10 years Breeding-back Blog + the Gramsbergen aurochs

Since May this year, I have been running the Breeding-back blog for ten years now. So far, it had more than 1,2 million page views, 500 posts and more than 2000 comments. I am very happy with that and want to celebrate it by presenting my recently finished aurochs clay model, based on the Gramsbergen aurochs. 

 

What I call the Gramsbergen aurochs is a specimen that is known only from a skull fragment with horn cores that is on display at the Museum of Gramsbergen. I know two photos of this skull fragment, that are unfortunately not online anymore. One shows it in frontal view, one in dorsal view. What is interesting is that the lateral horn orientation of that specimen is comparably vertical, around 45° in frontal view. It is very hard to tell if the skull fragment is from a bull or a cow, but since the orbital bosses are not much protruding, the postorbital region does not look very massive and the horn shape does not resemble most of the definite bull skulls, I assume it is more likely that this fragment belonged to a cow. 

For my model, I used the Sassenberg skeleton as a reference for the cranial and postcranial morphology since it is the only complete definite cow skeleton from Europe that I am aware of. As always, the model was done taking measurements from the photos that I have access to, to ensure maximum accuracy. 

For the colour, I chose a rather standard scheme out of the many possible shades that an aurochs cow might have displayed. Some depictions in Lascaux show exactly that colour. 

The head itself resembles that of Sayaguesa and Lidia cows or a mix of both. I would imagine that a combination of Sayaguesa, Lidia, Watussi and Maronesa could result in an animal that resembles this particular individual quite closely at least concerning head, horns and colour. Morphology is more difficult to achieve. 

 

Post #500: How to speed up "breeding-back"

Selective breeding with domestic cattle cannot, under any circumstances, revive the aurochs. What can be achieved is what I call the greatest similarity to the aurochs that is achievable using domestic cattle. I prefer to speak of reaching that instead of having “bred-back” the aurochs or having “completed” breeding back (a process that is actually never completed). The animals will remain domestic cattle, but with a high degree of morphological/phenotypical similarity and ecologic equivalence to the aurochs and with very similar if not identical social behaviour patterns. Some domestic traits, such as a reduced brain volume or sexual dimorphism, or a not quite as athletic bodily morphology et cetera will remain, but an identical colour scheme with a well-marked sexual dichromatism (which is not the same but part of the overall sexual dimorphism), the same body size range, a very similar if not identical horn shape and size, aurochs-like proportions, a well-expressed hump, an at least roughly similar skull shape and of course the ecologic and behavioural similarities can be achieved by breeding with domestic cattle. These cattle would be the prime option for replacing the aurochs ecologically in the wilderness. 

As readers of my blog will know, breeding for the greatest achievable similarity to the aurochs is a long-term endeavour. That is because cattle are a comparably slowly reproducing species (nine months of gestation, roughly two years until sexual maturity, litter size of only one individual) and most breeding projects do not want to sacrifice genetic diversity by using a high degree of inbreeding (which would speed up the process but has its downsides to health and adaptability). How could this long-term process be sped up? 

Concerning the greatest achievable similarity to the aurochs, there are many ways to the goal. Many combinations of cattle breeds might deliver all the desired traits (morphologically as much as ecologically), several projects are running at the moment and one can always start from scratch. But is there a most efficient breed combination, one that includes all desired traits but has the least amount of undesired traits? How to breed more efficiently than the current breeding methods employed by the projects that are running at the moment? I see three possible scenarios: 

 

-) Starting from anew with the most efficient breed combination. I have been puzzling about what might be the most efficient breed combination, and I think it would be a set of five breeds: Lidia (body morphology, sometimes also horn shape, pelage/forelocks), Chianina (body size, sometimes horn orientation and shape and sometimes leg length and morphology), Maronesa (perfect wildtype colour, sexual dichromatism, useful elements of horn curvature), Watussi (horn volume), indicine breed like Deoni (very short trunk and long legs, very small udder). The most efficient breeding scheme would be to start with a herd of Chianina cows that are covered by a good Maronesa bull, and producing a herd of F2 of that combination, and parallel to that a F2 of Lidia x Watussi and Lidia x Deoni. Ideally, there would be three lineages: one that is large, has the right colour + dichromatism, aurochs-like horn curvature and a good morphology; one that has the Lidia-like morphology with an aurochs-like horn volume and possibly shape; and one that has the Lidia-like morphology with a very short trunk and long legs. In the next step (third generation), I would create F3 of the Maronesa-Chianina lineage to stabilize the good traits plus F1 of the Lidia-Watussi and Lidia-Deoni F2. F1 will not be stable in inheritance, so creating an F2 from this new combination would be required, and only the resulting F2 with a Lidia-like morphology, short trunk and long legs, and aurochs-like horn volume with a curvature that is useful should be kept for further breeding. These F2 should then be bred to the F3s of the Maronesa-Chianina lineage, and the resulting F1 should be used to create F2 of that combination. If some of the F2s of this combination has all the desired traits, they can be used for further breeding with less strict selection. 

Minimum generations required: 6 generations (roughly 15-20 years)

Advantages: the result could be very aurochs-like 

Disadvantages: requires a large number of parental individuals to avoid too much inbreeding and relying too much on luck. Deoni would probably have to be imported from Asia, which might be impossible for practical reasons. 

 

-) Strong selection within the most aurochs-like currently available “breeding-back” population. The most aurochs-like currently available “breeding-back” population would be, in my opinion, the Lippeaue Taurus cattle population. What is lacking, to a certain degree, is horn volume and short trunk length (the latter is a problem that most taurine cattle have). Because of that, an ideal combination would be a herd of large Lippeaue cows (like Bionade, Larissa, Linea) plus a Watussi-influenced bull from Hortobagyi or from the Auerrind project that has a truly large horn volume. The resulting F1 offspring from this combination would then be selected – as the P generation is less genetically homogeneous than purebred P, the resulting F1 would not be homogeneous either, so selection is necessary. With the good F1, F2 would be created and so forth, and the animals of each generation are selected and only those that are as good or better than their parents are used for continuing the breeding. 

Minimum generations required: Indeterminable, as it depends on how good the Fs from the respective generations are, which in turn depends on luck and the number of animals used. 

Advantages: Would be the least effortful variant as it would be based solely on cattle that are already used in the project or projects. 

Disadvantages: Using current “breeding-back” cattle only might go at the expense of certain traits, mainly short trunk length. A suitable indicine breed like Deoni might have to be crossed-in, what will require more generations.  

 

-) Using introgression from wild yaks and Java banteng on an already aurochs-like population. Wild yaks would add perfectly aurochs-like horns which are found only very rarely in domestic cattle, very large size (up to 205cm withers height in bulls), long snouts, large hump, cold tolerance and physiological fitness. Java banteng would add a well-marked sexual dichromatism that is very rare in domestic cattle, large body size (up 190 cm withers height in bulls) with a well-marked size dimorphism and a short trunk. So both species would help to achieve an aurochs-like extent in aurochs traits that are rarely found in domestic cattle. I would start with two herds of Lippeaue Taurus cows, which are suitable for two reasons: a) they are the most aurochs-like “breeding-back” cattle to date, b) their comparably large body size should lead to no problems during gestation and calving. I would inseminate one herd with wild yak semen, and one herd with Java banteng semen. Of the resulting hybrids, the males would be infertile. For the herds with the hybrid cows, good Taurus bulls would be chosen. The resulting backcrosses would be selected: those that have the desired traits added by Java banteng and wild yak would be kept for further breeding, those that do not would not. The B1 individuals would be backcrossed with the Taurus bulls once again. The resulting B2 would be selected like the B1 generation. The B2 bull with the most desirable (= the desired traits added by Java banteng/wild yak present, as few as possible other traits added by these species present) would be chosen as sire for the good B1 and B2 cows. The resulting fourth-generation animals would be selected after the same principle. The best (= those that have the least influence from wild yak and Java banteng but still have the desired traits) of these two lineages would be kept for further breeding. The fifth generation animals would be F1 from the banteng lineage x wild yak lineage. As you can guess by now, F2 from this combination would be created. Only those that have the desired traits added by banteng and yak, respectively, would be kept for further breeding. They can be backcrossed with Taurus endlessly to wash out the undesired influence from the two species, as long as those individuals that have the desired traits added by them are kept for further breeding. The result would be very aurochs-like in having “perfect” horns, being very large (possibly larger than un-hybridized “breeding-back” cattle) and a more well-marked dichromatism than would be possible without hybridization. Also, they would have long snout as in the aurochs and a well-developed hump, possibly more so than “breeding-back” cattle without hybridization. 

Minimum generations required: 6 to theoretically endless (20 years to endless) 

Advantages: some important traits might be achieved better and faster than without the hybridization from wild yak and Java banteng, that is body size, hump size, udder size (or lack thereof), snout length, horn curvature and sexual dimorphism. 

Disadvantages: the hybridization with another species is controversial, some of the traits added by them are invisible or behavioural but have an impact and can only be bred out by a practice of backcrossing and selecting as much as possible, which requires several generations at least. 

 

As you see, none of these methods is entirely unproblematic, and none is noticeably faster than the other. Does this mean we would have to wait at least for another 20 years until we see a “complete” result in “breeding-back”, an individual that has all the desired and achievable traits? Probably. Some individuals, like a 25% yak or banteng individual, or a 25% Watussi 75% Lippeaue Taurus might look quite satisfying in a much nearer future already, although they would be imperfect from the breeding perspective (not genetically stable yet, too many behavioural, morphological and ecological traits from the hybrid parents, lacking some traits et cetera). Highly ambitious “breeding-back” with cattle simply takes a while. However, to be honest, I think that some herds, like the Lippeaue herd (perhaps combined with Auerrind or Hungarian Taurus cattle for horn volume), are already aurochs-like enough to be released in the wild, basically in a dedomestication experiment (that is, releasing the cattle in a reserve and not interfere with the natural breeding of the cattle) and let natural selection do the rest while the cattle are doing their ecologic job in a rewilding area. It must be noted, however, that the dedomestication process takes even longer than artificial selection. Having made this list, I think that using small and wise doses of hybridization with wild yaks and Java banteng is the most tempting of the three scenarios, as it would result in the most impressing and perhaps most aurochs-like cattle. An upcoming post is going to examine if using hybridization is a crazy idea. 

 

Did the African aurochs die out because of aridification?

It is well-known that the aurochs was wiped out by humans. It was mainly a combination of hunting, competition for habitat and competition with livestock that caused the extinction of this wild bovine. This goes for the wildtype as a whole, but it does not rule out that single populations or subspecies died out because of “natural” (i.e. non-anthropogenic) causes. This was, for example, the case with the Sicilian dwarf aurochs, Bos primigenius siciliae, which likely was outcompeted by the large mainland form when a land bridge between the mainland and the island formed at the last glacial maximum. For the African aurochs, Bos primigenius mauretanicus, there are not many works that cover possible extinction causes for this form specifically. However, there is at least one, which is Faith 2013 [1]. This work attributes the extinction of the aurochs in Africa to an aridification of its environment in North Africa around 6kya. How plausible is this? 

This idea sounds plausible for three reasons: 1) the Holocene was anything but climatically stable, and during the Atlantic period there was the so-called Holocene Climatic Optimum, during which it was warmer than today and even the Fertile crescent aridificated [2], 2) the aurochs was an animal that preferred wetter habitats and did not inhabit steppe, semi-deserts or deserts, thus an aridification could have been harmful, 3) the Mediterranean see would have hindered the aurochs from migrating northwards to less arid and more humid regions. 

There is, however, a significant problem with the idea that aridification caused the aurochs to disappear in Africa: the African aurochs did not disappear at 6kya. Bone findings suggest that the African aurochs survived at least until 1000 BC [3,4]. Furthermore, the hunting of aurochs is documented in ancient Egyptian art and hieroglyphs [3]. Less unambiguous is the mentioning of bovines with horns so large and forwards-facing that the animals had to graze backwards in Egypt by Herodotos from the 5^th century BC [4]. 

I would not be surprised if the Nile served as a refuge of the aurochs during the aridification in the Mid-Holocene, as the aurochs is dependent on wet and plane areas. After the warm and dry period during the Holocene Climatic Optimum was over, the range of the aurochs would have expanded again. But now the bovine had a competitor, humans, who competed for exactly the same habitat that the aurochs preferred. Additionally, humans hunted the bovine. So it seems that in North Africa exactly the same happened as in Europe and elsewhere, the aurochs simply had no chance in competing with humans for the same habitat additionally to being hunted. The aridification as a result of the changing climate during the Mid-Holocene cannot be blamed for the extinction of the African aurochs. 

 

References

 

[1] Faith, J.T.: Late Pleistocene and Holocene mammal extinctions on continental Africa. 2013.

[2] Vinos, J.: Climate of the past, present and future: A scientific debate, 2^nd ed. 2022.

[3] Beierkuhnlein, C.: Bos primigenius in Ancient Egyptian art – historical evidence for the continuity of occurrence and ecology of an extinct key species. 2015. 

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

 

New Auerrind breeding herd has been assembled

A few days ago, the Freilichtmuseum Lauresham has published a video and announced on facebook that a new herd of the Auerrind project has been assembled in the Wistinghauser Senne in North-Rhine Westphalia. 

The video shows three cows and one young bull. I suspect that the bull is one of the two (Sayaguesa x Chianina) x (Sayaguesa x Watussi) bulls EDIT: It is the (Sayaguesa x Grey) x (Sayaguesa x Watussi) and the cows are most certainly Maremmana x Sayaguesa EDIT: Plus one Tauros cattle cows. That means the offspring will be both parentally and maternally a cross, which is good because that is where the real breeding starts. The offspring will have much Sayaguesa influence, which is good as well, plus, with luck, genes for large and long horns (Watussi and Maremmana), maybe the little bit Chianina will also help to achieve a large size. The young bull resembles his father Alvarez (Sayaguesa x Watussi) in the video. I am looking forward to see what his horns are going to be like as much as his final body size. 

Reconstruction model of the Indian aurochs

After I finished my reconstruction of the Sassenberg bull, I now can present another model, this time of the Indian aurochs. 

In the lack of a complete skeleton or an assessment of the known material, this necessarily involved more speculations than the reconstruction of the well-known European subspecies. It is based on several incomplete crania of presumably male specimen, mainly on two skulls which can be seen here. They are not complete, but some morphological differences to the European form can be derived from it. More speculative was the postcranial body, where I simply took the skeleton of the Store-damme aurochs as the base. Not out of carelessness, but because I assume there were no noticeable differences in proportions and overall body shape between the European and the other aurochs subspecies because all of those traits were functional (the short trunk, the long legs, the presence of high spinal processes in the shoulder area forming a hump etc.). The horns are based entirely on the skull displayed in the Geological survey of India, because there are photos in frontal view and from the side of it, giving a good idea of how the horn cores look like in real. The colour is almost entirely speculative. What is likely is that the Indian aurochs had the E+ allele on the Extension locus, and that there was sexual dichromatism to at least some degree. This is the result:

 

For the colour, I used Deshi zebu bulls as a template. Those light areas between the legs are speculative, but not entirely baseless as it could also have been present in the African aurochs and even banteng have lightly coloured “armpits”. Should there ever be evidence against those light areas, I can easily paint over them on my model, but I doubt there ever will be. The horns look very large after adding the horn sheath to the cores, but the Indian aurochs had proportionally larger horns than the European subspecies. And some specimen quite possibly also larger horns in absolute dimensions. I gave my Indian aurochs a larger dewlap than what is likely for the European subspecies, because of thermoregulation and display function. Also the ear shape is that of zebus, because I consider it likely or at least possible that the ear shape of zebus was inherited from the Indian aurochs. This gives the model a more indicine appeal, additionally to the skull shape. All in all, I think it is a quite plausible representation for what the ancestor of zebus possibly might have looked like. 

 

Life reconstruction model of the Sassenberg bull

It has been two months since my latest post. I didn’t publish any posts in those two months because I was busy doing new aurochs models. I started models of the Sassenberg bull, an Indian aurochs, and the Gramsbergen skull fragment. And last week I finished my model of the Sassenberg bull. 

 

As usual, I started the model by working directly with photos of the original bones/skeletal mounts to achieve maximum accuracy. I know photos of the Sassenberg bull skeleton in lateral view, but the postcranial skeleton of this specimen is partly a composite, and thus not the most reliable options when we have more complete skeletons of a single individual. Therefore, I chose the Store-damme bull skeleton as the basis for the postcranial skeleton. I used a photo from the internet which shows the skeleton in a perfectly lateral view, and “corrected” the inaccurate posture of the mount using GIMP. I manipulated the position of the skeletal elements until an accurately assembled skeleton was the result. Using a different bull for the postcranial body is not a big issue, as there was little to no variation in the postcranial proportions of the aurochs, except for the fact that some had longer spinal processes in the shoulder region than others, but not to a huge extent. For the anatomy of the skull/head, I used a photo of the Sassenberg bull. The most idiosyncratic part of an aurochs were its horns, and I used photos from several different angles in order to correctly replicate the horn cores. Then, after sculpting the body, I sculpted the horn sheath on the horn core. This is necessarily only an approximation, as there was no general rule how much the horn sheaths added to the length and thickness of the horn. For the body morphology, I did not use more or less strongly domesticated cattle breeds as an analogue, but chose Spanish fighting cattle individuals as much as living wild bovines. I did so because the morphology of cattle was greatly affected by domestication, and Lidia cattle are probably the least-derived taurine cattle breed. But there is always some variation concerning the bulkiness of the individual, and it also depends on the individual age. A very old bull, be it Lidia or a wild bovine, is certainly more massive than a very young adult bull. I wanted to reconstruct the Sassenberg bull in its “prime time”, perhaps at the age of around 6 to 7 years in domestic cattle age years. I will do more massive “old” bulls in the future as well. 

This is the result: 

The model was sculpted from air-drying modelling clay of the DAS brand and was painted with acrylics. It is 33 cm tall at the withers, the scale to an actual aurochs bull depends on which height you choose for that, as the European aurochs varied from 160 to 200 and perhaps more cm at the withers in life. During sculpting my model, I constantly checked its accuracy by superimposing a photo of the model on the “corrected” photo of the actual skeletal mount, and I can happily say that the model lines up perfectly with the skeleton in lateral view. As for the head and horns, here is a photo of the model next to a photo of the Sassenberg mount in exactly the same position: 

I am very happy with the result and I think it is quite likely that the model is more or less accurate. More reconstruction models are about to follow, the next one will probably be the Indian aurochs. 

 

Is outbreeding the wisent necessary?

I did a couple of posts where I suggested cautious outbreeding for the wisent using its closest living relative, the American bison, in order to overcome a supposed inbreeding depression resulting from the extreme genetic bottleneck of the modern population (which descends from only 12 founding individuals). See 

- Over-purity as a danger for the wisent?

- What to do with the wisent in the Caucasus?

- Controlled hybridization for saving the wisent? 

Consequently, I used to regard the Caucasus population, which has been living in the wild for several decades now and has an American introgression of roughly 5%, as very valuable for the conservation of the species. It has been several years since I wrote these posts, and which this one, I want to give my current take-on to the question if outbreeding the wisent is actually necessary for its conservation. 

This question is sometimes intermingled with the controversy revolving its taxonomical status in relation to the American species. Some consider both forms subspecies of the same species because they are fully interfertile, i.e. they can produce hybrids that are fertile in both sexes, others prefer to retain the separate species status for both forms. I have no firm opinion on this, because I think having one is not useful as there is a) no clear definition of a species that works universally and that everyone agrees on and b) it is only intuitive that not all species are differentiated to the same extent because the time of separation between two given lineages may differ, the intensity of the selective pressure the lineages may experience may differ, the impact of mutations that appear in those lineages may differ (one mutation that has a drastic effect may prevent hybridization in otherwise very closely related lineages). Thus, I think having a firm opinion on if European and American bison are two distinct species or subspecies of one species and fighting over it is not very useful. Furthermore, moving back to the actual topic of this post, it is not really relevant for the question if American introgression should be utilized in the conservation of the wisent, as the taxonomical status of both forms does not make both lineages any more similar or dissimilar to each other. Taxonomy describes facts and does not create facts. 

In my posts linked above I describe detrimental consequences of inbreeding that can be found in the wisent. The fact that these consequences exist, however, does not tell us much about the frequency at which they appear and if they are a problem for the long-term wellbeing of the species. The status survey and conservation action plan for the wisent from 2004 describes the inbreeding depression in the wisent as “very small” [1]. Tokarska et al., who evaluate the genetic variability in the Bialowieza herd, even note the “absence of any signs of inbreeding depression”, although the low genetic diversity is seen as a potential threat as it implies low adaptability [2]. 

It is true that wisent populations may suffer from wisent-specific balanoposthitis and the species is particularly sensitive to foot and mouth disease, and introgression from American bison might (or might not) help to overcome this (although American bison are not immune to the latter disease either), but the average percentage of males in Bialowieza that have had balanoposthitis from 1980 to 2005 was only 6,5%, rarely reaching above 10% in some years [3]. 

What the wisent really needs in order to ensure the long-term prosperity of the species would be space for large populations (several thousands) to thrive and – very important – protection from poaching [1]. Larger populations, even if inbred, have a much higher chance of surviving than small, dispersed herds of only a few dozen individuals. If the population is large enough (the wisent conservation action plan from 2004 suggests numbers of up to 3000 individuals), the individuals that display negative consequences from inbreeding because they have a higher number of deleterious alleles would have less reproductive success than those that have fewer deleterious alleles. Eventually, natural selection in a population that only is large enough will lead to a relative increase of non-deleterious alleles and a decrease or even disappearance of deleterious alleles. 

A scenario in which outbreeding with their American relative would be beneficial is when there is a gene at which all or many wisents are homozygous for a deleterious allele that has a noticeably detrimental effect on the organism, and American bison have healthy alleles on this very gene, or if there were even several of such genes in which this is the case. In this scenario, it would certainly be beneficial to use American introgression in a separate studbook and using genetic tests in order to ensure that the hybrids only carry the healthy alleles on the gene(s) in question. But no such scenario has been reported yet. That means that further research on the genetic health of the wisent is necessary to determine if outbreeding would be useful and worth the effort at all, and it is perhaps questionable if that was the case if there was enough space for large populations of wisents to thrive. We should not forget that both bison types are the result of unique evolutionary processes on different continents, and full transparency in the form of a separate studbook would be a prerequisite for carrying out introgression. 

What to do with the Caucasus population that has roughly 5% of American introgression, then? I still think it is a very valuable population, for the very fact that several decades of natural selection followed the hybridization event in the 20^th century. The genetic and phenotypic health of this population should be studied. For example, it should be examined if balanoposthitis is less frequent or even occurs at all in the Caucasus population. I think this population should be studied, and not exterminated, as suggested in the wisent conservation action plan from 2004 – considering that there is no continuous range that includes herds without American introgression the danger of contaminating the purity of other herds is low. And even if the herd merges with a pure herd, only the alleles advantageous for the survival of the population in that specific environment get to spread – there cannot be anything bad about that, from an evolutionary perspective. The original wisent form that was native there, B. bonasus caucasicus, has been hunted to extinction already anyway. Arguments that the wisents with American introgression are detrimental to the ecosystem or maladapted are very dubious, as I explain in the post “What to do with the wisent in the Caucasus?” linked above. 

 

All in all, I think that trying to establish large (several thousand individuals) populations of the wisent in the wild that are protected from poaching should have priority over the idea of outbreeding in order to conserve this species in the long run. If one wants to execute outbreeding, more research on the genetic health of the wisent should be done before that, in order to see if it will be effective in the first place. Studying the Caucasus population that already has American introgression would be relevant for this. 

 

Literature

 

[1] Pucek, Krasinski, Krasinska, Olech, Belousova: European bison – status survey and conservation action plan. 2004. 

[2] Tokarska et al.: Genetic variability in the European bison (Bison bonasus) population from Bialowieza forest over 50 years. 2009. 

[3] Krasinski & Krasinska: Der Wisent – Bison bonasus. Neue Brehm-Bücherei. 2008. 

 

 

Portrait of a generic aurochs cow

For today, I have a quick little sketch of an aurochs cow that I painted with GIMP. It is not a reconstruction of a particular specimen, but is a portrait of a generic aurochs cow that aims to show all the traits typical for female European aurochs. 

So far, no "breeding-back" cow of any project looks like that. However, I think it is quite possible to achieve something that resembles this quite closely. Possible breed combinations suitable for this endeavour would be Sayaguesa, Lidia, Chianina/Maltese, Watussi and Maronesa, considering only the best representatives of the respective breeds. One has to keep in mind that "breeding-back" with cattle is a long-term project as they are a slowly reproducing species. A possible breeding scheme could be breeding an F2 of the combination F2 (Sayaguesa x (F2 Lidia x Chianina/Maltese)) x F2 (Sayaguesa (F2 Watussi x Maronesa)). That would take five generations, hence 10-15 years. That is a long time of course, but current breeding projects have been running for a similar time span for now and the results of such a lineage could be quite qualitative. It must be kept in mind that the scheme I just described is only one of very many ways of getting to the goal that is producing a lineage of cattle that resembles the European aurochs to the largest possible degree. 

What a "breeding-back" zebu could look like

All current “breeding-back” projects focus on the European subspecies, but that one is not the only that left living, domesticated descendants. There probably was introgression into African taurine cattle from B. primigenius mauretanicus, and the Indian aurochs was domesticated as well, the results being called zebus. A “breeding-back” initiative for zebus would be very interesting, as they still exhibit some of the autapomorphies of the Indian aurochs. 

However, since the Indian aurochs, also called Narbada ox or as I also like to call it, wild zebu, is less well-documented than the European form, the breeding objectives for such a zebu “breeding-back” project would be less clear. I did a number of posts on the Indian aurochs, the most recent being this one. 

To sum up what the Indian aurochs most likely roughly looked like: 

- smaller than the European form, possibly between 150 and 160 cm withers height in bulls

- proportionally larger, slightly more upright and more wide-ranging horns 

- narrower skull with less prominent eye sockets 

- probably very similar postcranial anatomy, with long legs, short trunk and a shoulder hump (not to be confused with the fleshy indicine hump) 

- perhaps a slightly larger dewlap than the European aurochs 

- a colour possibly similar to that of the European aurochs, perhaps with some minor differences as zebu colours suggest

- very likely sexual dichromatism comparable to the European aurochs and Java banteng 

All of these traits can be achieved or approximated by breeding with less-derived zebu landraces. I would include: 

- some Deshi variants (wildtype colour, useful anatomy) 

- Kankrej (sometimes horns of a useful curvature and size, large-bodied) 

- Deoni (very short trunk and long legs, small udder and slender body) 

- Watussi (horn size and partly curvature)

This set of breeds can result in a zebu that looks more like what their wild ancestor looked like than many or all other zebus breeds. However, it would not yet seize the complete potential to mimic Bos primigenius namadicus as the horns would probably be more or less too upright, the zebus would still have an indicine hump which is unlikely to have been present in the Indian aurochs, they would have little to no sexual dichromatism as this trait is barely present in zebus. The solution to that is, in my opinion, to include: 

- Sayaguesa: for the overall aurochs-like morphology, for the lack of an indicine hump and the presence of a well-developed shoulder hump as in the aurochs 

- Java banteng: for the sexual dichromatism. Many cow-coloured zebus have a colour that is virtually identical to that of the Java banteng minus the white socks and buttocks (reddish-brown colour, dark brown dorsal stripe etc.), suggesting that female Indian aurochs had this colour. Of course it would be possible to include a taurine breed that reliably has sexual dichromatism such as Maronesa, but in these the cows are not nearly as lightly-coloured as in zebus and Java banteng. 

Some might think now that I am crazy suggesting a taurine breed and another species for “breeding-back” focusing on the Indian aurochs. But for once, I am not afraid of using less-derived zebu landraces for “breeding-back” focusing on the European aurochs, since they share some alleles with the European aurochs that taurine cattle have lost and contribute some phenotypically desired traits that taurine cattle do not have. So the reverse is legitimate to me as well, using a taurine landrace to acquire a trait that cannot be achieved with zebus alone, in this case, the lack of an indicine hump and the overall aurochs-like morphology. As for the banteng, I suggest using wild yaks and Java banteng for “breeding-back” focusing on the European subspecies, but only in very small doses and only in experimental herds, used very wisely with efficient selection (and not rampant hybridization in order to see what happens). The wild yak is unnecessary for a zebu project and possibly even counterproductive considering its climatic adaptions, so I’d only go with small doses of Java banteng to breed for the right colour dimorphism. I would backcross the hybrids as often as possible with “pure” zebus until the taurine and banteng influence is reduced to virtually nil genealogically, but always keeping those individuals that display the desired traits. 

I did a painting with GIMP what such a “breeding-back” zebu bull could look like, and this is the result: 

Overall, while the result would still be a domestic animal, it possibly resembles what we know of the Indian aurochs quite well on certain traits, and would be suitable to fill its ecologic niche in Southern Asia. 

 

 

 

 

Is the domestication syndrome a myth?

In most if not all of my posts on domestication and dedomestication I mentioned the concept of the domestication syndrome that says that domestication works by the same mechanisms and has the same effects in any species that was domesticated. Domestic animals share certain traits, which are that eye-catching that it seems very intuitive that the domestication syndrome as such exists. Parts of my dedomestication hypothesis are based on the assumption that there is a domestication syndrome. However, the concept has been called into question in several works. 

The domestication syndrome is the assumption that all domestic animals, mammals in particular, share certain phenotypic traits, both behavioural and morphological. These include paedomorphy in behaviour and morphology, a reduced brain volume, reduced sexual dimorphism, piebald or spotted coat colour patterns, loss of seasonal adaptions, increased reproductive rate, earlier maturity and others. The hypothesis was expanded in publications discussing the findings of the famous Farm fox experiment, namely that artificial selection on tameness alone produced many of the typically domestic traits as a by-product, suggesting that there is a connecting mechanism working during domestication. You can read my post that I linked above for more detail and literature references on that. 

 

The validity of the Farm fox experiment as evidence for the domestication syndrome is called into question in some sources. For example, the alleged cranial shortening in the foxes selected on tameness is based on anecdotical evidence, it turned out that they are not distinguishable from wild foxes in cranial morphology [1]. A brain volume reduction has not been detected in selected foxes [1]. White spotting in the colour that has been said to be a by-product of the selection on tameness is also found in the control group and the foxes selected on increased aggression [2]. However, the white spotting is more common in the foxes selected on tameness than in the other groups [1]. Nevertheless, a spotted coat colour and a curved tail (the latter trait found in 10% of the foxes selected on tameness), is not associated with increased tameness in the individuals [1]. Lord et al. state that due to the limited population size of the starting population, it is possible that shifts in allele frequency were caused by “chance alone” [1], therefore morphological changes in the selected foxes do not necessarily have to be caused by selection on tameness according to the authors [1]. 

However, there seems to be a weak correlation between tame behaviour and white spotted coat colours in rats and foxes [3]. It has been found, interestingly, that there is no correlation between several physical characters considered symptoms of the domestication syndrome (f.e. floppy ears, spotted coat colours) among each other, and with behaviour among dogs [4]. This seems to be contradictory to what would be expected by a very strict application of the domestication syndrome hypothesis. Also, mutations causing piebald coat colour patterns also appear in wild animals. It is not all that rare in several deer species, for example moose in North America: 

If the piebald coat colour patterns in domestic animals are strongly connected to tameness, it would have to be expected that these moose are also less fearful towards humans than their “normally” coloured conspecifics. This assumption would have to be tested. 

There is a paper by Lord et al. that calls brain volume reduction as a consequence of domestication into question [5]. However, the reduction of brain volume is well-documented for many domesticated species [6], and has recently also been found to be the case in cattle compared to the aurochs [7]. Another problem is that the paper by Lord et al. adopts the premature conclusion by Gaunitz et al. 2018 that the Przewalski’s horse is feral and “not wild in any sense” [6], while they consider the feral European mouflon a wild animal to compare sheep against [6]. So they consider a wild animal feral and a feral animal wild, what is a bit of a problem in the argumentation. 

A major component of the hypothesis that selection on behaviour results in alterations of physical appearance is the proposal that neural crest cell genes are affected by selection on tameness [2,8]. The neural crest is a precursor of many cell types in vertebrates, pigment cells among them. The hypothesis says that if the genes of neural crest cells are affected by selection on tameness, the migration of the precursors of pigment cells is distorted, causing irregular unpigmented areas on the body, resulting in the piebald coat colour that is seen in many domestic animals. A very recent paper compared neural crest genes of domestic animals of several species and compared it to the respective wildtypes or animals related to the wildtype (bison were used to compare with domestic cattle, for example). The result was that evidence for positive selection on neural crest genes was found in nearly all cases [8], providing support for the hypothesis that alterations of the genes of the neural crest played a role in domestication of the species that have been domesticated [8]. Interestingly, in the Farm fox experiment it was noted that crossing two white-marked foxes would occasionally produce offspring that held their head askew [1]. I think it is possible that the allele(s) producing these white markings are connected to factors detrimental for the development of the nervous system, what would support the neural crest hypothesis, although other explanations are plausible as well (f.e. asymmetric development of musculature, abnormities in the vestibular system) – that phenomenon deserves further investigation in my opinion. 

Domestication goes hand in hand with an increase of deleterious alleles as a result of mutation accumulation since natural selection plays no or only a minor role in domesticates. This phenomenon is described as the “costs of domestication” [9]. Mutation accumulation might be an alternative explanation for why piebald coat colour patterns are found in all domesticated species. Rather than being connected to behavioural aspects that get selected for during domestication, it is possible that these piebald patterns showed up due to spontaneous mutations that also appear in wild populations, and humans tended to favour these deviant colour variants in their breeding regime. In fact, piebald patterns are only one type of novel colours that appear in domestic populations. Many domesticated species show melanism (found in cattle, dogs, horses, cats and others), erythricism, leucism and albinism as much as completely novel coat colours, yet nobody suggested that these pigment modifications are a common consequence of domestication and possibly connected to behavioural traits (with the exception of melanism, which has been linked to increased aggression in the past). Piebald patterns even exist in “domesticated” fish such as the goldfish, and as far as I know goldfish were never particularly selected for tameness. The fact that white markings are more common in the foxes selected on tameness than in the other lineages can also be due to genetic drift or the loci regulating those markings being coincidentally genetically linked with those regulating tameness on the same chromosome. Therefore, white spots do not necessarily have to be a consequence of behavioural modifications during domestication.

While white spotted patterns are not a good example for the connection between physical characteristics and behaviour and the role of this possible connection in domestication, I would not give up that hypothesis. We should not forget that paedomorphy and a reduced brain volume are very common among domestic animals, and that changes in hormone productions likely played a role in domestication. Thyroid hormones have a major role in postnatal growth, pigmentation, brain development, adrenal gland function and development of the gonads [10]. Selection on tameness is, to a certain degree, selection on paedomorphic behaviour as the fear response of juvenile mammals is much less intense than that of fully grown ones. Therefore, selection on tameness might have influenced the overall development, causing the expression of hormones relevant in adulthood to be delayed. This would lead to an overall paedomorphy because it would affect thyroid hormones, among others (corticosteroids might play a role as well). If the consequence is a shortage in thyroid production, this would have a dramatic influence on the morphology of the animals. For example, hypothyroidic rats are smaller, have a shorter snout and floppy ears – they have paedomorphic, domestic characters. Hypothyroidism is also known to cause cretinism in humans, which includes symptoms such as shortened extremities, reduced body size and lowered cognitive abilities. This is what we see in many domestic animals. I also think that hormonal changes are responsible for the brain volume reduction, perhaps even the thyroid hormones, rather than the fact that a domestic life is less cognitively demanding than a life in the wild, what is usually offered as explanation for the smaller brains of domesticates. We should also not forget that the neural crest genes of domesticates show signs of positive selection as outlined above, although pleiotropic effects leading to a change in physical appearance have not been proven directly yet. 

I think the domestication syndrome concept would be invalidated if there was a domesticated species that is completely devoid of any traits that are considered symptoms of the domestication syndrome such as paedomorphy, reduced brain volume and others, yet still behaves completely domestic, i.e. has a very moderate fear response, reduced aggression and increased tameness compared to its wildtype, trainability and agreeableness. Sixteen mammal species have been domesticated, yet there is no such case. This indicates to me that the domestication syndrome is a valid concept, although piebald colour patterns possibly have to be excluded from the list of symptoms considering the weak to absent correlation between them and tameness. 

 

Literature

 

[1] Lord et al.: The history of Farm foxes undermines the animal domestication syndrome. 2019. 

[2] Wilkins: A striking example of developmental bias in an evolutionary process: the “domestication syndrome”. 2019 

[3] Wilkins et al.: The “domestication syndrome” in mammals: A unified explanation based on neural crest cell behaviour and genetics. 2014

[4] Wheat et al.: Morphology does not covary with predicted behavioral correlations of the domestication syndrome in dogs. 2020. 

[5] Lord et al.: Brain size does not rescue domestication syndrome. 2020. 

[6] Balcarcel et al.: The mammalian brain under domestication: discovering patterns after a century of old and new analyses. 2021. 

[7] Balcarcel et al.: Intensive human contact correlates with smaller brains: differential brain size reduction in cattle types. 2021. 

[8] Rubio: Neural crest cell genes and the domestication syndrome: A comparative analysis of selection. 2022. 

[9] Moyers et al: Genetic costs of domestication and improvement. 2017. 

[10] Dobney & Larson: Genetics and animal domestication: new windows on an elusive process. 2005

Extinct megafauna that could be revived using genome editing

Humans wiped out countless species of animals. Some of those species, particularly those that died out comparably recently, might actually be retrievable. Usually, cloning comes to mind when talking about reviving extinct animals. However, somatic nucleus transfer for reproductive cloning requires an intact cell and not just the DNA of the animal, which is why it is not available for most species wiped out by man. However, there are a few megafaunal species that have been wiped off from which we have at least one and in some cases several complete genomes. If there is a still extant species that is closely related and would make a suitable surrogate, it would be possible to exchange the alleles specific for species A with those for species B and thus creating a viable cell with the genome of the extinct species in question with genome editing. This limits the number of extinct animals that could be revived. For example, I would imagine it to be pretty difficult if not impossible for a species like the thylacine, which has been evolutionary separated for 30 million years from its closest living relatives. In some cases, it could be easy and much less effortful because of the lower number of genes that differ and the suitability of the surrogate because the animal has a very close living relative. In this post, I present a number of megafaunal species from which full genomes either have been acquired or at least could potentially be acquired and which have a more or less closely related relative that can be used for genome editing and as a surrogate. The mitochondrial DNA of the resulting animal would be that of the donor cell, which would be from the related species. However, as mitochondrial genes are highly conserved among mammals this would not have much of an influence. Using closely related species also has the advantage that the behaviour will be rather similar, especially among the large herbivore species that I am going to list. This makes the rearing by a surrogate mother and socialization of the result less problematic or maybe not even an issue at all. 

I see reviving an extinct animal that has been wiped out by man as a contribution to species conservation just as breeding an endangered species or subspecies. One might ask, particularly in the case of wiped-out subspecies, why doing that at all if there are suitable ecological proxies. Occasionally some even question the need to conserve endangered subspecies such as the Northern White rhino because their conspecifics from other subspecies would function ecologically the same or very similar. Personally, I cannot relate to that mindset. Conservation is about preserving biodiversity and the preservation of evolutionary more or less distinct subspecies is a vital part of that. The same goes for reviving extinct species or subspecies – it would greatly increase the biodiversity again, after it has been depleted by man when the species or subspecies was wiped out. 

 

Bubal hartebeest, Alcelaphus buselaphus  

This animal is sometimes also considered a subspecies, but that question is merely taxonomical and not relevant for “de-extincting” the animal. In any case, other members of Alcelaphus could be used for genome editing and as a surrogate. Many individuals must have been preserved as trophies, and it is potentially possible to acquire full nuclear genomes from them. 

 

Bluebuck, Hippotragus leucophaeus  

Other members of Hippotragus could be used as a surrogate and for genome editing. It can be tried to acquire a fully nuclear genome from taxidermies.  

 

European aurochs, Bos primigenius primigenius

One full nuclear genome has been resolved in 2015 from a well-preserved Neolithic bone. Considering the richness of recent aurochs material, it could be possible to obtain quite a few more complete genomes. And there is a very close living relative, modern cattle. The number of genes that would have to be exchanged would probably be lower than in most of the other cases I am listing here, and also the surrogate and the procedure of implanting an embryo would be completely unproblematic. And considering the similarities in behaviour between cattle and aurochs, socialization will not be problematic either. For these reasons, I consider the aurochs one of the most realistic candidates for a revival through genome editing. Even if the resolved genome remains the only one to be fully resolved, one revived aurochs individual still can be outbred using aurochs-like cattle. I wrote a post on that a few years ago. 

 

Several types of wild horses 

There are well-preserved mummies of Siberian wild horses, Equus caballus lenensis, and one of the Yukon wild horse, Equus caballus lambei, so it could be possible to obtain fully resolved nuclear genomes from that. A domestic horse could be used for genome editing and as a surrogate. Even if only one genome can be obtained, the revived horses can be outbred with Przewalski’s horses and/or robust landraces in the same manner as I suggested for revived aurochs. 

 

Kouprey, Bos sauveli  

Numerous kouprey specimen have been preserved as trophies and one skin. It could be possible to obtain full nuclear genomes from that very recent material. The closest living relative is the Cambodian banteng which hybridized with the kouprey in the past. It can be used for genome editing, as a surrogate and even for outbreeding if necessary. 

 

Quagga, Equus quagga quagga  

The quagga is not and cannot be bred-back from extinction with living Plains zebras, which is why it would be desirable to try to acquire full genomes from the numerous preserved skins and the few skeletal material that is preserved of this zebra. The zebras of the Quagga Project can be used for genome editing, as a surrogate and outbreeding if necessary. 

 

Pyrenean ibex, Capra pyrenaica pyrenaica  

This is the only extinct animal that has been cloned so far, unfortunately the clone died shortly after birth. Genome editing with individuals from other subspecies of Capra pyrenaica could be more successful, they can be used as surrogates and for outbreeding. 

 

Steppe bison, Bos (Bison) priscus  

There are plentiful of remains from steppe bison, including soft tissue. Perhaps it would be possible to obtain full nuclear genomes from that. Needless to say, that still existing bison, be it European or American, can be used for genome editing, as a surrogate and outbreeding. 

 

? Woolly mammoth, Mammuthus primigenius  

Currently, there is no de-extinction project in the strict sense focusing on the woolly mammoth. There is the attempt to create a “mammophant” by introducing mammoth alleles for certain traits into the genome of an Asian elephant, what is not what I would consider de-extinction in the strict sense. If doing that is possible, it might also be possible even if more effortful, to exchange all alleles of genes where Asian elephant and woolly mammoth differ. However, since implanting an embryo into an elephant is very complicated, and those who want to create plan to use an artificial womb, a technique which does not exist hitherto, I wonder if it is feasible to recreate the woolly mammoth for practical reasons. 

 

Caucasian Wisent, Bos (Bison) bonasus caucasicus  

Several skins and trophies of this wiped-out subspecies (or species or variety, there is no consensus on its taxonomic status) exist, so it could be possible to obtain full nuclear genomes from it. European bison of the Lowland-Caucasus line, which partly descend from the last Caucasian wisent bull, could be used for genome editing, as a surrogate and for outbreeding. Obtaining genomes from remains of wisent prior to the bottleneck in the 20^th century could also help to greatly increase the very limited genetic diversity of this endangered bovine. 

 

Cave lion, Panthera spelaea  

Several very well-preserved pubs of this feline have been found. It might be possible to acquire full nuclear genomes from that, and the closely related actual lion would be suitable for genome editing and as a surrogate. 

 

Schomburgk’s deer, Rucervus schomburgki  

Some remains of this deer species exist, a sister species from the Rucervus clade could be used for genome editing and as a surrogate. 

 

Japanese sea lion, Zalophus japonicus

There are taxidermied specimens of this sea lion, related species of the Zalophus clade can be used for genome editing, as a surrogate and possibly outbreeding if necessary. 

 

Caribbean monk seal, Neomonachus tropicalis

There should be some remains of this recently extinct species, the related Hawaiian monk seal can be used for genome editing, as a surrogate and possibly outbreeding if necessary. 

 

One common objection against the revival of extinct animals is “one individual is not enough to build a population”. Apart from the fact that even one individual could tell us a lot about the extinct animal species/subspecies, it could be possible to get several genomes of those recently extinct species. Getting the full genome of five or ten individuals from different regions and times would probably enable to get a genetic diversity comparable to that of the modern wisent population, which descends from only twelve founding individuals from the same population. Some wisent individuals show inbreeding-related problems, but not to the extent that it threatens the survival of the species. An even more extreme example would be the Mauritius kestrel. Apart from that, related species/subspecies can always be used for outbreeding to add genetic diversity. Hybridization among related species with neighboring or overlapping distributions is very common in the animal kingdom.