I own an aurochs horn now: what it tells us

Recently I purchased an aurochs horn from most likely or at least the 15^th century. It is not only the only one in private hands known, but also the largest aurochs horn sheath known and beautifully preserved. It is from a private collection and was inherited by Daniel Vanackere who gave me the opportunity to purchase it. His family owned the horn for centuries in Rotterdam. Very, very big thanks to Daniel Vanackere to give me the opportunity to acquire the horn! 

 

Here it is:

It measures 134 cm at the outer bow, 13,5 cm at the anteroposterior diametre, 11 cm in dorsoventral diametre and 41 cm in circumference at the base. The beauty of this horn is that it is almost completely unmodified, just one or two centimetres at the base seem to have been cut off and there is an attachment for what might have been a belt that was attached onto the horn in the 15^th century. Most putative aurochs horn sheaths that we see are sanded down and polished, and the tip is often cut off (see here for example). My horn is completely the way it was on the living bull, except for a slight discolouration on the surface as it is 500 years old. But one can still recognize where the blackish tip starts and where the yellowish part of the horn was. 

 

I think it is highly likely that it is from a pure, mature male aurochs. I think so because of the curvature (yes, the tip curves outwards but read on), the dorsoventrally compressed horn base (a trait very expressed in Pleistocene aurochs, less so in Holocene aurochs and not in most domestic cattle), the size, the thick base and the very slim tip (a contrast less expressed in domestic cattle) and the keel on the ventral side of the horn (a keel on the horn is a very ancient trait in aurochs, most common in the Indian aurochs and some zebu). 

Concerning the curvature, we should consider that of most aurochs horns only the bony cores are preserved while sheaths that definitely are from pure aurochs are very rare. I wanted to know what the bony core of the horn would have looked like and so I made a “cast” of partly plaster, wire and tissue paper, and this is the result: 

As we can see, the bony core has a perfect aurochs shape and with 70 cm it also fits in dimensions. It is just that the horn tip does not follow the curvature of the bony core, but makes a turn and curves outwards-forwards. I have been puzzling about that. I assumed that maybe there was much more variability in the shape of the horn sheath than the bony cores suggest. My first thought to that assumption was: but the depictions of aurochs all show inwards-curving horns. But then thought further and it came to my mind that there are actually quite a few aurochs depictions with lyre-shaped horns. For example, this one from a chalcography from 1596, showing an aurochs hunt in Bavaria: 

Scan from Walter Frisch's Der Auerochs, original photo by Museum Karlsruhe

Or the famous depiction in Siegismund von Herberstein’s book showing his aurochs taxidermy:

It is usually assumed that the horns in this depiction were simply invented by the artist and that they were lacking in the taxidermy. However, it shows the wavy surface of my horn and the shape is compatible as well. 

 

And then there would be the depiction of the African aurochs in Beierkuhnlein 2015 [1]. 

 

In the past, I did not put much emphasis on the depicted lyre-shape of the horns, assuming that the artists did not pay much attention to the actual horn shape or that they invented the horns, or did not see life aurochs in real et cetera. But looking at my horn, I see that differently now. I have no idea how common such an outwards-curving tip in the aurochs was, it could have been 1%, 10%, 80% of bulls, everything is possible. 

 

How does the horn fit with other preserved aurochs horn sheaths? First of all, it is its incredible size that sticks out. Medieval aurochs horns usually are not nearly as large as those of earlier ages, particularly the Pleistocene. But this one is. Also, late aurochs had a quite round horn base, much more like domestic cattle than earlier aurochs. But mine has a dorsoventrally compressed horn base, as a Pleistocene aurochs would. Also it has the keel on the ventral side which I haven’t seen in any other putative aurochs horn sheath yet. So morphologically, my horn fits much older aurochs better than other aurochs horn sheaths from the medieval times onwards. How can that be interpreted? I see several possibilities: a) the sample size (some dozens of sheaths) is too small to correctly determine the variability of very late aurochs horns, b) my horn is much older than the 15^th century c) the other putative aurochs horn sheaths are from aurochs that were hybrids with domestic cattle and my horn is one of the very few, or perhaps the only one, preserved that is from an aurochs free or almost free of domestic influence. 

I tend to favour explanation c. The sample size is not that small, I have seen at least 20 sheaths so far. And all of them are rather small by aurochs standards, except for my horn. Explanation b would require that the horn somehow survived that well preserved a very long time, which makes it unlikely that it was found in turf, permafrost or soil as it would now be discoloured which it is not. The only scenario I can think of is that the horn has been in human hands since, for example, the Roman times and got passed on by generation to generation. But I don’t know if that scenario is plausible. 

But there is considerable reason to assume that many very late aurochs populations were actually hybrids with domestic cattle. Hybridization in both directions between cattle and aurochs has been found on the Iberian Peninsula [2]. A study examined 7 putative aurochs horn sheaths genetically, and it was found that 3 of them have domestic cattle mitochondria, including the horn of the last bull from Jaktorow from 1620 (which is only 46 cm long and very weakly curved, with the base and the tip being almost equally thick) [3]. That the other ones have the P haplotype does not rule out introgression from cattle as some cattle have that haplotype and it does not tell us anything about the nuclear genome. 

 

I assume the horn belonged to a bull because of the thick horn base and the size of the sheath. It could be that it was an old mature bull, since horns continue to grow until death and the tip is very long (it makes up 48% of the length of the horn). Old bulls are solitary and do not fight for mating rights anymore, so they could effort to have that long and thin horn tips. I estimate the bull was 15 to 20 years old at time of death. I would like to know the story of that bull, and the precise locality where it died.  

This is what the set of horns might have looked like on the living animal: 

This of course makes me wonder how large the bull was. I tried to calculate the withers height of the bull using photos of two very large-horned specimens, the Etival and the Sassenberg bull. I calculated the relative size of the horn diametre at the base to the withers height and multiplicated it with the diametre of my horn. The result was 190 cm. Considering that I used skeletons as a reference that would have been surrounded by soft tissue in the living animal, the bull might have been between 195 and 200 cm tall at the withers in life. 

 

 

I am sure some of you will be familiar with the curvature of the horn. Many Maronesa cows, some Sayaguesa cows and also many Tudanca (in this breed also the bulls) have a horn curvature that is very similar to that one. I used to think that these outwards-forwards curving horn tips are a domestic mutation, but my horn changed my perspective on that. It seems possible that this is part of the variation of the aurochs, and has been preserved in breeds such as Maronesa and Tudanca. 

 

I think this underlines the preciousness of Maronesa. It is the only breed still in existence that I know of that has a colour that 100% matches that of the European aurochs, with a well-marked sexual dichromatism. It is also one of the very few breeds that has strongly inwards-curving horns and it seems that the corkscrew-like curvature seen in many cows is part of the natural variability of the aurochs. A Maronesa-Tudanca lineage could maybe reproduce the curvature of my horn precisely. 

 

Literature 

 

[1] Beierkuhnlein, 2015: Bos primigenius in ancient Egyptian art. 

[2] Günther et al.: The genomic legacy of Human management and sex-biased aurochs hybridization in Iberian cattle. 2023 (preprint). 

[3] Bro-Jorgensen et al., 2018: Ancient DANN analysis of Scandinavian medieval drinking horns and the horn of the last aurochs bull. 

 

 

 

Awesome photos of awesome Tauros cattle

I am always excited when I see new photos of Tauros cattle, because I have not yet had the opportunity to visit any of the herds of the project. Bert van Beek has lots of great photos of very interesting Tauros cattle on his Instagram page: https://www.instagram.com/bertvanbeekphotography/

 

Have a look at the photos, I like the cattle very much. One cow seems to be a Maronesa x Maremmana, the cow with the huge lyre-shaped but forwards-facing horns. Another one seems to be Sayaguesa x Maronesa and has a perfect horn curvature. I think an (F2 Maronesa x Sayaguesa) x (F2 Maronesa x Maremmana) would have great potential, especially an F2 from that combination. I think some of the photos show Manolo Uno, the Maremmana x Pajuna bull that was born at the start of the project, but it could also be a bull of the same combination. One bull has a really large hump, a characteristic that quite a few Tauros bulls have. 

 

It would be extremely awesome if all of the current projects would one day cooperate in some sort by exchanging individuals once all of them have reached a similar level of quality as an aurochs substitute. 

Two of my aurochs sculptures are for sale

I have to create more space in my sculpture room because I keep on having new ideas, therefore some of my aurochs sculptures are available for sale now. 

Both of them are made from air-drying modeling clay and painted with acrylics. 

Sculpture of the Sassenberg bull 

- 32,2 cm withers height, 55 cm long, 21 cm horn span 

- Body morphology based on the Store-damme skeleton, skull and horns based on the Sassenberg bull

Sculpture of an Indian aurochs bull 

- 28 cm withers height, 49 cm long, 25 cm horn span 

- Body morphology based on the Store-damme skeleton, skull and horns based on the cranium at the Geological Survey of India 

If you are interested in one of the sculptures or both, feel free to contact me at daniel.foidl@itmed.at 

What the aurochs really looked like (new reconstruction)

Last week, I finished my latest aurochs model. Just like the previous one, its postcranial morphology is based on the Store-damme skeleton, the head on the Sassenberg bull and the London skull; the horns on the Vig bull this time. This is the result: 

I think this time I accomplished it to provide a plausible, life-like picture of what a living aurochs bull most likely looked like. I am very happy with the result. It is 33 cm at the withers tall, therefore 1:6 scale for a 200 cm aurochs. 

I also started a new model, a male African aurochs, based on osteological material and what Egyptian artworks suggest what its colour was like. I promise you that it will be quite surprising. 

Magnificent young Auerrind bulls

Recently, Felix Hohmeyer posted photos of young bulls from the Auerrind herd near Bielefeld on Facebook: 

© Felix Hohmeyer

© Felix Hohmeyer

The upper one is a son of Apollo (Maremmana x Watussi) and a Sayaguesa cow, the bottom one is the (Sayaguesa x Grey) x (Sayaguesa x Watussi). I have to say I am very happy with those bulls, they look great. They were born in 2022, so they are still young, but their morphology, colour and horns look very promising. The cow in the background of the bottom photo seems to be part Chianina, I would say the ideal mating partner for those bulls. I think the Auerrind project is progressing extremely well and I am very much looking forward to seeing those animals fully grown and their future offspring. 

I am writing a book on "breeding-back"

During the last 3 years, I have been writing a book on “breeding-back” and everything related to it. Basically compiling all the knowledge and literature I have been gathering on this blog over the last 10 years. The bulk of the work covers the aurochs, but also of course the wild horse and the quagga is covered as well. 

 

In this book you will find everything I covered on this blog in a structured and comprehensive manner, and also of course new information. It will feature: 

-       An overview over the impact of large herbivores on the landscape 

-       A precise description of what we know about the aurochs 

-       How domestication changed the wild bovine

-       A history and evaluation of and ideas for “breeding-back” the aurochs in as much detail as possible 

-       A precise description of what we know about the wild horses of Europe 

-       A compilation of historical evidence of the horses historically called “tarpan” 

-       A critical evaluation of the stories revolving the Konik pony, Exmoor pony and Sorraia 

-       Ideas for a “breeding-back” project focusing on horses 

-       The quagga and “breeding-back”

-       My dedomestication hypothesis

-       Thoughts on the potential de-extinction of recently vanished megafauna 

-       qualitative photos and artworks, some of which I have not published so far 

 

I hope to publish it within next year (2024).

Why I think purity makes no sense in "breeding-back"

Readers of my blog will know that I am not afraid of proposing mixing “breeding-back” cattle with less-derived zebu breeds and even different species such as the wild yak and the banteng. Some might object that this would undermine the “purity” of those cattle as domesticated Bos primigenius primigenius. This is, however, not a concern to me, for a number of reasons that I want to outline with this post. 

1. Hybridization/introgression is common in evolution 

With our increase in genetic knowledge, we have more and more cases of closely related species that experienced more or less intense introgression from each other through hybridization. I have the impression that introgression was found everywhere it was looked for, including our own genus Homo. So we can assume hybridization is a quite common factor in the evolution of species. Bovines are no exception to this, including the aurochs, where hybridization between bison and aurochs has been found in both directions (albeit the gene flow was comparably small), and I would not be surprised at all if gene flow was also detected between aurochs and banteng and between wild yak and aurochs.

2. Domestic cattle are already highly mixed between the different lineages of Bos primigenius 

The initial domestication events, as far as current knowledge goes there were two of them, concerned B. p. primigenius and B. p. namadicus. However, the resulting domestic lineages did not remain pure domestic descendants of those respective two subspecies, as there not only was introgression between them, from taurine to indicine and vice versa, but also introgression from other aurochs subspecies. The mitochondrial haplotype R was likely inherited from the African aurochs, and recently Hereford has been found to have traces of introgression from B. p. suxianensisfrom Mongolia. This introgression was probably not limited to this one breed, it just was detected there. Therefore, taurine cattle are a mix of all four mainland aurochs subspecies, and zebus possibly too, as they experienced gene flow from taurine cattle, especially in recent decades. Therefore, the remaining aurochs alleles from the four mainland subspecies are not found in four distinct domesticated lines, but are most likely all over the place in taurine and indicine cattle. 

3. Zebus share alleles with the European aurochs that taurine cattle do not have 

When the full genome of a Neolithic aurochs bull from Britain was resolved by Orlando 2015, it was found that zebus actually share some alleles with the European aurochs that taurine cattle do not have. Less-derived zebus also are more aurochs-like on some aspects than most taurine cattle, such as the trunk length and leg length, udder size and overall slenderness. Whether there is a connection between those alleles shared with the European aurochs and these phenotypic traits has not yet been investigated, those alleles could be responsible for any biological aspect of the organism. Therefore, if one wants to come as close as possible to the European aurochs, including less-derived zebus into the breeding would be wise, even if it sounds counterintuitive at first because they descend from a different aurochs subspecies. 

4. Some wild bovines might share alleles with the aurochs that domestic cattle do not have 

Just as zebus share alleles with the European aurochs that taurine cattle do not have, it is possible that living wild bovines might have some wildtype alleles found in the aurochs that cattle have lost. This might particularly be true of alleles for morphological traits that are likely homologous, such as the primigenius spiral (found in the wild yak) or a well-marked sexual dichromatism (found in the Java banteng). Thus, including these wild bovines into the breeding might be very beneficial to “breeding-back”. Species purity in the “breeding-back” results is not really a concern to me as long as the introgression is limited to genes for desired key traits, because taurine cattle are not “pure” European aurochs anyway but rather a composite of an unknown portion of mutated alleles and remaining wildtype alleles. The same goes for zebus in respect to the Indian aurochs. 

 

Thus, I would not be afraid of mixing lineages in “breeding-back”. Taurine cattle are already highly mixed, and they lack some traits and alleles that can only be effectively reintroduced by mixing lineages and selecting wisely. Note that I am not opting for rampant crossbreeding and hybridization, but rather to use small doses of introgression accompanied by targeted selection in order to keep the desired traits from each lineage and eliminate distinctive traits of the other lineage. This goes for morphological as much as behavioural, ecological and – to the degree that it is detectable – genetic traits. This way, aurochs-like bovines that blow our minds could be achieved, while that is very difficult using taurine cattle only. 

 

 

European and Indian aurochs may have vocalized differently

Recently I learned on a Facebook group that taurine and indicine cattle vocalize differently. Previously, I had assumed that all cattle vocalize in the same way, and that that way is typical for the entire species of Bos primigenius. It turns out that there are differences between the vocalization of taurine and indicine cattle, and I suspect those differences could be inherited from their wild ancestors. 

Taurine bulls often make repetitive, trumpeting calls: 

Zebu bulls, on the other hand, omit growling grunts, resembling the roar of a jaguar: 

I find this fascinating. I consider it quite likely that both calls are inherited from the European and Indian aurochs respectively, although we cannot rule out that mutations affecting behaviour during domestication created this difference in vocalization. 

Trunk length of the aurochs and the mysterious Cambridge specimen

In Cis van Vuure’s classical Retracing the aurochs it is written that the shoulder height of the aurochs nearly equaled the trunk length, in contrast to most domestic cattle where the trunk is longer. Somehow “nearly equals” became “equals” in my memory, although I read the book several times and it also cites a source that gives precise data, namely that the height of the withers to the trunk length ratio varied 1:1,02 to 1:1,1. One has to be cautious, however, because the withers height is influenced by the length of the spinal processes in the shoulder region, which may vary from individual to individual and differs between the sexes. So calculated the ratio between the height of the upper margin of the shoulder blade and the trunk length using photos of 10 aurochs skeletons in lateral view. 

There is also a written remark of the trunk length of the aurochs by a person who visited living ones, Anton Schneeberger. He states in his letter to Conrad Gesner that the cows are “not as long” as the bulls. 

 

Specimen	Sex	Ratio of shoulder blade height to trunk length
Braunschweig	male	1:1,14
Friemersdorf	male	1:1,11
Hammerslöv	male	1:1,15
Prejlerup	male	1:1,06
Sassenberg male	male	1:1,17
Store-damme	male	1:1,17
Vig	male	1:1,11
Sassenberg female	female	1:1,03
Cambridge	? female	1:1,19
Mönchengladbach	? female	1:1,17

 

The Sassenberg cow is the only mounted specimen of the European aurochs which I am highly confident that it is from a cow, because of its entire morphology. For the Mönchengladbach and Cambridge specimen, I am not so sure. Especially the Cambridge one puzzles me. The morphology of its postcranial skeleton resembles that of unambiguously male specimen, such as the Prejlerup specimen, f.e. because of the relatively long and massive spinal processes in the shoulder region. The skull, however, looks very feminine compared to definitely male skulls such as the London one, because of its barely protruding orbital bosses and the overall gracile build. Also, the Cambridge skeleton is merely 145 cm tall, what would be 150-155 cm in life, which is suggestive of a cow, particularly from Northern Europe. 

The Sassenberg cow has the shortest trunk, barely longer than the height of the shoulder blade. This fits the historic description by Schneeberger. As it happens, the Cambridge specimen has the greatest relative trunk length. This could have various reasons: 

- The Cambridge skeleton is from an – extraordinarily small – bull  

- Trunk length is not a reliable indicator of sex in the aurochs 

- The sample size is too small to determine anything 

Actually, I consider the third reason the most likely one. Guessing by eye, it was always my impression that in domestic cattle the cows are shorter than the bulls too, but I have no reference at hand confirming this. It would be interesting to investigate this thoroughly with osteometric measurments. 

New photos of the Watussi-influenced Auerrind cattle

 Here are some new photos of Watussi-influenced Auerrind cattle: 

© Yannick Weinand

These photos show the Watussi x Chianina cow. It is interesting to see its phenotype develop, as this combination bears a huge potential for future crossbreeds.

 

All the subsequent photos are © Claus Kropp

This is the (Sayaguesa x Hungarian Grey) x (Sayaguesa x Watussi). It looks great, it has a perfect aurochs colour and a very long snout, much of the Sayaguesa-appeal. 

This cow is the Chianina x (Sayaguesa x Watussi). Her morphology is very good, and her light but not diluted colour endorses the suspicion that Chianina has some degree of sexual dichromatism masked by the dilution alleles. Also the snout is very long. 

This is one of the Maremmana x Sayaguesa cows with the Sayaguesa x Chianina bull behind it. This combination bears good potential, Chianina and Sayaguesa bring the size, Maremmana horn length and a good winter coat. 

This young bull is (Watussi x Sayaguesa) x (Watussi x Chianina). It's great that this combination exists, it has the potential for tremendous horns and the colour is right as well. 

This is the (Sayaguesa x Grey) x (Sayaguesa x Watussi) bull, a combination which I think bears great potential. The horns seem to grow huge, especially considering that the bull is not even 3 years old (!). 

I have to say that I am very happy with how the Auerrind project is progressing. Those are great animals with a lot of potential for even better future crosses.

Fascinating news: Mongolian and Iberian aurochs influenced cattle; another dwarf aurochs described

The last few months saw the publication of three very interesting papers on the aurochs. One analyzed ancient genomes of Mongolian aurochs and found that it influenced ancient Mongolian domestic cattle, an influence that lives on in a breed you would never expect. Another one analyzed bovine material from the Holocene of Spain, and found significant introgression from Iberian aurochs into cattle. The third paper describes another aurochs dwarf form or subspecies, this time from a Greek island. 

-) Mongolian aurochs influenced Mongolian cattle 

Aurochs material from Mongolia was analyzed and all of them had the mitochondrial haplotype C (which was also found in Chinese aurochs assigned to B. p. suxianensis and is distinct from the European haplotypes). It turns out that B. p. suxianensis influenced local Mongolian cattle, which is what I expected because I consider it very likely that introgression from wild to domestic occurred anywhere aurochs and cattle lived side by side. However, modern Mongolian cattle are different from ancient Mongolian cattle. In modern cattle, Mongolian aurochs influence was detected Hereford. This is rather surprising. 

In the phylogenetic analysis, haplotype C is a sister group to the western Eurasian haplotypes, forming a clade that is a sister group to haplotype R, which was found in African aurochs. The Indian haplotypes (from zebu) are an outgroup to all the other haplotypes of the species detected so far. This indicates that the European aurochs was closer to the East-Asian aurochs than to the African aurochs, and that the Indian aurochs was the result of the first cladogenesis event in Bos primigenius that we know of. 

Brunson et al.: Ancient Mongolian aurochs genomes reveal sustained introgression and managment in East Asia. 2023 (preprint) 

-) Iberian aurochs influenced western European cattle 

Archaeological material from the late Holocene of Spain was analyzed and the fully resolved British aurochs genome used as a reference for pure aurochs. It was found that some remains were up to 90% aurochs, others as low as 20% and the rest, respectively, domestic. This indicates that domestic cattle and aurochs hybridized frequently, leading to introgression to both wild and domestic populations. The data suggests that male introgression from aurochs was more common than female introgression, which is something that I expected because of the handling of cattle back in early days. They were kept free all year round, where wild bulls could have easily mated with domestic cows - a behaviour that is also historically documented (Schneeberger). It gets even more interesting: The genomes of modern western European cattle breeds are between 20 and 25% aurochs. Lidia was also tested, but did not show a higher portion of aurochs. The authors, however, speculate that the aurochs material preserved in Lidia might be key genes for behaviour and appearance, explaining the high degree of similarity between aurochs and Spanish fighting cattle. I too consider this highly likely. 

Günther et al.: The genomic legacy of Human management and sex-biased aurochs hybridization in Iberian cattle. 2023 (preprint). 

-) Bos primigenius thrinacius 

Previously to the new paper, two insular dwarf aurochs subspecies were described: B. p. siciliae on Sicily and B. p. bubaloides on Pianosa, Pleistocene of Italy. There are also remains from Malta which may constitute a third insular subspecies that has not yet been formally described. Now another one, from Kythera Island, Greece, has been described. It seems to be the smallest of the dwarf aurochs, slightly smaller than B. p. bubaloides, which had a withers height of 100-120 cm. No complete skeleton of B. p. thrinacius has been recovered, unfortunately. But what is known seems to suggest that the sexual dimorphism was reduced, and there was a tendency to loose premolar 2 in the dentals preserved. The dentals also look comparably short to me by aurochs standards. I would say this is in line with general tendencies of insular mammals to show signs of paedomorphy, similar to domestics. The study was co-authored by Roberto Rozzi, who did a lot of interesting research on insular bovids. 

Siarabi et al.: Insular aurochs (Mammalia, bovidae) from the Pleistocene of Kythera Island, Greece. Quaternary Science Reviews (2023). 

How (not) to quantify aurochs-likeness in cattle

I have been trying to quantify aurochs-likeness in extant cattle multiple times and it turned out to be very difficult. It starts with the question of what is a “trait”. For example, is coat colour a trait or is it rather a complex of many traits (what types of melanin are expressed, where they are expressed et cetera)? Some traits also interfere with each other. As an example, leg length (i.e. proportions) influences height and other parameters. If a short-legged bull is only 150 cm tall, it is shorter in height than the European aurochs. If it had the right leg length it might be 20 cm taller, meeting the height of some European aurochs. Is, considering that, both the body size of the animal and the leg length deficient, or is only the leg length deficient? Even more problematic is the thought that not all traits are regulated by the same number of genes. Colour is regulated only by a handful of genes, perhaps roughly a dozen, while the bodily morphology is much more complex and influenced by many genes (I assume so because endocrinology influences the body morphology quite dramatically, and the hormone system is influenced by a very large number of genes). So which cattle individual is more aurochs-like, i.e. closer to the aurochs, one that has the right colour but a totally domestic morphology, or one that has the right morphology but deviant colours? If every defined “trait” (what is a trait?) is assigned an equal value, both individuals would be equally aurochs-like. This neglects the fact that in one individual a lot of genes are “right” and only a handful “wrong” while in the other a lot of genes are “wrong” and only a handful “right”. Therefore, the most objective and useful way to compare the phenotypic aurochs-likeness would be to compare every single gene that has an influence on the phenotype. This is practically near impossible as mammals have between 20.000 and 30.000 genes and we do not know the phenotypic impact of every single allele on every single gene. Therefore, an attempt to quantify even the solely phenotypic similarity to the aurochs necessarily has to be somewhat simplistic. I made lists of aurochs-like traits and scored a number of cattle breeds for those traits, each time a slightly different approach and the result always was that Sayaguesa and Lidia were among the two most aurochs-like breeds, “breeding-back” results were not included. It is very difficult to score “breeding-back” results as they are not as homogeneous as traditional breeds. For example, the horn size of Heck cattle varies greatly between individuals, herds and lineages. Averaging the traits found in the “breeding-back” results each would not account for the variability found within them. What can be done is scoring single individuals of “breeding-back” breeds/populations, but that leaves a lot of room for bias. One can take the best or the worst individual, or trying to figure out which individual might be representative of what is average for the breed, but that is very difficult and would, again, not account for the variability in the populations. 

All in all, I think trying to systematically objectively quantify the aurochs-likeness of cattle can only provide a very rough impression that is not any more useful than just looking at the cattle and comparing them.