This post
plays with the possibility of a genetically resurrected, genuine aurochs. This
possibility emerged since a full genome has been resolved in 2015. This animal
would be a true aurochs in its original form, not domestic cattle with a number
of morphological/optic wildtype traits that might be considered dedomesticated
at some remote point of time of natural selection. What to do with such a
reconstructed aurochs, and would it make existing “breeding-back” projects
unnecessary?
Each time
it comes to genetically reconstructing an extinct animal, there are people
questioning the purpose of doing so. Well, reconstructing a genuine aurochs
would of course be for the same purpose of breeding aurochs-like cattle and
using it for nature restoration. It serves an ecologic good and is about
authenticity.
A number of
recent posts covered the probable genetic differences between aurochs and
domestic cattle, especially this one. I outlined why I believe that we
definitely need more than mere matches on SNPs and haplotypes as the genetic
differences between aurochs and cattle include a lot of aspects that have a
dramatic influence on the organism as a whole (neurology, endocrinology,
ontogeny, sexual dimorphism, immunology) and are responsible for the big
differences in morphology, development and behaviour that we see between the
wild animal called aurochs and its domestic counterparts. It is very likely
that these differences are caused by a high
number of loci whose individual role in the whole have not been resolved yet –
let alone the identification of wild vs. domestic alleles on these loci and
their distribution among domestic cattle today. This means that true
breeding-back of a genuine, pre-domestic aurochs is not possible by the current
state of knowledge and that it would take a very long time, dozens of decades,
because of the very high number of loci involved. Not to speak of the fact that
many of the original defining wildtype alleles probably have been lost in the
dramatic and intense process of domestication anyway.
Possibilities to genetically reconstruct an
aurochs
So that
true “breeding-back” is most likely not feasible as the necessary material is
a) not identified and traced down in modern cattle and b) very likely not fully
preserved anymore, how to get to a genuine, pre-domestic aurochs then? Luckily,
and finally, the full nuclear genome of a British aurochs bull from 8.000 years
ago was fully resolved in 2015 (see here), after the full mitochondrial genome
of the aurochs had already been known since 2011.
This makes
it feasible to truly revive a genuine, pre-domestic aurochs individual. The
fact that it is a male is especially advantageous, as male-specific aurochs
genes on the Y chromosome are known this way that otherwise would be unknown,
which would have an impact on sexual dimorphic traits. But how to get from the
genetic information to a life aurochs? Two methods are usually mentioned for
that are:
a) Cloning.
Both bantengs and gaurs have already been cloned successfully using a domestic
cow as a surrogate. For an aurochs, a domestic cow would be even more closely
related. For cloning, having the genetic information only is not enough. For
the process of somatic nucleus transfer, an actual aurochs tissue cell with an
intact nucleus that contains not only the DNA molecule but also the associated
proteins that are necessary for the regulation of the cellular processes are
needed in order to produce a viable embryo. As far as I know, what we have is
not enough to produce a clone, let alone the usual obstacles of cloning
(somatic nucleus transfer has a rather low success rate, and cloned individuals
often suffer from developmental problems).
b) Genome
editing with CRISPR-Cas9. This new method provides a lot of new possibilities regarding genetic
engineering and also the recreation of recently extinct species. It enables to
do very precise modifications of the DNA molecule and to change or exchange
genes point by point. By this technique it would be possible to take the DNA of
a surrogate cattle and exchange the domestic alleles with aurochs alleles,
producing a viable cell with aurochs DNA, and eventually leading to an aurochs
calf being born by a suitable surrogate mother. The mitochondria however will
still be of domestic origin, but they should have only a minor influence on the
phenotype of the organism. As for epigenetics, perhaps the difference would be
small as well as aurochs and domestic cattle are closely related, but we shall
see. However, as the DNA is from a somatic cell of a grown aurochs and not from
an embryo or calf, the individual might experience similar developmental issues
as clones do.
If a genuine aurochs was born
But when
finally a genuine aurochs individual is successfully recreated and born and
growing healthy, what do with it? It will be a male, and of course more than
just one individual with this genome can be created. At first, it will be most
interesting to see it growing and become a mature individual. Now that we have
something directly to compare with, we would see how far “breeding-back”
results or any primitive breed match the goal. Perhaps also some minor
surprises about its life appearance would revealed. Those reconstructed aurochs
bulls could go to zoos for display just like any wild animal. They could even
be used as new breeding bulls for any “breeding-back” herd, be it in grazing
projects, zoos or private farms in order to successively increase the
aurochs-likeness of those herds. One would have to be aware of the fact that it
is a wild animal though, with the behaviour and dangerousness of a wild bovine.
Building up a population
Theoretically,
even a female can be constructed by removing the Y chromosome and replacing it
with a duplication of the X chromosome of the aurochs bull. With that, you can
theoretically build up a herd, but the genetic diversity would of course be
extremely narrow. Probably a lot of the first-generation crosses if not all
would end up stillborn or as miscarriages because lethal alleles have a high
chance of homozygosity in the offspring. Furthermore, these aurochs, which are
basically from 8.000 years ago, might also be vulnerable to many modern cattle diseases.
The only way to create a viable population of aurochs would be to acquire more
genetic diversity. If one is optimistic, perhaps the full nuclear genome one or
even more further aurochs individuals, in the ideal case one of another time
and region, can be resolved. In this case it might be enough – if we get, say,
the full genome of five individuals from different regions of Europe and
different geological times, we would probably have a way higher genetic
diversity than in the Wisent already. But if one is pessimistic, that one
British aurochs bull might remain the only individual for which the full genome
can be resolved. In this case, there would be only one way to achieve more
genetic diversity in order to create a viable aurochs population: controlled,
systematic hybridization with domestic cattle.
I would use
a technique called absorptive breeding, where the hybrid offspring is
constantly back-crossed with pure individuals of the parental generation until
the level of “purity” desired is achieved. This way, a fifth-generation hybrid
would be genealogically almost 97% pure. Most alleles would be aurochs alleles,
but it would also include domestic cattle alleles (however, genealogy is not
everything – theoretically it is also possible that such an animal still has
50% domestic alleles, although statistically unlikely). It would be best to not
to use just any domestic cattle, but to use robust and healthy breeds to
introduce necessary immunological alleles for the resistance against modern
cattle diseases, f.e. Chillingham cattle and other robust northern breeds, and
primitive landraces.
I would
build up a herd composed of third, fourth and fifth generation hybrids created
by absorptive breeding, keep them under semi-feral conditions (therefore, using
them under the frame of a grazing project in a natural area would be the best
option, although their behaviour would be challenge to conventional grazing
projects) and then let them breed for themselves but would still select the
offspring. This is necessary in order to achieve the goal: the goal is to add
genetic diversity for resistance against diseases and overcome developmental
problems, but at the same time not altering the biologic integrity of these
wild cattle. That means artificial selection should focus on breeding out
individuals with obvious signs of hybridization that would show in the
phenotype (remember: phenotype not only refers to morphological/optical
aspects, but also such as behaviour). The genuine, unhybridized aurochs
individuals should always be the template for that. At the same time,
individuals that cope well with the natural circumstances, are fully fertile,
give birth to healthy offspring and apparently are resistant to diseases should
remain in the population. Since people have to work with those cattle, tame,
relaxed, less aggressive and less nervous individuals will of course be easiest
to handle. However, one has to pay attention not to favour these individuals
and therefore domesticate those aurochs hybrids once again (which would be
rather ironic). One would have to regard them as wild bovines, keep and handle
them like wild bovines. It works with wisents, bison and buffaloes, so it
should work with aurochs as well.
After some
generations, a viable population of aurochs would have been created. The
likelihood of deleterious alleles becoming fixed homozygously has been drastically
reduced by hybridization, and hybridization introduced a lot of new alleles for
the resistance against diseases and cope with other obstacles, while artificial
selection preserved the biological integrity of the wildtype. Furthermore,
there would still be pure individuals to backcross with, even if you have to
genetically produce them again. However, alleles for domestic mutations that
would show in the morphology of the animals would remain in the population for
some time unless they are effectively selected against. It would be comparable
to the situation of many American bison, where you still occasionally see
individuals with vestiges of hybridization with domestic cattle around 1900
(for example here), but invisible in the majority. This could include divergent
horn shapes or colour variants, especially when the alleles are recessive.
The perception of resurrected aurochs
A lot of
people, especially conservationists, will complain about those aurochs having
domestic cattle introgression. They will argue that these aurochs are not
“pure” and therefore not genuine. This exhausting mindset is the result of
underestimating the role of hybridization in evolution and the importance of
genetic diversity and might one day cost the wisent’s life as a species, a mindset that is
part of the 19th and 20th century conception of nature as
a static and “highly balanced” system to which we humans are the “destabilizing
factor”, a conception that is not tenable for obvious reasons. Not only is
hybridization a not as rare aspect of speciation as once thought (I plan to do
a post on that), in this case we would have introgression into a wildtype from
its domestic descendants. Hybridization between wild and domestic forms takes
place everywhere they share the habitat, and is also evident for wolves, wild
boars and also been proven for Holocene wild horses. Nobody would consider
timber wolves or McKanzie wolves less “genuine” because their coat colour
diversity is suggested to be influenced by ancient domestic dogs, or condemn
wild boar populations because they share some domestic haplotypes – so why not
accepting a population of genetically resurrected aurochs whose genetic
diversity has been increased by controlled, systematic introgression of some of
its domestic descendants?
The idea of
hybridizing those aurochs with domestic cattle in order to increase genetic
diversity of course evokes the question which cattle would be best-suited to do
this. As mentioned above, these cattle should a) be as healthy and genetically
diverse as possible, b) as less-derived as possible in order to introduce as
few derived or deleterious alleles as possible – two points that often go hand
in hand. Probably it would be best to choose a handful of less-derived, robust
and healthy landraces to hybridize with. Once again a balancing act has to be
done. If one would hybridize only with a herd of a breed like Maronesa, the
impact on the visible traits would be very low in the outcome, but the gain of
genetic diversity would be narrow. So more than one breed has to be chosen, and
from more than just one region. You can find suited cattle even in Asia in the
form of the turano-mongolian breeds (see here). But importing sufficient
numbers of cattle is very costly and effortful, which is also one of the
reasons why many grazing projects and “breeding-back” projects use breeds that
are already local.
And here is
where already existing “breeding-back” cattle are important and which is why I
think they would not at all become meaningless if genuine aurochs would one day
be reconstructed. If such an aurochs project is to be set up on a large,
semi-natural area somewhere in Europe outside the Mediterranean range, “breeding-back”
cattle would be the most aurochs-like cattle available and since they are
composed of a number of landraces, would introduce genetic material of a number
of breeds. If such a project came about in Germany or the Netherlands, and one
choose to use Taurus and Tauros individuals as a base, you would have the
genetic material of at least eight breeds already (Heck cattle, Sayaguesa,
Chianina, Maremmana, Limia, Maronesa, Pajuna, Highland). This also means that
the range of undesired domestic traits is large, though, but it will be
minimized by absorptive breeding and selection, just like in the case of bison
with domestic cattle introgression.
What to do with resurrected aurochs?
So if one
finally has the desired viable population of genuine aurochs, what to do with
them? At first, it might be wise to create a herd book for them, perhaps right
from the beginning, like it has been done for a number of endangered species.
This can be advantageous to maintain an overview over the genetic composition
of the animals after they are spread to other breeding sites. Surely some of
them can be sold to zoos for preservation and education. They can also be used
for grazing projects and private breeding by aurochs fanciers, but I doubt that
this will be a common use for genuine aurochs, especially the latter one. These
animals would display wild behaviour and would be difficult and dangerous to
handle just like wisents, bison and wild buffaloes. There is a reason why
domestic cattle are used that commonly in grazing projects, but there are only
a handful that work with wisents, although the wisent is a native wild animal
here whose reintroduction should be preferred over that of a domestic proxy.
The
ultimate goal would be to not only create a population that can be considered
“pure” or more or less pure in the eye of enthusiasts but also in those of the
IUCN. A recognition of those reconstructed aurochs as aurochs and wild animals
from an “official” organization would be a great help for the acceptance of
these cattle as wild animals and legitimate their reintroduction into nature
areas. Zoos would also help to spread and increase the population number, where
they could also be used for education.
Very good article, congratulations! And by the way Merry christmas and happy new year!
ReplyDeleteVery good post congratulations and thank you. One question do you know if someone is working on it? I know that a few years ago the University of Krakow was working on the reconstruction of the Auroch genome.
ReplyDeleteDaniel could you please email me at primoculturefarms@gmail.com I thought I had your contact info but I seem to have misplaced it.
ReplyDeleteAre you from Carnivora?
ReplyDeleteThere must be a huge amount of aurochs bones available in institutions all over Europe. Most probably have little detectable intact dna in them but a certain amount from Northern Europe should come from cold conditions that their genomes could be available for sequencing. I believe the cost of sequencing has hugely reduced since the human genome project. So if gene editing is to proceed, it shouldn't be too hard to create additional aurochs copies; the reborn aurochs could have a lot of diversity and very soon there would not be a need to cross with domestic cattle but with existing recreated aurochs. This could and should be done with the Wisent too; sequencing of remains from the last few hundred or thousand years so that diversity could return without having to crossbreed with American bison. Sounds easy but probably extremely expensive to bring to fruition.
ReplyDeleteFor the first part above I am saying as many aurochs should created as possible from genomes derived from bones all over Europe to give good diversity.
ReplyDeleteMaybe a cloned Auroch would just get crossed with its closest domestic relatives. So if the Auroch is from the strain that spread to northern europe at the end of the ice-age, this would be mostly Pajuna.
ReplyDeleteI m spaniard and my English is bad. I love the auroch (uro in Spain) and I read this blog since a lot of time with the traslator but never I write because my languaje is bad. I want to show yo this:
ReplyDeletehttp://www.bizkaia.eus/home2/Temas/DetalleTema.asp?Tem_Codigo=4414&Idioma=CA
I guess those are Terreno?
DeleteYes, they are relatives of the alistano-sanabresa and the sayaguesa.
DeleteYou know about our primitives horses? they are very similar to the konik. the exmoor and the hucul, we have a lot, garrano, losino, asturcon, monchino, pottoka... They look as tarpan a bit.
DeleteSorry for my bad english.
DeleteI love this article, it pretty much answers and confirm some of my suspicions. But I do have a couple questions: What specific breeds would you use to breed with the resurrected Aurochs? I know that you have mentioned some, but if you were make a specific list, what would they be? In that case, could the Heck and Taurus (Tauros?) cows be used to breed with the Aurochs?
ReplyDelete