By scientific standards, the relatively recent extinction period of mammoths and its cause - a glacier moving south - allow scientists to still hope that sooner or later a frozen animal corpse will be found, which may be used for its revitalization. Cloning, DNA sequencing and cell reprogramming technologies make it possible to resurrect extinct animal species. And after the successful cloning of Dolly the Sheep, these hopes turned into almost certainty. How far have the technologies advanced, why haven’t the mammoth been cloned so far, and which countries are confident that they can bring the ancient animal back to life?
Cloning a mammoth requires a living cell. And if there is at least some glimmer of hope with the mammoth, then it will not work so quickly to resurrect other extinct species. Cloning by classical technology, when a living cell nucleus is inserted into an egg, is impossible. In the soft tissues of mammoths, even very well preserved (found mainly in Yakutia), such cells are still not found. But, nevertheless, for two decades there has been talk of the resurrection of the woolly mammoth. Paleontologists have repeatedly found intact pieces of the soft tissues of these animals. Even the blood of an ancient animal was discovered, but, unfortunately, additional tests showed that it was just interstitial fluid.
What countries besides Russia are interested in cloning a mammoth and how close are they to the revival of an ancient animal?
The leader in the fulfillment of such an ambitious goal is South Korea. The geneticists of Sooam Biotech Research Foundation are engaged in the search for living cells in permafrost and the revival of an ancient animal with the direct participation of scientists from the Northeast Federal University. The personality of the director of the Research Foundation, Hwang Woo-suk, is quite famous in the scientific community. Despite the violation of bioethics, seedy deeds against scientific and human morality, results falsification, the authority of the scientist is not in doubt. Today he is a recognized expert in the world animal cloning science. Today, his foundation successfully clones pets for practical purposes.
Japan is the first foreign country, scientists of which in the late 90s came to look for living mammoth cells in the Russian Far North. They were headed by Professor Akira Iritani, who at that time was the director of the Institute of Advanced Technologies at Kinki Private University in the Japanese Nara Prefecture. In 1997 and 1999, Yakut and Japanese scientists searched for "fresh" corpses of mammoths in Kolyma. Living cells were not found then, there was only a piece of skin that scientists took to Japan. There were difficulties with permission to export. They waited especially long for the permission of the Ministry of Culture. As a result of the study, it turned out that the found fragment belonged to the woolly mammoth. According to Semyon Grigoriev, today Japan is collaborating with the Academy of Sciences of Yakutia on cloning a mammoth.
The Japanese managed to achieve real results only this year. Scientists took 88 nuclei of mammoth cells containing DNA, and placed them in the eggs of the mouse, which were released from their own DNA. As a result of the experiment, five samples demonstrated biological reactions that occurred immediately before cells began to divide. They “came to life” - they were able to eat and even could correctly build chromosomes. However, the success of the experiment is only partial. After all, the most important thing - cell separation - did not happen. This process is the biological basis of life. Without this, it is impossible to truly revive a mammoth.
“This indicates that, despite the past years and deep damage to the cells, the activity of the latter can occur and they can partially be recreated. So far, most studies have focused on the analysis of fossil DNA, and not on whether these cells function or not," noted one of the authors of the study, Kei Miyamoto.
Recently, biologists from China and Russia also tried to find out the safety of mammoth DNA. The nuclei were extracted from the muscle cells of the baby mammoth Yuka, the least damaged ones were taken and transplanted into the eggs of mice. For comparison, a similar experiment was conducted with the nuclei of African elephant cells.
In some cells, processes started that usually occur before division, however, neither the appearance of chromosomes, nor the division did. DNA was damaged more than they hoped, scientists admitted. But even such a result shows that after millennia, active protein components remain in the tissues of prehistoric animals.
"De facto, cloning a mammoth by conventional nuclear transfer technology is impossible, but our method allows us to evaluate the biological activity in the cells of extinct animals," summed up the Chinese scientists in their scientific work. That is what leaves hope for the possibility of a revival of the main representative of the mammoth fauna.
One of the common myths about cloning is as follows: the presence of DNA and the scrutiny of genome are not identical with the concept of cloning. The animal’s DNA can be in any state, and cloning requires a so-called living cell with a whole nucleus and intact DNA. Therefore, European scientists are actively engaged in the study of the mammoth genome, and not its cloning. This will help recreate the correct genetic sequence of mammoth DNA.
According to Albert Protopopov, Doctor of Biological Sciences and the head of the Department for the Study of Mammoth Fauna of the Academy of Sciences of the Sakha (Yakutia) Republic, the Harvard University project is more realistic and more likely to succeed. Molecular engineer guru George Church and his team plan to use one of the genetic engineering techniques that can be used to “cut” sections of mammoth DNA with high precision and “paste” them into elephant stem cells. In 2015, scientists managed to transfer 14 genes of a prehistoric animal to the living cell of an Asian elephant. The scientists inserted genes responsible for small ears, a thick layer of subcutaneous fat and long hair into the genome of skin cells of an elephant. According to the authors of the experiment, today they have already revived dozens of mammoth genes and are actively testing them on elephant cells. Thus, in the future, scientists will merge the genes of the two species of mammals to create their hybrid. They plan to grow a mammoth in an artificial uterus, without using a female elephant as a surrogate mother. According to scientists, this process will take at least 22 months. Who knows, maybe scientists from America will present a great gift for the 100th anniversary of the Yakut Autonomous Soviet Socialist Republic.
For this, an agreement was signed for the supply of biomaterials, similar to that which was signed with Japanese colleagues. In general, Yakut scientists are moving towards achieving an ambitious goal in different ways, collaborating with a number of countries. According to Semyon Grigoryev, today the genome of an ancient animal has already been deciphered, then everything depends on technology.
The mammoth genome is deciphered. What's next?
Yet deciphering the genome is one thing, and finding whole nuclei with unbroken chromosomes is another. Therefore, many do not share the enthusiasm of the supporters of the idea of the resurrection of extinct animals. In addition, quite practical issues get involved in scientific ones: recreating and maintaining populations in the wild will be very expensive. Scientists from the University of Ontario indicate that the choice in favor of mammoth and other ancient animals will be fatal for many modern endangered species, since there are not enough resources for environmental conservation. Today no one doubts that if the results of the experiments are successful, it will not be a mammoth, but an intergeneric hybrid, because modern elephants and ancient mammoths are very distant relatives.
“The maximum that can be done even if the mammoth DNA is perfectly preserved is to create a transgenic elephant. That is, an elephant with mammoth genes included in its DNA. There will come out not a mammoth or an elephant, but as they sometimes write in the media - an elephant mammoth or a mammoth elephant,” said in an interview one of the most respected mammoth experts in the world, Scientific Secretary of the International Mammoth Committee, Alexei Tikhonov.
This is a major insurmountable obstacle to mammoth cloning. Even if it was possible to revive the mammoth cell and successfully transplant its nucleus into the elephant's egg, the embryo would not form. This was already convinced by Korean scientists who were trying to clone a fox using wolf eggs. This experience showed that even within the canine family such an experiment would not succeed. Today, only one precedent is known for the birth of an intergeneric hybrid. The cub, born in Chester Zoo in 1978 from the Asian elephant and the African elephant, lived only 12 days.
However, science does not stand still. Several years ago, scientists unequivocally talked about the fact that it is impossible to clone a mammoth. But over two decades, scientists have achieved tremendous and incredible results, making a confident step in deciphering the genome of ancient animals. On the one hand, there has been a scientific revolution in animal cloning, and on the other, an evolution of the thoughts of scientists in this field. After all, who knows, having “revived” one extinct representative of the fauna, someday it will nevertheless be possible, if not in the near future and certainly not by cloning, to bring the ancient giant back to life.
Prepared by Andrey SHILOV