I have been running this blog since 2013 now, which is 13 years. After exactly one and a half decades of collecting info on the aurochs and wild horses (I started getting into this topic in 2011), my conceptions of what I consider the most likely scenario based on the available evidence on a number of topics shifted. With this post, I want to give an overview over where my opinions or assumptions changed in the last 13 years, especially as some very old blog posts show outdated assumptions of mine. I try to put disclaimers on every blogpost that I consider outdated and link to an up-to-date article, but with my 550+ blogposts, it takes a while. So, here is a comprehensive list:
- The neck muscles in aurochs bulls
Taurine domestic bulls all can have two kinds of neck musculature: either a so-called “crest”, where the neck forms a bulge that is separate from the shoulder hump (if present) or a neck that is still very muscular but with a smoother transition to the shoulder hump. Prime examples for these different bull necks are Lidia and Sayaguesa. The former has the first described neck shape, the latter one the latter. The length of the dorsal spine seems to play no role in this, it seems to depend on the development of the musculature. This begs the question: what kind of neck shape did the aurochs have?
Looking at extant wild bovines, we see both kinds of necks, but dependent on the species. Gaur have a neck crest, Banteng have a less developed neck musculature. Wisent have a neck crest, while American bison have the neck merging with the shoulder hump. So phylogenetic bracketing is not useful to resolve this question. So I reasoned until a few years ago that the hormonal changes from aurochs to domestic meant that aurochs had more testosterone, and the M. trapezius is particularly testosterone-dependent (partly). So I figured that the neck crest is more likely for the aurochs. I no longer uphold this reasoning. First of all, there is no direct evidence that aurochs bulls had higher testosterone than domestic bulls, however likely it may be. Also, the testosterone level is not the only factor influencing the amount of the muscle tissue, it is also the number of androgen receptors to which the testosterone binds that plays a role. Hence an aurochs bull could have had a much higher testosterone level than a domestic bull with a crest and still have no crest. So this reasoning was not suitable to determine if aurochs bulls had a “Lidia neck” or “Sayaguesa neck”.
Also, cave paintings and other contemporaneous artistic depictions of aurochs bulls are unambiguous in this respect: they all, and I mean all, show a “Sayaguesa neck”. Hence, I was wrong on the assumption that aurochs bulls must have had a neck crest.
- The mane of European wild horses
I no longer believe that European wild horses had a falling mane like domestic horses. I used to think that because of the claim that the Equus caballus lambei carcass has a falling mane, but that one has never been properly described. And even if it had a falling mane, it would not be possible to implicate a falling mane in European wild horses by phylogenetic bracketing, as lambei is more distantly related to those than is the Przewalski’s horse. Also, a Equus caballus lenensis horse carcass has a very short mane of only 15cm, which was probably standing. Furthermore, Iberian wild horses are even more distantly related to domestic horses than Przewalski’s, therefore their mane was very likely standing. And, not to forget, all cave paintings show horses with an upright mane. Domestication also caused a hanging mane in some donkey breeds, so we can be rather sure to assume that the falling mane is an artefact of domestication in horses too and that European wild horses had a standing mane.
- Hybridization with wild bovines in “breeding-back”
When I started the blog, I was opposed to the idea of hybridization with existing wild bovines for “breeding-back”. I thought that this would introduce many undesired traits not only to morphology, which is the lesser problem because it is easily “visible”, but also concerning behaviour and ecology, which are rather tricky to select against. However, nowadays I think that if the doses are small enough and if the hybridization is carried out with a meticulous selection scheme, introducing suitable species can be very beneficial to “breeding-back”, and if done in an experimental population with its own herd book, there is no way this can do harm. The species I am considering are (Java) banteng, wild yak and nowadays also wisent.
- Certainty with which we know the aurochs’ life appearance
I used to think that the life appearance of the aurochs is well-resolved. We have living descendants and close relatives for extant phylogenetic bracketing, we have historical texts describing the animal that match with ancient art. However, nowadays I think it is not that easy. For example, if domestic cattle display a certain peculiar trait that is not found in wild bovines, it cannot easily be assumed it is an artefact of domestication. An example would be the somewhat sloping backs of many domestic cattle. Wild bovines tend not to have that (except in certain positions when they stretch their hindlimbs, so that the back is sloping), and some domestics have it pronounced extremely. I saw no functional benefit to this trait and thus I assumed that aurochs had a strictly horizontal lumbar spine, as do extant wild bovines. However, almost all ancient art shows aurochs with sloping backs. The skeletons do not help us in determining which posture is that of the aurochs, since this would mainly depend on the length of the ligaments and muscles in questions. Thus, we don’t know but I am inclined to think they had a somewhat sloping back. But we cannot be sure. Another point is blond or red hair between the horns; many wildtype-coloured bulls have them, historic texts never describe them and one belt made of the skin between the horns of an aurochs with the fur still attached was black. However, this is not a large sample size at all. And we do not have that much historic texts speaking of the forelocks, actually only three (Schneeberger, von Herberstein and Swiecicky). This can barely account for a possible variation spectrum, if there was one. We don’t know. The same goes for a lightly-coloured saddle in European bulls. Evidence only points against such a trait in males, but I recently reported that there is one cave painting that might be interpreted showing a bull with a light trunk. These are just examples; although the life appearance and morphology of the aurochs is comparably well-resolved, it is not completely resolved. I’d say somewhere between 80 and 90%.
- Bulkiness of the aurochs
This could actually be included in the upper point but I mention it separately because this does not necessarily only depend on species-specific aspects. The bulk of a bovine depends a lot on how well it is fed and therefore also the seasons (this is even mentioned in Schneeberger’s text on the aurochs), but also the age – bulls in particular, even in wild bovines, can grow extremely hefty with age. I often used young Lidia bulls as orientation for my bull reconstructions, mostly because I always feared making my aurochs too bulky would make them look “domestic”. But Lidia bulls are, when allowed to get fully developed, actually very massive. Von Herberstein’s illustration of his stuffed specimen shows a very massive animal that looks basically like a sausage. And this is compatible with a number of cave paintings and engravings, such as the one from Grotta del Romito or Dordogne. So I underestimated the bulk of fully grown aurochs bulls in the past, mainly because I did not want to fall in the pitfall of many artists reconstructing the aurochs of making it look like a domestic bull with aurochs horns and colour. So I fell in another pitfall.
- My aurochs reconstructions
Nowadays I think some of my earlier reconstructions of the aurochs are inaccurate in some respects, mainly because I exaggerated the morphology unintentionally when I tried to appreciate the fact that it was a wild bovine and not a domestic one. I am still trying to figure out some anatomical details, it is a learning process and also open to a lot of interpretation.
- The reliability of cave paintings
I never dismissed cave paintings as a source completely, especially for colour. But for morphological aspects, I considered them to be too stylized or imprecise to be used as a strict guideline. This may still be correct as a whole but I think if all cave paintings, in their imprecision and stylization, show a certain anatomical trait independently, it should be taken seriously. For example, it seems the dewlap of the aurochs was shaped differently from that of domestic cattle and more similar to that of banteng and steers. Also, only few cave paintings support the super-athletic morphology of my reconstructions that were based on young Lidia bulls, they all, or many, show rather bulky animals. Also, many of them show rather longish bulls, which makes me wonder how much the intervertebral discs of the spine added to the trunk length of the skeleton in the living animal, which ties to the point of uncertainty about the morphology of the animal.
- Zebu hump in the Indian aurochs
I was completely unsure on whether a zebu hump was already present in Indian aurochs or not, tending to reject the idea based on the literature I found that claim no function for the hump has been determined yet. It seems though, as several breeders of indicine breeds have told me, that the fat deposit that surrounds the hypertrophied M. rhomboideus that forms the hump gets much fatter during summer and decreases almost to nil during winter. This is actually a common strategy in ruminants to deal with the seasons: to acquire a surplus during summer when food is abundant and living on the fat storage during winter. That’s why free-ranging cattle often look very skinny during winter but “recover” just fine. Now, India does not have winter in the sense of snowfall, but its vegetation is heavily monsoon-dependent and goes through a severe dry phase every year. And concentrating the fat storage in one spot instead of dispersing it around the whole body would actually be efficient in a hot climate from a thermoregulatory aspect. So it might indeed be possible that the Indian aurochs did have a zebu hump and that it had a function.

New little sculpture I made of Bos taurus namadicus with a hump, based on the GIS skull.
- Usage of the name “tarpan” and Equus ferus
There is so much confusion around the word “tarpan”. It started as a local, colloquial name for local free-ranging horses which may or may not have been wild or at least partly wild horses. Then it got transferred, after the extinction of these populations, by some authors onto what they considered wild horses of Europe. This got adopted by many later authors of the 20th century, reframing the usage of a local term for horses of dubious nature in the southwestern Eurasian steppe in the 19th century to a synonym of the original western Eurasian wild horses, creating the false impression that it was the colloquial name for this animal in Europe, which never was unambiguously the case. There is a chance that the horses historically called tarpan were wild horses with only minor admixture from escaped domestic horses, but we cannot verify this. Therefore, using this local historical term for the biological wild horse of Western Eurasia is not wise.
Very, very widespread is the use of Equus ferus for the species of the wild horse. This is actually ill-grounded, even if you consider wildtypes species distinct from their domestic descendants. Equus ferus does not have a type specimen, not even a lectotype. It is loosely based on a written description of free-ranging horses encountered by Gmelin in the 18th century. Gmelin spotted a free-ranging herd of horses consisting of what he considered wild horses, a mare he recognized as domestic plus her hybrid foal. I see no compelling reason to regard Equus ferus as suitable for qualifying as the binominal name for the wild horse, not at all. I think the adoption of this name for the species of wild horse was a poor decision by later authors. In fact, the first binominal name that was unambiguously based on a wild horse with a type specimen is Equus przewalskii. Therefore, if you regard wild horses as a species distinct from their domestic descendants, you would have to refer to them as Equus przewalskii, not Equus ferus. If you consider wild and domestic horses one species, this species would unambiguously have to be referred to as Equus caballus.
- The purity of the last wild horses in Europe
This will remain a matter of debate forever, as historic texts are not definite enough to be sure about the nature of the last remaining free-ranging horses western to the Ural river. However, genetic evidence points to at least some of them being partly a distinct ancient wild horse strain, and there is even the chance that the very last “tarpan” kept at the Moscow zoo was “pure” or hat only minor domestic influence. I go over this in great detail in my book available on amazon.
- Usage of Bos primigenius
I used to prefer Bos primigenius over Bos taurus for the species of aurochs and cattle because the former has a holotype and the latter does not. However, following the rules of the ICZN very strictly actually Bos taurus has priority over Bos primigenius because opinion 2027 does not apply: Linnaeus described both the aurochs and cattle under Bos taurus in 1758, he explicitly mentions the “ferus Urus Poloniae”. Thus, Bos taurus is not a senior synonym of the aurochs based on its domestic counterpart, in which case opinion 2027 would apply, it is the aurochs and always was. This was just overlooked by later authors, possibly because many considered the “urus” to be identical to the wisent until Bojanus 1827.




