Wednesday, 2 August 2017

Is it legitimate to speak of a "new aurochs"?

A problem that “breeding-back” faces is oversimplification; the Heck brothers, the creators of the idea of “breeding-back”, are guilty of it, many zoos tagging small dachshund-like Heck cattle as “recreated aurochs” as well, and after all, the term “breeding-back” is a simplification in itself because selective breeding with domestic cattle cannot revive the original aurochs (that’s why I usually write it in quotation marks). Or does it? Some claim it can, depending on definitions. After all, it is a language issue, and with this post (which I prepared already two years ago but never finished it) I am going to introduce this language issue, the arguments of the people who are looking forward to an “aurochs 2.0” and my personal opinion (maybe some of you remember my post on a similar language issue: why I think the zebras of the Quagga Project should neither be called “quagga” nor “Rau quagga”).

What do we mean by “aurochs”?

First off, we have to define what an aurochs is to see what deserves this status. The aurochs was, per definition, the wild ancestor of taurine and zebuine cattle (I don’t want to get into the discussion of taurine cattle and zebuine cattle are separate species, let us focus on taurine cattle and the Eurasian aurochs subspecies). This is the way the term “aurochs” is used in the literature, and is the definition that every zoologist is going to give you. The Eurasian aurochs was the wild, undomesticated ancestor of taurine cattle.

Basically cattle are domesticated aurochs. So far so good. There is no universal scientific consensus on whether domestic animals and their wild-types should be regarded and classified as one species or as two distinct species. Probably lumping them into one species or splitting them into separate species is more justified in some cases than others. In the case of the dog, where the true nature of its wild type is not entirely resolved and considerable cognitive, behavioural and also dietary differences to wolves exist (see here), I think it is better to tentatively regard them as a separate species, Canis familiaris. Domestic horses, on the other hand, are morphologically far less domesticated than cattle, and their behaviour under natural circumstances is virtually identical to that of wild equines, and there are no dietary or other ecologic differences to what is assumed to be its wild-type. They interbreed with Prezwalski’s horses without problems (despite differing in chromosome number) and genetic information tells us they had a lot of female wild horse introgression in Europe. Therefore, I definitely see the domestic horse as a member of Equus ferus. Whether or not such domestic, man-made populations of a species deserve an own taxonomical status in form of a subspecies or variety (f.e. Equus ferus caballus resp. Equus ferus f. caballus), is up to ones personal preferences, and I myself have no general opinion on that because it is subjective paperwork to me that does not alter the animals we are dealing with. I see zebuine as much as taurine cattle as members of Bos primigenius. What we know of the aurochs’ ecology and social behaviour is congruent to that of domestic cattle, genetic information tells us they interbred without problems (although Anton Schneeberger reported something different when he visited the last aurochs herd at the Polish forest of Jaktorow; not sure what to make of that note).

Does this mean that all cattle can be called aurochs? Basically, they are artificially modified versions of aurochs. But this name is and has always been the term for the wild animal, in both colloquial and scientific use. No serious zoologist would say something different. Nobody would call normal, domestic cattle aurochs without an extra note. And language is convention-based. You could call the aurochs “wild cattle” on the other hand, but this is ambiguous because it is also applicable for other species.
So I personally do not call any domestic cattle “aurochs”, “aurochs cattle”,  “domestic aurochs”, or anything like that (although the latter one is definitely legitimate, but simply not used).

But those who are looking forward to call the results of “breeding-back” a “new aurochs” or “aurochs 2.0” argue that if the results are close to the aurochs enough, they can be labelled as a new aurochs. Basically they go by the duck test and say: “When I see cattle that looks like the aurochs, behaves like the aurochs and grazes like the aurochs, I call it an aurochs” and that argument gets endorsed by the fact that domestic cattle descend from the aurochs and most likely share a lot of, if not all, characteristics regarding ecology and social behaviour. So basically, if you manage to breed cattle with enough phenotypic resemblance to the aurochs that is also able to survive in wilderness on its own and displays the behaviour of wild bovines, is this enough to call it a new aurochs? There would still be differences, especially regarding genetics, but those speaking of a “new aurochs” argue that neither would contemporary aurochs be identical to those from 1627 if they would have survived till today. I see some problems with that argumentation.

First of all, how much resemblance is enough? Here is where the subjectivity starts already. “Breeding-back” focuses on many traits at the same time, and uniting them truly stable and getting rid of all undesired traits would take a very long time (prepare for about a century and a lot of area size and money). Recessive traits in particular like colour dilutions and others will show up for a long period of time. Furthermore, it is probably not possible to breed a perfect morphological imitation of the wild aurochs using domestic cattle only, as outlined in this post. It will probably be impossible to achieve a population without any domestic traits, morphologically and behavioural, by selective breeding with domestic cattle alone. The cattle released in the reserves will necessarily be imperfect in this respect, especially since you have to keep up a certain amount of genetic diversity. So who decides how much imperfection to permit? There will be no universal opinion on that, because people have different preferences. Apart from that, you can bet that if one project achieves cattle with a perfect colour scheme but slightly smaller horns, and the other project cattle with perfect horns but also a number of undesired colour variants, the projects are going to use the respective imperfections of the other project to explain why their cattle is superior. And to complicate the subject even further, there is no 100% certainty about the morphology and each detail of the looks of a living European aurochs. I made a post about it, it includes aspects such as the colour of the forelocks on an aurochs bull, the colour shades possible for cows, the extent of curly hair on male aurochs and others. In the end, we have no photos or taxidermies of living wild aurochs to compare with but deduced its life appearance based on skeletons and contemporary art and literature.

So the results of “breeding-back” will necessarily be different from the original aurochs. But so would be living aurochs if they survived till today, people argue. Yes, but the difference between an aurochs from 1627 and a surviving aurochs of 2017 would be marginal compared to those between the aurochs from 1627 (or any aurochs) and living domestic cattle, no matter how morphologically similar we breed them. First of all, the time distance we talk about is not that dramatic as it sounds. 400 years are not much in the face of evolution, especially since there were no ecological changes since then that would have altered the selective pressure on the aurochs (except, of course, anthropogenic factors). How big was the difference between aurochs 40.000 years ago, and 39.600 years ago? Or 11.000 years ago and 10.600 years ago? Or 120.000 years ago and 120.400 years ago? Pretty marginal if anything of relevance. We can say that European aurochs got smaller during the Pleistocene (although there was regional variation), and also that their horns lost size (which might be due to a decline in predator fauna, which, in turn, might have an anthropogenic cause), and the last aurochs post the Middle Ages were definitely smaller and had meagre horns. This was very likely due to dramatic habitat restriction and disruption and probably also trophy hunting, therefore anthropogenic factors. My argument is: if aurochs would have had the possibilities to thrive in natural areas large enough, untouched by humans, and survived till today, there would be no noticeable differences between the aurochs of now, 1627, the antiquity, bronze age and perhaps also the beginning of the Holocene. Other European mammals did not evolve dramatically either, and in the rare cases where differences have been found, they have been linked to human activity (such as proportions and antler size of fallow deer1).

Of course genetically, the populations would not have stagnated even if the selective pressure did not change noteworthy. Genetic drift always happens, but those differences would most likely be of minor relevance (mostly neutral variations of protein sequences). But the difference between a wild type and a domestic animal is dramatic (and the results of “breeding-back” are and will be domestic animals, unless they have been living in the wild for a sufficient amount of time*). Not only are domestic animals a fractioned and mostly isolated population based on only a small founding number of wild individuals, their genetic architecture is greatly affected by domestication. Numerous genes for development, endocrinology, neurology and probably also metabolism have been altered, resulting in the gross differences in behaviour and morphology we see between wild and domestic animals (see here or here). And it is to be assumed that these genetic modifications are universal to all members of a domestic animal type, otherwise they would not display the domestic trait. This, in turn, means that the original wild type alleles on these genes have been lost. That is why the claim “the genes of the aurochs were not lost but are just split up among domestic cattle, and breeding-back is going to unite it” is only true for the morphological traits we can see in modern cattle and breed for, but not the fundamental differences between a wild and domestic animal.
The aurochs, however, was a wild animal by definition. If it is not a wild animal, it cannot be an aurochs in the strict sense of the term as it is used in zoology.

* There is no absolute measurement on how long it takes for domestic animals turn into a genuine wild animal again. I would say that a wild animal should be defined as an animal which genome is shaped and determined by nature and not man, and for that to be wholly achieved, it would take quite some time, at least dozens of generations, or even hundreds.

But let us assume that the current “breeding-back” projects one day achieve truly stable populations displaying the true maximum of aurochs-likeness that we can achieve with modern domestic cattle (which would, in theory, take a very long time), and that those populations all get released in some natural areas, and natural selection and phenotypic plasticity would slowly remove all vestiges of domestication (paedomorphy, domestic body shape etc.) and we have the desired end result. Be aware of the fact that it would take very, very long to achieve this ideal result – I am again talking about centuries. Would it be OK to call these results “new aurochs”, a post-domestic wild animal opposed to the pre-domestic “old aurochs”, when both animals share most of the morphologic, behavioural and ecological traits and belong to the same species anyway?

Let us say we find a consensus for that. What implications would it have? You have to consider what kind of impression this arbitrary synonymization leaves to experts and non-experts.
People with the necessary background knowledge might assume that the same clueless self-delusion of the Heck brothers is the case here (that led them to proclaim the revival of the aurochs after they created a very heterogeneous cattle breed that shows some resemblance in coat colour and horn shape, that is otherwise totally domestic and very instable in inheritance), or presume that you do not take it all too seriously with the facts. You might be accused of unprofessional over-simplification. I remember that a commenter on my blog wrote that gluing hair on Asiatic elephants does not bring back the woolly mammoth either, and I absolutely understand this reaction to the impression that the term “breeding-back” alone might give. 
And many would simply be unwilling to call anything else than the original predomestic wild-type of B. primigenius as “aurochs”, which is a fairly understandable and justified point and just be the continuation of the way the term was used for ages (leaving aside obvious confusions with the wisent).

The impression you give to non-experts without background knowledge is even more problematic. It might create a mentality like: “It’s not so bad when this or that species dies out, we can breed it back then anyway”. Why protecting wolves when you can “breed them back” from dogs anytime? Or, why protecting the last few Northern white rhinos or Java rhinos when you still have more or less close relatives to breed with (this is partly the same mentality the Quagga project is giving to people)?

You have to emphasize that the loss of each species, subspecies, wild-type, distinct population or whatever is an irreversible loss (at least when there is not enough preserved genetic material). Of course this message is more frustrating than enchanting. But something like “the original aurochs is irreversibly extinct – but we found something to fill its gap properly” might be teaching but encouraging at the same time. And even more: the plain truth.

Therefore I personally will not use the term “new aurochs” for the results of “breeding-back”, no matter how convincing they will be, and I also do not recommend it. It just creates a wrong impression in many respects.
The question is then how to call the desired results of “breeding-back” then, that will hopefully be as aurochs-like as possible and to some degree dedomesticated at some point. Well, the respective projects provide names to their respective cattle themselves: Taurus cattle, Tauros, Auerrind, Uruz cattle and not to forget advanced Heck cattle. But if you are looking for an umbrella term that can also be used for media purposes et cetera, I suggest simply using “aurochs-like cattle” and explaining what an aurochs was.


1 Pfeiffer, T.: Fossile Damhirsche in Neumark-Nord (Sachsen-Anhalt) – Dama dama geiselana n. ssp.. 1998.


  1. One difference between Przewalski's horse and a horse that feral for centuries, the Banker horse of North Carolina, is that you can not train Przewalski's horse for riding, but you can train a Banker horse for riding. I did see a video of a woman who was working on training a Przewalski for riding. She had already done it with a zebra, but it's a totally different process taking days for habituation with a young animal. Also in the book Beyond Words, the author states that no feral animal has ever regained the larger brain size of their wild ancestor. Just thought these two subject were germain to what you're talking about here.

    1. Yes, horses' behaviour towards remains domestic to some degree even living feral for some time. Cattle are known to develop shyness rather quickly while horses have remained quite tame or even obtrusive in grazing projects, what can cause problems.
      When I referred to behaviour in the article, I was mainly talking about social behaviour, natural instincts (f.e. herding, against predators etc.). Not only how they behave towards humans.

  2. With advances in genome editing technologies and the potential in the near future for an aurochs to be truly resurrected in a genetic sense, would it be fair to call cattle that are crossed with these 'de-extinct' aurochs, aurochs?
    As I believe you've mentioned before, it would be still necessary for genetic diversity to cross any such animals with 'advanced' cattle from backbreeding projects (or perhaps releasing a herd into the OVP would do the job).
    In your opinion, would the hypothetical offspring of these animals, dedomesticated aurochs like cattle with recent introgression from true aurochs, qualify as wild animals once again and earn the right to be called aurochs or aurochs 2.0?
    After all, don't most living Przewalskis have historic introgression from domestic and allegedly 'tarpan' mares?


    1. If one day aurochs would be truly recreated using cloning or CRISPR-Cas6, hybrids between aurochs and aurochs-like cattle should in my eyes be called exactly that: hybrids; of course it depends on the degree of hybridization. If you'd achieve a population of recreated aurochs that is 90-95% pure, I have no objections to calling them aurochs (with signs of cattle hybridizations). The majority of all extant American bison have cattle hybrids in their ancestry too.
      Yes, hybridization with domestic counterparts happened in a lot of species. Wolves, wild boar, horses... Basically all of them. But the difference is: the influence was always small enough not to greatly alter the integrity of the animals, their integrity as wild animals in particular. So it depends on the degree of hybridization. Maybe to some, 80% purity is acceptable already, but to me it is the genetic integrity of the important, defining traits that count.
      By the way, I preparing a blogpost on exactly that issue at the moment. There I will go into these aspects on a greater detail.