The elephant in the Pleistocene shop
How and why are people trying to bring back extinct animal species
On May 22, the world celebrates Biodiversity Day. American scientist, geneticist, molecular engineer and chemist George Church and an employee of the London Museum of Natural History, paleontologist Tori Herridge, having visited Yakutia and found perfectly preserved mammoth remains there, launched a broad public discussion about the possibility of "reviving" ancient animals and settling them in the Arctic. Konstantin Severinov, Doctor of Biological Sciences, professor at the Skolkovo Institute of Science and Technology and Rutgers University (USA), tells how and why scientists are trying to revive extinct species.
Late Pleistocene landscape in northern Spain with woolly mammoths (Mammuthus primigenius), horses, woolly rhinoceros (Coelodonta antiquitatis) and European cave lions (Panthera leo spelaea) with reindeer carcass. Photo: Mauricio Antón/Wikipedia.
Perhaps the most obvious ways to restore virtually extinct populations lie far away from cloning and other genetic experiments. A much more effective method is the conservation and restoration of habitats and the fight against poaching. However, these measures conflict with human economic activity and therefore can only slow down the extinction of species, but not prevent it in any way. It is also possible to support species on the verge of extinction in zoos – there, in principle, work can be carried out to preserve their genetic material and use it for artificial insemination and cloning. And such projects do exist.
Artificial insemination combines paternal and maternal genes in the same way as with normal conception, which allows you to get offspring with different sets of genes. Cloning gives copies of already existing animals. However, in both cases, if there are only a few founder individuals, the genetic diversity of the offspring will be very small, and maintaining the species will be difficult or even impossible due to the effects of negative mutations, which, for example, manifest in humans during closely related marriages.
If humanity for some reason decides to revive already extinct animals whose DNA turned out to be in relative safety - here, thanks to both popular culture and objective hopes for success, it is most often customary to recall mammoths extracted from permafrost – the task is further complicated. Consequently, various revival programs must have the genetic material of many individuals of the species being rescued from the very beginning. Any cloning during the transition from one species to another will require a significant amount of work and time to optimize the procedure. Because in this case, in addition to collecting a sufficient number of suitable samples of genetic material, females of a closely related modern animal species are also required, who could act as surrogate mothers.
For reproductive cloning, it is necessary to take an unfertilized egg of a female being (since it is unfertilized, it contains only one set of chromosomes/ genes; the second in a normal situation should be obtained during fertilization from a male). Then you need to remove the nucleus containing the chromosomes from this egg – this is called "enucleation". In the enucleated egg, it is necessary to introduce a nucleus taken from a cell of some tissue of the organism to be cloned. This nucleus will contain a double set of chromosomes, which means that fertilization is not necessary. For example, in the case of Dolly the sheep, the nucleus was taken from the udder cell. Then you need to stimulate the resulting egg to develop and plant it in the mother's uterus, usually not the one from which the egg was taken, so it will be a surrogate mother. If everything is fine, she will bear and give birth to a cub, which, from the point of view of a set of genes, will be identical to the organism whose nucleus was planted in the egg, will be its absolute copy. Using the example of Dolly, Jan Wilmot and his collaborators demonstrated for the first time the fundamental possibility of cloning. After that, of course, there were other successful experiments, however, as in sports, we remember only the champions. Moreover, sheep, unlike Ralph's rat cloned a little later, are cute and curly – it is obvious that they win from the point of view of PR.
This procedure works quite effectively: today cats, dogs and rats are cloned. It would seem that the same could be done with anyone, including the mammoth, whose revival has been talked about so much lately. To do this, you will need a surrogate elephant, a source of an enucleated egg (also an elephant) and a source of genetic information – fairly well-preserved genetic materials, of which there are many in Siberia and Canada, for example. According to George Church, a molecular engineer, chemist, professor of genetics at Harvard Medical School, who has gained worldwide fame in connection with his work in the field of genome sequencing and interpretation of the data obtained, an option is being considered with the use of an artificial uterus as a "surrogate mother" to avoid animal experiments. The only question is whether the genetic information obtained from the mammoth will be able to develop in the elephant's cage. These species are certainly very similar, but not at all identical: in fact, they are like humans and chimpanzees. The probability that the mammoth's genetic program will not work in someone else's cell and development will go wrong is quite high. Do not forget, of course, about such a fundamental problem as the state of the genetic material of ancient organisms, since DNA eventually breaks up into very short fragments under the influence of physico-chemical factors, and it is incredibly difficult to recreate a huge chain even with the use of advanced technologies.
However, this does not mean that the point in the question of the "revival" of mammoths has been set: the genomes of both mammoth and elephant are known, and it is known how they differ from each other. A more promising approach focuses not on cloning a mammoth, but on its gradual "creation" from an elephant. Technically, to do this, you need to gradually "redo", change certain DNA positions that distinguish an elephant from a mammoth and may be responsible for wooliness, tusks, ears, frost resistance, size, and so on. But even if we assume that scientists will be able to conduct a completely successful experiment, I think it will turn out to be rather a hairy elephant, especially if directed genetic editing of elephants is used as an approach. Then it will not be fundamentally different from breeding by breeding breeds of woolly cows grazing on the slopes of the mountains in northern Scotland.
In the north-east of Yakutia, the Pleistocene Park Reserve has been operating for several decades, where an experiment is being conducted to recreate the ecosystem of "mammoth tundras" from the last glaciation. Many rather ambitious projects are associated with this reserve, including the "resurrection" of the mammoth. In particular, George Church is also working in this area – he even came to Siberia with an expedition not so long ago. Church talks about creating frost-resistant elephants that could withstand low temperatures, coexist with other animals and make natural changes to the ecosystem. This is considered as one of the tools to counteract climate warming: mammoths tamp down snow, keeping the temperature low. In addition, they supposedly trampled bushes, uprooted trees, making room for grass. It absorbs less sunlight, which means the earth absorbs less heat, which also prevented the temperature from rising. I am not an expert in this field, but it seems to me that it is simply incorrect to predict the consequences of colonizing the current tundra spaces with mammoths or new "hairy elephants" for their transformation into a new mammoth steppe. We are talking about the introduction of hundreds of thousands of individuals in gigantic spaces. Obviously, if humanity really sets itself such a task (although its expediency is still not clear), then it is fundamentally possible to solve it, but the process will be gradual and will last for hundreds of years. There is a similar experience, however, without targeted genetic modification: for example, projects are underway to reintroduce musk oxen in various regions of the Arctic, including in Russia. These are one of the few representatives of the mammoth steppe fauna that survived the end of the ice Age, but by the middle of the XIX century their population was preserved only on the island of Greenland. On the territory of Russia, the experiment with the reintroduction of musk oxen began in the late 70s of the last century, when about 50 of these animals were imported to Taimyr and Wrangel Island. Today, their habitat has expanded significantly, and the population is 11-14 thousand heads on Taimyr and about 1.1 thousand heads on Wrangel Island. In addition, free-living populations have been created in the Polar Urals, Yamal, Yakutia, and the Magadan region. Similar projects have previously been implemented in other countries – for example, in Norway, the reintroduction of musk ox began back in 1924.
Will the attempt to revive the mammoth be just an attraction for the amusement of the venerable public? Hardly. The very formulation and attempt to implement such a task will require such scientific efforts and such progress in the field of genetics and genetic engineering, which will inevitably increase the ability of humanity to cope with the "human" problems facing it. For example, we will need these technologies to combat the ever-increasing number of mutations accumulating in our gene pool. And yet, while the prospect of the revival of long-extinct species is not directly on the agenda, it is worth thinking about all the ethical, moral and even philosophical issues related to this. After all, that's what makes us human.
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