrote on my blog that I consider the Spanish fighting bull (Lidia) the most aurochs-like or least-derived taurine cattle breed that is left on this world. In the youtube video linked down below there is yet another example for a very aurochs-like Lidia bull. 

The bull appears at 0:22. Look at its horns, its morphology, its skull shape. Simply wonderful. All in all it is a very aurochs-like individual. The colour is not wildtype colour (which would be an E+//E+ genotype), but colour is an easy fix as it is controlled by only a few genes. The morphology, however, is controlled by most likely a very large number of genes and thus a bull that has the right morphology but not the right colour is much more useful for "breeding-back" than a bull with the right colour but not the right morphology. And considering that most "breeding-back" cattle so far have a morphology that is not quite there yet, this Lidia bull would help to boost their aurochs-likeness considerably.

However, this breed has to be used wisely due to its problematic behaviour. What I would do if I had the chance would be to create a herd of about 30 Chianina cows and let them be covered by this Lidia bull. The results will be F1 Lidia x Chianina that have both a full set of Lidia chromosomes and Chianina chromosomes. Then I would pick one of the F1 bulls (either the best-looking or least aggressive one), and let them cover all of the F1 cows. The resulting (roughly) 15 F2 will display a wide phenotypic variation spectrum. Some individuals might have the Lidia size and Chianina horns (not desired), or Chianina size and the horns of the Lidia P individual. It requires luck to get an individual with horns and morphology like the Lidia bull, Chianina size and Chianina leg length and an E+ phenotype without visible dilution factors et cetera. I would pick the best bull of the F2, also taking the behaviour into account for pragmatic reasons, and let him cover all of the F2 cows. Maybe the F3 individuals will be pretty good already and also more or less homozygous for the desired traits due to the consequent line breeding. If not, one could repeat the process endlessly (that way, highly inbreed and genetically homozygous laboratory mice lines have been produced that are used for genetic research. The so-called purging of deleterious alleles produces genetically homogeneous lines that do not suffer from an inbreeding depression), but I would expect that the F3 would be pretty good already. It would maybe lack horn volume for an average aurochs, but it would likely be within the variation of the European aurochs (compare with, for example, the Prejlerup bull). The genetic diversity would be narrow, but my goal would not be a large, genetically diverse population but rather a couple of high-quality, genetically comparably homogeneous individuals that are suitable for improving the aurochs-likeness of other herds. Bulls from such a line could be used as sires on other "breeding-back" herds. That way the potential of this Lidia bull would be used for the breeding of aurochs-like cattle. 

Unfortunately this is all a phantasy scenario of mine, but it is always great to see that there are such great Lidia bulls around. 

Bos primigenius or Bos taurus?

There is some confusion about which name is the proper scientific name for the aurochs, Bos primigenius or Bos taurus. In this post, I am going to investigate the question which of those names is the legitimate scientific name for the aurochs. 

If one considers domestic cattle and aurochs different species because the former has been domesticated, the case is clear which scientific names they should have: the aurochs would be Bos primigenius, described by Bojanus in 1827, and domestic taurine cattle would be Bos taurus, described by Linnaeus in 1758. But there is no scientific consensus on whether domestic animals and their wildtypes should be regarded as one species or separate species. I tend to not regard domestic animals as taxa that need a proper scientific name at all (go here for my post on that). 

So, if aurochs and domestic cattle would be one species, with the aurochs being the wildtype and domestic cattle man-made modified versions of the aurochs created by artificial selection, what is the proper scientific name for that species? This is now where it becomes tricky. 

Due to the rule of priority of the ICZN, the first name used to describe a species has priority. In this case, Bos taurus would be the proper scientific name of the species containing aurochs and domestic cattle because it is the earlier name. However, in 2003 the ICZN decided that 17 names of wildtypes that are pre-dated by names for domestic forms should be conserved, including Bos primigenius (opinion 2027). However, to complicate the issue, Linnaeus actually referred to the aurochs in his description of Bos taurus from 1758. He mentioned the aurochs as “ferus urus” (= “wild aurochs”) living in Poland. Apparently, he was not aware of the fact that the aurochs probably already had died out when he described the species (go here for the youngest aurochs remains currently known). This is taxonomically not relevant however, Linnaeus definitely described the aurochs and domestic cattle as one species in 1758. 

Referring to the aurochs as Bos taurus is therefore definitely legitimate. However, I prefer to follow opinion 2027, also because Bos primigenius at least has a holotype (the Haßleben specimen), while Bos taurus does not. Therefore, it is up to ones’ preference whether to use Bos primigenius or Bos taurus for the species that contains the aurochs, and also depending on your opinion on the taxonomic status of domestic animals in general.

 

The horns of the African aurochs and its evolutionary implications

I did a post on the African aurochs, Bos primigenius mauretanicus, a few years ago. The African aurochs is said to be morphologically very similar if not identical to the European aurochs, so that van Vuure (2005) concludes it might be exclusively geographical [1]. The only difference to the European aurochs mentioned in my old article is the fact that bulls likely had a colour saddle. However, there might be morphological differences in the horns of the African aurochs, which have previously not been recognized in the literature. 

 

In 2015, the oldest aurochs skull found so far was described [2]. It is from Tunisia and is very large-horned. But what was interesting to me about the horns was not their size, but their shape and orientation relative to the skull. They have an angle of 40° relative to the snout, which is narrower than in the European aurochs, where the range of angles of the horns relative to the snout is between 50 and 80° on average, and larger in single exceptions (such as in the skull exhibited at Horsholm). Also, the horns seem to be dorsoventrally compressed at the base or proximal half, while the distal end of the horn seems to be round in cross section. 

Due to the age of the skull (700.000 years), I was unsure whether to classify it as a member of B. p. mauretanicus, or maybe as a basal aurochs that lived before subspecies differentiation. 

However, I recently found a depiction of another African aurochs skull, that, because of its geologically younger age, certainly is a member of B. p. mauretanicus. The anatomical drawing is from a work from 1931 and is labelled as Bos opisthonomus, which is a junior synonym of B. p. mauretanicus. It shows the same anatomy as the 700.000 years old skull from Tunisia: horns facing forwards in a narrow angle (35°) and dorsoventrally compressed at the base or proximal half. The image is from Duerst (1931) [3]. 

An anatomical drawing of an African aurochs skull, from Duerst 1931

Thus, it seems that these two traits (dorsoventrally compressed horns at the base, horns facing forwards in an angle sharper than in the European aurochs), were general anatomical traits of the African aurochs. That the horns of the African aurochs faced forwards in a sharp angle also fits historic descriptions, because Herodotos describes that in North Africa there were bovines with horns so long and forwards-facing that they had to graze backwards [1]. Likely this referred to the African aurochs. Also ancient depictions of African aurochs show horns growing parallel to the snout, what suggests that the horns were facing forwards in a narrow angle. In European aurochs, and sometimes also domestic cattle, the horns were/are oval in cross section at the base as well (in Pleistocene European aurochs more so than in Holocene ones) [1], but this trait is definitely more expressed in the African aurochs. 

 

Apparently, the aurochs varied in horn orientation from subspecies to subspecies. While the African aurochs had the narrowest angle, the Indian aurochs and possibly B. p. suxianensis had the largest angle, and the European aurochs was in between. Whether the difference in horn orientation has a functional purpose or if the variation was merely a result of genetic drift is unclear to me. 

 

It is interesting to speculate about the evolutionary implications of the horn anatomy of B. p. mauretanicus. There are two conflicting hypotheses on the origin of Bos and the aurochs. One of the hypotheses postulates that Bos and the aurochs in particular evolved in Africa from Pelorovis oldowayensis, the other one suggests that Bos originated from Leptobos in Asia, and the aurochs from the very large-horned Bos acutifrons in India. The fact that the horns of the Indian aurochs are more upright than those of the other aurochs subspecies seems to support the latter hypothesis, as the horns of Leptobos are rather upright. However, the fact that the horns of the African aurochs have such a narrow angle between horns and snout and the dorsoventrally compressed horn bases support the origin from Pelorovis oldowayensis, as this species has horns with a very narrow angle relative to the snout and dorsoventrally compressed horns. Other cranial traits seem to support an origin from Leptobos, on the other hand. The origin of Bos probably can only be resolved by finding more fossils of relevant taxa. 

 

Literature

 

[1] van Vuure: Retracing the aurochs – history, morphology and ecology of an extinct wild ox. 2005. 

[2] Martinez-Navarro et al.: The early middle Pleistocene archaeopaleontological site of Wadi Sarrat (Tunisia) and the earliest record of Bos primigenius. 2014. 

[3] Duerst: Grundlagen der Rinderzucht – eine Darstellung der wichtigsten für die Entwicklung der Leistungen und der Körperformen des Rindes ursächlichen, physiologisch-anatomischen, zoologisch-paläontologischen, entwicklungsmechanischen und kulturhistorischen Tatsachen und Lehre. 1931. 

 

 

Differences between the Quagga Project zebras and the quagga

The Quagga Project likes to call their zebras “Rau quagga”, after the founder of the project Reinhold Rau. That is why I made the post Please don’t call it quagga. The advocates of the name “Rau quagga” state that it is O.K. to call the zebras that way because the “Rau” in “Rau quagga” underlines that they are different animals from the quagga. I, however, think it is not legitimate to call something that is not a quagga a “quagga”, with or without the “Rau” in front of it. Calling those zebras “Rau zebra” would be more adequate if the zebras of the Quagga Project need a name, because they are zebras in any case. 

 

Names aside, I made a post on the differences between the quagga and other zebras not so long ago. I think it is time to have a look at the differences between the zebras of the Quagga Project and the quagga. 

The Quagga Project focuses only on the pelage colour characteristics. The coat colour of the Quagga was variable to a certain degree. I tried to capture this diversity in a drawing, using the preserved quagga skins as a reference: 

 

The quagga was variable in the extent of the striping, but there are some general differences between the quagga and the zebras of the Quagga Project. 

The striping is supposed to link the zebras of the QP with the quagga, and indeed the amount of reduction of the striping that has been achieved is impressive, but there are some clear differences in the stripe pattern of the quagga and the zebras of the QP. 

1) In many of the zebras of the QP the stripes on the neck alternate between broad, solid black stripes and faint, narrow stripes. This was not the case in the quagga. All quagga skins show that the quagga had exclusively broad, solid black stripes on the neck. 

2) The stripes on the face of the zebras of the QP are very narrow, producing a broad white space between them. In the case of the quagga, the stripes on the face are rather broad, with only a narrow quite area in between them. 

The second clear difference in coat colour between the zebras of the QP and the quagga is the base colour, i.e., the colour between the stripes on the trunk. In the quagga the base colour of the trunk was brown, sometimes more intense sometimes less intense, but always brown. The base colour of the trunk on the zebras of the QP has some brownish shade but is not nearly intense as in the quagga specimen documented. The QP is aware of that and hopes they will achieve that brown base colour in the future. 

Another possible difference is the length of the mane. I have the suspicion that the quagga had a shorter mane than other plains zebras, based on the photographs and the preserved skins. The zebras of the QP have rather long manes compared to the documented specimen of quagga. This is only my suspicion; it would have to be verified by measuring the manes of the preserved quagga skins. 

 

Another very important difference between the quagga and the zebras of the quagga project is the fact that the quagga does not share any mitochondrial haplotypes with the living plains zebra subspecies (see my article linked above). There is no reason to assume the case is any different in the zebras of the QP, so therefore the animals are also genetically different. 

 

The quagga and the zebras of the QP are superficially similar because an amount of stripe reduction on leg and trunk has been achieved in the latter, but that is it. There is no justification for calling the zebras of the QP quagga or “Rau quagga”, they are simply plains zebras with a reduced stripe pattern. General differences, such as in the striping on the anterior part of the body or the lack of a brown base colour on the trunk will remain. The project hopes to achieve the brown base colour one day, but I wonder if this is possible without new mutations enabling an increased production of pigment on the trunk area.

 

I am writing this not in order to criticize the QP, not at all. I just think that we should always stay objective and should not declare the revival of an extinct animal that is still dead as a dodo based on superficial similarity. I am happy that there is the QP, because their zebras could be very useful for outbreeding with quaggas if one individual or a few individuals could be genetically resurrected using genome editing one day. 

A possible skull of Bos primigenius siciliae

A while ago I did a post on the aurochs and insular dwarfism. On Sicily, the Sicilian dwarf aurochs, Bos primigenius siciliae, was found during the late Pleistocene. Now I found a photo of a possible skull of that subspecies on Wikimedia Commons: 

Uploaded by the user Ghedo on Wikimedia Commons

I am not sure if it is really a skull of B. p. siciliae or just an aurochs found in Sicily, but the skull does not look very large. If it is really a skull of the Sicilian dwarf subspecies, it could mean that it was a comparably long-horned subspecies. Too bad the facial skull is not preserved, it would be interesting to know if this subspecies exhibited paedomorphy, which is often found in dwarf species. 

Another study debunks the Konik myth

Unfortunately, many still believe in the Konik myth. According to the narrative, the Konik allegedly descends from the last wild horses of Poland kept at the game park of Zamosc that were allegedly donated to local farmers who bred them into their domestic horse stock. This story is very unlikely and goes back to only one sentence in a historic source of very dubious accuracy. Closely tied to the Konik myth is the usage of the word "tarpan" for the European or western Eurasian wild horse. Many authors uncritically adopted speculations from other authors and portrayed them as facts in their own works, and so the myth became very persistent. The narrative became: "The tarpan was the European wild horse, and the Konik is the descendant of the tarpan".

The recent paper of Lovasz, Fages and Amrhein from last year examines the history of the word "tarpan" in scientific literature, and also the history and origin of the Konik myth. The study can be found here. 

The idea that the Konik descends from Polands last wild horses goes back to a notion by Julius Brincken in his 1826 work. He mentions in one sentence that those last wild horses were donated to local farmers of the Bilgoraj region and bred to domestic horses of that region. The Konik, so claim later authors in the 20th century, is said to descend from these hybrids. However, it is by no means certain that those horses at the game park of Zamosc were wild horses. Most likely they were hybrids (see here). Also, Brincken's work is not credible as it includes many inaccuracies and fabrications (see van Vuure, 2014). Even if Brincken's notion is correct, it is unlikely that the farmers tolerated a great influence of wild horses in their highly bred farm horses. And even if they did, the subsequent story of those hybrids is not documented. It is not known if those horse lineages, if they would have existed, continued into the 20th century when hippologists became interested in the rural horses of that region which were called Panje horses (the name Konik was coined later, in the 1920s and 1930s) and it is also not documented that the Konik itself descends from those purported lineages. Yes, it is true that the Konik has the same coat colour as the late European wild horse (black dun, also called grullo or mouse dun). But that is the result of artificial selection. The original stock of the Konik in the 1920s included many colours, black dun was only one of them. It was subsequent selective breeding in the middle and later half of the 20th century that created the now mostly black dun Konik (see Jeziersky & Jaworski 2008). 

Thus, the Konik myth is a romantic story but not based on solid evidence. It is merely based on one sentence in a very questionable historic source and even if this sentence is accurate, there are many other variables in the equation (did the farmers tolerate wild influence in their highly bred horses? Did those lineages continue into the 20th century? Does the Konik really descend from those lineages, if they existed at all?). Some want the Konik to be a wild horse, but this pony is rather a black dun robust landrace (nothing more and nothing less), not a recent wild horse descendant. That does not diminish its value in landscape conservation, but I wish a wider variety of horse breeds would be used for that purpose. 

I wonder why still so many believe in the Konik myth. Horse breeding seems to be somewhat romanticized and connected to emotions, the Sorraia origin story or the Exmoor pony story for example are not based on reliable facts either. 

Literature 

Lovasz, Fages & Amrhein: Konik, Tarpan, European wild horse: An origin story with conservation implications. 2021. 

van Vuure: On the origin of the Polish konik and its relation to Dutch nature management. 2014. 

Jeziersky & Jaworski: Der polnische Konik. 2008. 

The last aurochs were from Bulgaria, 18th century (!)

The year 1627 is commonly provided as the extinction date of the aurochs, when the last cow of the Jaktorow population died in Poland. A horn core from Moldavia which dates back to the early 17th century suggests that there was another remnant population in that country at least [1]. In 2020, however, a horn core was found in Sofia which probably dates back to the first half of the 18th century [2]. This is the youngest aurochs material known today and very exciting. It means that the extinction date of 1627 is wrong, and that the less accessible forests of Bulgaria or perhaps the entire northern Balkans provided enough space for a remnant aurochs population that was able to survive until the first half of the 18th century. 

Here is a link to the paper. 

Literature 

[1] Bejenaru et al.: Holocene subfossil records of the auroch (Bos primigenius) in Romania. 2013. 

[2] Boev, Z.: The last Bos primigenius survived in Bulgaria (Cetartiodactyla: Bovidae). 2022. 

How the Heck brothers could have done their work better

In a post from 2015, I evaluated the “breeding-back” experiments executed by Heinz and Lutz Heck. I came to the conclusion that they made several technical mistakes and could have done their work better given the circumstances of their time. This post is going to look at how they could have done their experiments better using the possibilities they had when they started in the 1920s. 

 

Step 1: Getting an accurate picture of the aurochs 

 

One of the reasons why the Heck brothers failed at creating a phenotypic copy of the aurochs is that they did not have an accurate, precise picture of the aurochs. They did research, and they also resolved at least some coat colour traits of the animal, but the picture of the aurochs they had included errors and needless speculations such as a red dorsal stripe instead of a grey one as the historic evidence suggest, or a greyish tone in the colour of the cows. The biggest problem was that they failed to recognize the morphology of the aurochs. Apparently, they never saw a mounted aurochs specimen or if they saw one, they did not take a close look at it. Doing so would have told them that the trunk of the aurochs was much shorter than in domestic cattle, that the legs were longer, the head larger and more elongated, and that aurochs had a hump formed by long spinal processes in the shoulder region. Surely, it was not as easy to see a mounted aurochs skeleton as it is today (a quick google search is enough to find photos nowadays), but there were more or less complete aurochs skeletons back this time in Germany (at least the Haßleben specimen which was described in 1827). They did not study the skeletal remains of aurochs, thus the most important part of the aurochs’ life appearance, the morphology, played no role in the projects of the Heck brothers. 

They could have done better by looking for a museum that would have had a mounted aurochs specimen and study its differences to modern cattle. Their research on the colour of the aurochs should not have included baseless speculations, but rather they should have strictly followed what the historic evidence that was available to them inferred. Doing that would have enabled them to get a pretty accurate picture of the European aurochs’ morphology and life appearance even back in the 1920s. 

 

Step 2: Creating a strict breeding goal and not ignoring certain traits 

 

Before starting any breeding, it would have been vital to set up breeding criteria that are based on what has been found out about the aurochs’ life appearance. The Heck brothers did not have a clear breeding goal because they did not have a precise picture of the aurochs. Furthermore, they ignored certain traits. Body size was ignored, udder size was ignored, the morphology was not recognized. Thus, anything that roughly met the Heck brothers’ idea of the coat colour of the aurochs and had longer horns would have matched their rather wide selection criteria. Therefore, it is not surprising that they announced success after a few years of breeding, since their breeding goal was not clearly defined. If the Heck brothers had created a clear catalogue of traits the cattle should have that also included all the traits found in the aurochs and not only some, their breeding would have been much more efficient. 

 

Step 3: Finding suitable breeds

 

This step was without doubt the trickiest of all, because back this time there was much less information available. It was unknown where the aurochs was domesticated, were the most aurochs-like breeds would be found and there were barely any breeding associations to contact and no internet. The brothers, however, did find out that many Iberian breeds show traits of the aurochs. Lutz Heck was particularly impressed by the Spanish fighting bull, which is indeed one of the most aurochs-like breeds that are still around. Heinz Heck, on the other hand, did not use the Spanish fighting bull but included a number of derived breeds, because he hoped that they carry invisible aurochs traits that would surface again when crossed with more primitive breeds. This hope, however, did not fulfil. Retrospectively, it was a mistake to include derived breeds such as Black-pied lowland cattle, Murnau-Werdenfelser and others. The set of breeds selected by the Heck brothers was thus not ideal. The fact that they ignored certain traits (body size, udder size) or did not recognize them (morphology), was another reason why their set of breeds was not ideal. Thus, if the Heck brothers would have known about the morphology of the aurochs and cared about size, they would have looked for breeds that add these traits. If they would have stumbled across Chianina while searching for large breeds, they would have found a breed that adds large size and long legs and to a certain degree small udders. Lutz Heck recognized that Watussi can have aurochs-like horns but did not use that breed. Using it would have considerably increased the size of the horns of their cattle and would have compensated the small horns of other breeds used. Thus, if the Heck brothers would have used a different set of breeds, the result would have been much more aurochs-like. Corsican, Camargue and Lidia are breeds that were used (Lidia only by Lutz Heck), they were valuable because they contributed the right colour (Corsican) or had an athletic morphology (Camargue and Lidia). If they sticked with those three breeds, and maybe also Podolian cattle (for the cold resistance and winter coat), but would not have used the derived ones, and included Watussi and Chianina, the potential for an aurochs-like outcome would have been much larger than it was with the set of breeds they chose. A mix of Corsican, Camargue, Lidia, Chianina, Watussi and perhaps a Podolian breed would have had great potential. 

 

Step 4: Strict selective breeding focusing on the breeding goal 

 

As the Heck brothers did not have a very precise breeding goal, they barely carried out strict selection, leading to a very heterogeneous result. More precise selection criteria and strict selective breeding would have created a more aurochs-like outcome. 

 

Step 5: Setting up a studbook and ensuring that selective breeding is maintained while the breed is expanded to other locations 

 

It was certainly sloppy that the Heck brothers did not set up a studbook for their cattle. Also, the fact that there was no official catalogue containing selection criteria that they themselves and other breeders should have followed created chaos when the population was expanded to other locations. Some breeders selected their cattle for an aurochs-like appearance, such as the Wildgehege Neandertal, others did not, and Heck cattle became a very heterogeneous breed. Creating a catalogue with selection criteria that are based on the aurochs could have prevented this at least to a certain degree.  

 

If the Heck brothers did those five steps, and if the breeders that came after them sticked to the selection criteria, the resulting cattle would not only be better than Heck cattle as they are now, they would even be a lot better. I would even say, we could have the cattle of our dreams now if the Heck brothers would have done their work more thoroughly. Almost 100 years of efficient selective breeding is enough to create a homogeneous but genetically diverse breed of cattle with the right colour, large or even very large size, the right morphology and horns and a sufficient winter coat. Modern “breeding-back” projects are on a good way, but it will take its time until the goal is accomplished. If the Heck brothers did their work more thoroughly, that goal possibly might have been reached now in 2022. 

The skull of a Lidia bull

We have no living specimen of aurochs to study and compare with aurochs-like cattle, and we tend to compare the living animal in flesh with the skeletal material of the aurochs - this is comparing apples to bananas and is prone to errors. That is why I think it is very interesting to compare what is comparable, namely bones to bones. Months ago I found a photo of a mounted skeleton of a Heck bull (go here). Recently I found a photo that is equally interesting, a photo of a Lidia bull skull (go here). Here is a photo of the skull on display the Naturkundemuseum Berlin for comparsion: 

How does the skull of this Spanish fighting bull compare to that of an aurochs? What is striking is that the snout seems to be as long as in the aurochs relative to the distance between the eye sockets, what means that this individual had a snout as long as in the aurochs in life. The postorbital portion, however, is definitely shorter as in the aurochs (I know the perspective is not ideal, but I have seen many aurochs skulls from that perspective and the postorbital region is always longer). This could maybe go hand in hand with the reduced brain volume of domestic cattle and paedomorphy. The eye sockets are not as pronounced and massive as in the aurochs, but I am not sure if that difference would be visible in the living animal. Also, not all aurochs bulls had eye sockets as prominent as in the Berlin skull, f.e. the skull of the Vig skeleton has less prominent eye sockets. The horns of the Lidia skull unfortunately have their sheaths still on, but I think it is obvious that the horns of the Lidia bull are smaller than in the aurochs, less curved and point forwards in a sharper angle as in the aurochs. 

All in all I would say that a Lidia skull is similar to that of the aurochs, but there are differences, most notably in the postorbital region and the horns. 

Does the "Augsburg aurochs" really show an aurochs?

The “Augsburg aurochs” made by Charles Hamilton Smith in 1826 is one of the most famous depictions of an aurochs. It is based on an oil painting which dates to the 16^th century and that was purchased by Smith in Augsburg, Germany. The oil painting, which might have been based on a live aurochs, is now lost and there are no photographs of it. The only thing we have is Smith’s copy of the painting, the “Augsburg aurochs”. “Copy” is a bit misleading, as Smith probably did not track out the original work but made his own version of it. For example, the animal on the original painting had an “entirely sooty black” colour, except for a white chin [1], while Smith decided to paint his aurochs in brown for whatever reason. The black and white version of Smith’s artwork is widely publicised, but the original work is coloured and shows a brown animal as you see down below [2]. 

Wikipedia cites a source which itself cites two sources that the original that Smith’s artwork is based on might not show an aurochs at all: one source claiming the painting might have been based on a hybrid between aurochs and cattle, and another one claiming it might have been based on a Polish steer. 

To see if there is anything legitimate behind these ideas, let’s have a look at Smith’s artwork. We do not know what the original looked like, except for the fact that the original bull was entirely black with a white chin. This is a colour that agrees with the other sources for the colour of the aurochs that we have, only the light dorsal stripe was apparently lacking on the original. This does not necessarily have to mean that the animal the painting was based on lacked a dorsal stripe, since this trait is not visible from every perspective. 

The animal portrayed by Smith matches an aurochs very well in proportions. The trunk is short, the legs are long, the head is large. The horns have the curvature of an aurochs’ horns and face forwards, and also the size is aurochs-like. The ribcage is deep as in the aurochs, and the waist is slender, creating a triangular shape for the trunk, which was very likely a trait of the aurochs as all wild bovines have that kind of trunk. The head has curly hair on the forehead, which is a trait that is well-documented for the European aurochs [1]. The head looks a bit paedomorphic with its concave snout and large eyes, but Smith tended to stylize his animal depictions. The dewlap is very short, as in the aurochs. The animal seems to have a woolly coat, and historic reports say that aurochs were covered in longer hair than domestic cattle [1], which is plausible for a wild animal living in temperate Europe. All in all, Smith’s depiction looks much like an aurochs, except for the wrong colour, which was aurochs-like in the original. It is most parsimonious to assume that the aurochs-like traits found in Smith’s work were also found in the original oil painting, otherwise it would be a big coincidence that Smith’s work happened to be more aurochs-like, in a time when we did not have a very good picture of the aurochs’ life appearance. 

One could argue that the lack of a penis tuft is a hint that the original artwork was based on a domestic steer, as steers usually do not have one. Also, the neck bulge is not very prominent in Smith’s work (steers have none). However, we do not know what the original looked like. Perhaps Smith was not paying attention to these two traits when he did his artwork. Perhaps the artist of the original from the 16^th century did not pay attention to them. Smith’s work, however, definitely shows a scrotum. 

As for the arguments claiming it was a hybrid between an aurochs and a domestic animal, I don’t know what exactly lead the author to conclude that it was a hybrid as I do not have access to the work in which it is postulated. But I cannot derive any possible reasons that lead to this conclusion based on the artwork, because Smith’s aurochs actually looks much like an aurochs and a wild bovine (the morphology, the dynamic pose and the slender waist suggest a wild animal to me). 

Also, the original painting had the word “Thur” written in golden letters on it [1], which is the Polish name of the aurochs. Back in this time, aurochs were only found in Poland [1] and also South-Eastern Europe (Moldavia). The usage of the word “Thur” suggests that the artist had seen an aurochs in Poland, where the last aurochs were found. In Poland, people strictly distinguished between the aurochs and the wisent, because both animals were still found in this country, and they knew what they looked and were like. I see no reason why this word would be used for a domestic steer. 

 

All in all, I think it is highly likely that the original painting Smith’s “Augsburg aurochs” was based on showed an aurochs, that the original probably was a rather accurate depiction of an aurochs because Smith’s work is that too (except for the wrong colour), and that it is well probable that it was painted after a live aurochs. It seems that most authors assume it showed an aurochs, and I see no convincing, compelling reasons to assume otherwise. 

 

Literature

 

[1] van Vuure: Retracing the aurochs – history, morphology and ecology of an extinct wild ox. 2005. 

[2] Frisch: Der Auerochs – das europäische Rind. 2010. 

 

The MAOA gene found to play a role in the aggressive behaviour of Lidia cattle

The monoamine oxidase A gene (MAOA gene) produces the enzyme monoamine oxidase A, which has an important function in the endocrinological metabolism in the brain of mammals. Mutations on this gene cause aggressive behaviour in humans (the Brunner syndrome) and in laboratory mice. These mutations lead to a deficiency of monoamine oxidase A production, causing an excess of serotonin, dopamine and noradrenalin in the brain, which has an impact on behaviour. 

 

A recent study examined the MAOA gene in in cattle. The study tested the MAOA gene in Spanish fighting cattle (Lidia), which is selected for aggression (“fighting spirit”), and breeds that are not selected for aggression and do not display excessively aggressive behaviour (Asturiana de los Valles, Morenas Gallega, Retinta, Rubia Gallega, Avilena, Limousine and Charolaise). They found considerable variation in sequences of the promotor region of the gene between Lidia and the non-aggressive breeds, indicating a possible influence of the gene on the behaviour of the cattle [1]. 

The million-dollar question now is, what were the sequences of the MAOA gene of the aurochs? Was it more like that of Lidia, or even identical as in Lidia, or more like that of the non-aggressive breed or even identical? As the full genome of the aurochs is resolved, it would be very interesting if someone would examine the MAOA gene of the aurochs. It could tell us if this was one of the many key genes that mutated during the domestication of cattle, and what the behaviour of the aurochs might have been like in terms of aggression, although the MAOA gene is probably not the only gene that is involved in aggressive behaviour. 

 

Literature

 

[1] Eusebi et al.: Aggressive behaviour in cattle is associated with a polymorphism in the MAOA gene promoter. 2019. 

 

 

 

Rare aurochs-like traits and the breeds that have them

Some aurochs traits are easy to achieve in “breeding-back”, others are not. For example, it is really easy to breed for a basic aurochs-like colour as this trait is widespread among primitive aurochs-like breeds. Other traits are among the challenges for “breeding back”, also because they are very rare among living cattle. In order to achieve them in “breeding-back”, it is important to visualize where in which breeds these traits can be found. Otherwise the breeding result might not be that convincing in terms of aurochs-likeness. In this post, I mention only the primitive breeds that have some of the desired traits, not the “breeding-back” cattle which already might have some of the traits (f.e. the right body size in the case of Taurus cattle). 

 

Aurochs-like body size. This depends on what you consider an aurochs-like body size. As sexual dimorphism is a factor, I take the withers height of the bulls as a reference. European aurochs bulls varied from 160 to 200 cm or slightly more, therefore they are in the same size class as the wild yak. A number of breeds reach or surpass 160 cm. For example, some Sayaguesa and some Maremmana bulls (such as those acquired for the Auerrind project) reach 170 cm. Chianina and Maltese cattle reach 180 and maybe more in some cases. Modicana from Italy are also said to be 160 cm tall. I know of no confirmed cases, but Podolica and Boskarin might also surpass 160 cm. If one wants to breed for the larger end of the aurochs bull size spectrum, Chianina and Maltese are the only (taurine) options. 

 

Horns with an aurochs-like inwards curve. Horns curving strongly inwards as in the aurochs are found in some individuals of Maronesa, rarely also Sayaguesa. Very rarely, aurochs-like inwards-facing horns are found even in derived breeds such as Holstein (see van Vuure, 2005). Some Lidia also have inwards-curving horns, although their curvature is more two-dimensional compared to that in the aurochs. 

 

Short trunk as in the aurochs. This is a real challenge as this trait is not found in living taurine cattle, at least not in both sexes at the same time. Some Chianina, Maltese and Lidia bulls have an aurochs-like trunk length to leg length ratio, but never the cows. Only in primitive zebus (as outlined in the “challenges” post) have a trunk as short as in the aurochs in both sexes. 

 

Hump as large as in the aurochs. Found in some Lidia and also Corriente individuals. 

 

Elongated skull shape. Found in some Sayaguesa, Lidia, Maltese and Holstein cattle (and possibly others as well). 

 

Well-marked sexual dichromatism. Among the taurine breeds known to me, only Maronesa and the old type of Corsican cattle have a sexual dichromatism as strongly marked as in the aurochs. 

 

Aurochs-like body morphology. Only Lidia has a morphology (in some individuals at least) that looks plausible for a wild bovine, all other breeds have a domestic morphology - some more, others less. 

 

Udder size. The udder should not be visible from the side, as in a wild bovine. This the case in some Lidia and some primitive zebus. 

 

Looking at this list, it appears that for a breeding project that is ought to be successful, well-selected Maronesa, Sayaguesa, Lidia, Chianina/Maltese and primitive zebu are mandatory to achieve a phenotypic match with the aurochs that is as large as possible with domestic cattle. Taurus cattle already achieved many aurochs-like traits such as the right size (cows being 150-155 cm and bulls 155-170 cm tall at the withers), a satisfying sexual dichromatism, aurochs-like horn curvature at least in some cows and the right colour alleles are present (together with undesired alleles). One option would to start from anew with well-selected Maronesa, Sayaguesa, Lidia, Chianina/Maltese and primitive zebu and Watussi for the horn volume. Another option, that might be faster, is to take the best Taurus cattle and breed them for a more homogeneous phenotype, and then cautiously add what may be lacking in the herd, f.e. for the short trunk and small udder adding a F2 individual of (Taurus x primitive zebu) x Taurus that is well-selected, for the horn curvature (if not already achieved by selection with Taurus cattle alone) adding a suitable Maronesa individual, and for the morphology a Lidia individual plus a Watussi or Auerrind crossbreed for horn volume. With consequent breeding, the full potential aurochs-likeness that is achievable with domestic cattle could be seized. One must consider, however, that this would take at least 20 years. 

 

Were European wild horses black or black dun?

Coat colour is the only aspect of the life appearance of the Holocene European wild horse that can be determined with a high degree of certainty thanks to studies examining the coat colour genotype of aDNA samples from wild horses. 

A 2017 study found that the a allele on the Agouti locus, which originated in Iberia in the late Pleistocene and which causes a black phenotype on an E⁺/E⁺ genotype in non-dun horses, became increasingly common among European wild horses in the Holocene until it became the prevalent allele in the later Holocene [1]. This alone does not tell us the phenotype of the animals, because they could have either been black or black dun (also called grullo, mouse dun or blue dun). The question now is: was the late Holocene European wild horse black or black dun?

The Dun locus was resolved in 2015 [2]. It was found that there are three alleles on this locus in horses: dun D, which is wildtype and basal for all living Equus, wildtype non-dun d1 which dates back well into the Pleistocene, and the domestic non-dun d2. 

The black allele was restricted to Europe, it was not found in Siberia so far [1]. The wildtype non-dun allele, on the other hand, was so far found only in Siberia [2]. This could lead us to conclude that there were no horses of a genotype a/a d1/d1, therefore being black. However, it must be considered that the Dun locus was so far only tested for Siberian wild horses, and not for European wild horses. I think it is well possible that there were horses with an a/ad1/d1 genotype, because genetics suggest that during the Pleistocene there was one large panmictic population of wild horses from the Pyrenees to Siberia [3], what makes it possible at least that the d1 allele was also found in European Pleistocene wild horses, which were the predecessors of European Holocene wild horses [4]. Furthermore, some cave paintings might depict non-dun wild horses, such as those at Lascaux, which clearly show black and blackish brown or dark brown horses among a large yellowish-brown horse. This must be viewed with caution, however, because the exact shade of a cave painting is always dependent on the pigments available to the artists and may not necessarily reflect the true colour of the animals. But so far, cave paintings proved to be rather accurate on horse colours. F.e. the leopard spotted horses illustrated at Pech Merle were found to be based on horses having that colour [5], and Ekain also shows black dun among bay dun horses. Therefore, I think it is well-possible that there were black wild horses at least during the Pleistocene. 

This might have depended on another allele as well. Sponenberg & Bellone (2017) state that seal brown, which is a colour found in Exmoor ponies, can be caused by a black phenotype being diluted by the dominant pangare allele Pa⁺[6]. Pangare is a basal equine allele because all living wild equines have it, so it must have been the ancestral state in European wild horses as well and some cave paintings illustrate it very clearly. If seal brown is indeed caused by a black phenotype being diluted by pangare, the existence of black wild horses would depend on if the non-pangare allele pa^np was present in wild horses or not. So far, this has not been tested. I used to think that black suppresses pangare, also because black dun horses always have a dark head while they sometimes may have faint countershading on the body (and as foals sometimes have a white muzzle). The genetic background of seal brown should be tested to be sure. 

Another clue could be historic evidence. There are several records describing free-ranging horses in Europe, and until recently it was unclear whether they were truly wild horses, feral horses or hybrids. A recent study confirmed that they were most likely hybrids of feral domestic horses and the native European wild horses. Go here for a summary of those records on these hybrid populations. What is striking is that black dun horses seem to dominate these reports. Black horses are mentioned only very rarely. Of course, the phenotype of hybrids is not very strong evidence, only a hint, as the domestic horse introgression likely has changed the frequency of the colour phenotypes present in the populations. But black dun is not very frequent among domestic horse breeds. Also, dun in general is less frequent than both non-dun alleles in domestic horses, so that it is unlikely that introgression from dun-coloured domestic horses turned an originally black wild population into a black dun hybrid population. Considering that non-dun is more frequent than dun in domestic horses, I do not think that introgression increased the frequency of dun in the wild population and instead assume that the population was originally dun in most of the individuals. If the original wild population was black, this colour probably would be mentioned much more frequently than black dun in those reports on the hybrids. 

 

All in all, I think the evidence for late Holocene European wild horses being mostly black dun outweighs that for them being black. I think it is well possible that there were black wild horses, at least in the Pleistocene, but more research would have to be done. For example, Holocene European wild horse remains could be tested for the dun and non-dun alleles as much as for the pangare and non-pangare alleles, and the genetic background of seal brown should finally be confirmed. 

 

Literature

 

[1] Sandoval-Castellanos et al.: Coat colour adaptation of post-glacial horses to increasing forest vegetation. 2017.

[2] Imsland et al.: Regulatory mutations in TBX3 disrupt asymmetric hair pigmentation that underlies Dun camouflage color in horses. 2015. 

[3] Cieslak et al.: Origin and history of mitochondrial DNA lineages in domestic horses. 2011. 

[4] Fages et al.: Tracking five millennia of horse management with extensive ancient genome time series. 2019.

[5] Pruvost et al.: Genotypes of predomestic horses match phenotypes painted in Paleolithic works of cave art. 2011. 

[6] Sponenberg & Bellone: Equine color genetics. 2017. 

 

 

 

 

Taxonomy: how to classify domestic animals?

Back in the time of Linnaeus when modern taxonomy was started in 1758, some domestic animals were classified as the members of the species they were derived from, others as distinct species. Taxonomists have been trying to find a universal standard to handle the naming of domestic animals. The main question is: should they be regarded as members of the species they were derived from, or as distinct species? 

Till today, there is no consensus on how to answer this question. Both sides have good arguments for domestic animals either being subspecies of the wild species they derived from or being distinct species. 

 

Arguments for domestic animals being distinct species 

 

Domestic animals have undergone a unique evolutionary path because their evolution is mainly controlled by selective pressures determined by another species, Homo sapiens. Domestic animals have, in contrast to their wild counterparts, experienced a kind of coevolution with humans, and the abiotic and biotic factors of the “natural” (not human-influenced) ecosystem played either only a minor role in the evolution of domestic animals or absolutely none. This is a drastic difference between wild and domestic. Therefore, evolutionary, wild and domestic animals are radically different because the evolution of wild animals is not controlled (influenced, in some cases certainly, but not totally controlled) by humans while that of domestic animals is to a very large extent.

Also, domestic animals differ from their wild counterparts in structure of the genome. The absence of natural selection, the artificial selection executed by humans as well as inbreeding usually leads to a mutation accumulation (often of deleterious alleles) and decrease of genetic diversity, what is called the “costs of domestication”. Thus, domestic animals also differ genetically from their wildtypes. 

Morphologically, domestic animals are distinct from their wild ancestors, albeit the degree differs from breed to breed. For example, a Chihuahua differs from a wolf much more dramatically than a German shepherd dog. But general morphological differences between wildtype and domestic are found in any domestic form. In most cases, the difference in morphology between wild and domestic exceed the differences found between wild subspecies of a wild species. 

One of the most obvious differences between wild and domestic animals is in the behaviour towards humans. These differences are caused by modifications of the endocrinology and neurology, which probably also cause many of the morphological differences between wild and domestic (for details, see the Dedomestication series). 

Due to the absence of natural selection and the more or less intense artificial selection, domestic animals also differ from their wildtypes in physiological aspects. These aspects are directly related to the evolutionary fitness of the animals. I outlined the physiological differences between wild and domestic yaks in this post. A similar reduction of physiological fitness is to be expected in other domestic animals. 

 

Therefore, there are drastic differences between wild and domestic in their evolutionary history and presence, genetics, morphology and physiology. These differences definitely exceed the degree of variation found in wild species that have not been domesticated. Therefore, a status of domestic animals as a distinct species would be justified from an evolutionary, genetic, morphologic and physiologic standpoint. 

 

Arguments for domestic animals being members of the species they were derived from 

 

Domestic animals and their wildtypes are usually able to interbreed without fertility barriers, i.e., they can produce fully fertile offspring. According to Mayer’s species definition, they would be one species because of that. However, Mayer’s species definition does not work universally (for example, wolves, coyotes and golden jackals would be one species because they can interbreed without fertility barriers). 

Another argument for domestic animals being members of the wild species they were derived from is that the social behaviour of domestic animals does not differ from that of their wildtype in most cases when given the chance to life under natural circumstances. 

Also ecologically, most domestic animals are much like their ancestors in habitat preference, food choice and ecologic niche when living under natural circumstances. 

 

It appears that there are good arguments for both sides. It simply is the case that domestic animals are very different from their wildtype on some aspects, and very similar on other aspects. Because of that, I do not think that there will ever be a consensus on how to classify domestic animals. 

Another problem is different domestic animals probably require different solutions. Domestic dogs for example, do not have the same social structure as wolves (as far as I know). Also, ecologically they are not identical. Feral dogs often live as commensals to humans, while wolves do not. So, it might be justified to classify dogs as a distinct species, while many other domesticated animals might be classified as subspecies of their ancestral wildtype. But when not finding a universal standard for all domesticated animals, taxonomy becomes even more arbitrary than it already is. Another problem is that not all domestic breeds/populations are domesticated to the same extent. The differences from the wildtype, be it genomic, ecologic, behavioural, morphologic or physiologic, might be more intense in some breeds than in others. Extreme in some cases, not extreme in others. 

 

This leads to the question if domestic animals should be regarded as taxa at all. Domestic animals are highly heterogeneous, they differ in the extent to which they are domesticated, and often experienced secondary introgression from their wildtype and even other species during their domestication, often only certain populations. In some cases, it even is questionable if all members of a domesticated form can reproduce with each other under natural circumstances due to physical barriers (such as in the case of Chihuahuas and Irish Wolfhound). Maybe it would be better to give domestic animals no taxonomic status at all, but rather regard them as inhomogeneous, artificially created populations of certain wild animals that have been domesticated to a varying extent – varying when comparing different domestic forms to each other (f.e. horses versus dogs) as much as within the domestic forms (f.e. Spanish fighting cattle versus Fleckvieh).