By restoring the genome of extinct animals, it will one day be possible to bring saber-toothed tigers, woolly rhinos and even Neanderthals back to life, scientists believe. And although technology does not yet allow the revival of those creatures whose DNA has been restored only in a computer form, specialists already have the genomes of several extinct species at their disposal
The mechanism of creation of any living creature is recorded in its DNA, and therefore in November last year, when experts published an almost complete sequence of mammoths' DNA, heated debates began about whether it is possible to bring this animal back to life, reminds the Vremya Novostey newspaper.
It is not yet possible to create a living being from a genome that exists only in computer memory. But the day will come when scientists will definitely try to do it, says Stephen Schuster, a molecular biologist at the University of Pennsylvania who led the reconstruction of the mammoth genome.
In any case, only those living beings whose complete genome is known to scientists can be resurrected. It is difficult to obtain a genome, because after death, DNA is rapidly destroyed by sunlight and bacteria. However, under certain conditions, DNA can be preserved: for example, in permafrost or in a dry climate, without access to sunlight.
Nevertheless, even under ideal conditions, the lifespan of any genetic information does not exceed a million years. That is, it will be impossible to resurrect dinosaurs. “It is worth trying to extract DNA only from those animals that are no more than 100 thousand years old,” explains Schuster.
“It's hard to talk about the absolute impossibility of anything,” says Svante Paabo, an employee of the Max Planck Institute for Evolutionary Anthropology, “but the resurrection of extinct animals requires technologies that are so superior to what we have now that I cannot imagine how it can be do.
Recipe for resurrection
Resurrection of an extinct animal requires well-preserved DNA, several billion building blocks of DNA, a suitable surrogate mother, and highly advanced technology.
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The first step is to extract DNA from an extinct animal and obtain a complete genome. At this stage, serious difficulties await geneticists, since the genomes of extinct animals will most likely contain many serious errors. Then it is necessary to create the DNA of an extinct animal in the required amount, inaccessible to modern science.
After that, the chromosomes will have to be inserted into an artificial nucleus, and the nucleus - into the surrogate mother's egg. Here, the search for a surrogate mother and obtaining her eggs can be a big problem. It should not be forgotten that no one has yet managed to clone birds and reptiles.
Finally, you will have to raise a baby from the embryo, which also requires a surrogate mother. Finding surrogate mothers for many extinct animals is a daunting task.
List of species claiming resurrection
Despite all the existing problems, the staff of the authoritative popular science magazine New Scientist suggested that sooner or later scientists will be able to create the technologies necessary for resurrection, and made up a dozen of disappeared living things that may one day return to Earth. When compiling the list, the authors took into account not only the possibilities of the resurrection itself, but also how interesting the prospect of recreating these animals is for people.
1. Saber-toothed tiger (Smilodon fatalis)
Extinct about 10 thousand years ago.
DNA safety - 3 (five-point system).
Suitable surrogate mother - 3 (on a five-point scale).
This predator with long canines, which could reach 20 cm, lived in North and South America. The remains of saber-toothed tigers are well preserved in the resin mines in La Brea (Los Angeles), but the resin makes it difficult to extract DNA, so scientists still do not have DNA suitable for resurrecting smilodons.
The remains of saber-toothed tigers preserved in permafrost may be the best sources of DNA. If the genome of the saber-toothed tiger can be obtained, then the most optimal egg donor and surrogate mother could be an African lioness.
2. Neanderthal (Homo neanderthalensis)
Extinct about 25 thousand years ago.
DNA safety - 1/5.
Surrogate mother - 5/5.
Experts hope to get a sketch of the genome of the Neanderthal this year, and “it will take another couple of years to obtain a genome suitable for work, comparable to, say, chimpanzees,” says Svante Paabo.
Paabo and his colleagues hope to find out with the help of the genome how we differ from the Neandenthals, but the genome can be used to resurrect them. Due to the very close relationship, the ideal surrogate mothers and egg donors are certainly people. However, now it is difficult to imagine that someone would dare to experiment so dubious from an ethical point of view.
3. Short-faced bear (Arctodus simus)
It died out about 11 thousand years ago.
DNA preservation - 3/5.
Surrogate mother - 2/5.
Along with this huge beast, even a polar bear, the largest land predator on the planet today, would look like a dwarf. Straightening to full growth, the short-faced bear reached almost 3.5 m. As for the weight, in the largest individuals it reached 1 ton. There should be no problems with obtaining DNA, because many remains of these animals have been preserved in the permafrost.
The closest relative of the short-faced bear is the spectacled bear that lives in South America. Unfortunately, a spectacled bear weighs almost ten times less than a short-faced bear, and a female of this species will be difficult to use as a surrogate mother.
4. Tasmanian tiger (Thylacinus cynocephalus)
It died out in 1936.
DNA preservation - 4/5.
Surrogate mother - 1/5.
The last Tasmanian tiger, or thylacin, named Benjamin, died at the Hobart Zoo in 1936. The preservation of various tissues less than a century ago suggests that geneticists will be able to easily obtain good quality DNA and a complete thylacin genome.
Thylacin-type marsupials are easier to resurrect than most other mammals. Their pregnancy lasts an average of three weeks, and a simple placenta is formed only for a short period. This means that the risk of rejection by a surrogate mother of another species of marsupial animals of the embryo is minimal. For thylacine, the Tasmanian devil is perhaps the most appropriate donor and substitute. After birth, the cub can be fed with milk in an artificial bag.
5. Glyptodon (Doedicurus clavicaudatus)
It died out about 11 thousand years ago.
DNA preservation - 2/5.
Surrogate mother - 1/5.
The Glyptodon, a battleship the size of a Volkswagen Beetle, once roamed the vastness of South America. Since no frozen glyptodon corpses have survived, obtaining DNA will depend on whether more or less preserved remains can be found in some cool, dry cave.
There is a more serious problem - the closest relative that could serve as a surrogate mother is a giant battleship weighing only 30 kg. The huge difference in size will undoubtedly prevent the female from bearing the fetus of an extinct relative before the required date.
6. Woolly rhinoceros (Coelodonta antiquitatis)
Extinct about 10 thousand years ago.
DNA preservation - 4/5.
Surrogate mother - 5/5.
Resurrection of the woolly rhinoceros is a very real challenge. As in the case of the mammoth, many remains of these animals have been preserved in the permafrost. A big plus for obtaining well-preserved DNA is the presence of hair, horns and hooves.
The woolly rhinoceros has a very close relative - modern rhinos, whose females could well be surrogate mothers. Unfortunately, today's rhinos are on the brink of extinction themselves.
7. Dodo (Raphus cucullatus)
Extinct around 1690.
DNA safety - 1/5.
Surrogate mother - 3/5.
In 2002, geneticists from the University of Oxford received permission to extract a piece of the thigh bone of the best-preserved specimen of the dodo with feathers and skin, which is kept in the Natural History Museum in London. Alas, scientists were able to obtain only tiny fragments of mitochondrial DNA. It was not possible to obtain this from other dodo remains, although there is still hope that someday it will be possible to find an even more preserved specimen. If it is possible to obtain DNA and a genome, then the pigeons will most likely have to bring their famous relatives back to life.
8. Giant ground sloth (Megatherium americanum)
Extinct about 8 thousand years ago.
DNA preservation - 3/5.
Surrogate mother - 1/5.
The growth of this giant reached 6 meters, and it weighed 4 tons. Its relatively recent disappearance means that some of the remains still have hair and represent an excellent source of DNA.
The whole difficulty for resurrection will be in finding a suitable surrogate mother. The closest living relative of this beast is a three-toed tree sloth, but it is much smaller than its huge ancestor. From a tree sloth it will be possible to obtain eggs, and from them an embryo, but the embryo will quickly outgrow its surrogate mother.
9. Moa (Dinornis robustus)
It died out at the beginning of the 19th century.
DNA preservation - 3/5.
Surrogate mother - 2/5.
Extracting moa DNA from the well-preserved bones of these giant birds and even eggs preserved in the caves of New Zealand, as well as obtaining the genome, is not difficult. As for the surrogate mother, it can be a female ostrich, although ostriches are only distant relatives of moa.
10. Irish Elk (Megaloceros giganteus)
Extinct about 7.7 thousand years ago.
DNA preservation - 3/5.
Surrogate mother - 2/5.
The growth of this elk, which lived in the Pleistocene and lived throughout Europe, at the withers exceeded 2 meters, and the distance between the tips of the antlers reached 4 meters. He was more a deer than a moose. The closest relative of the Irish elk is the fallow deer. These two species split about 10 million years ago. The large gap between them will make resurrection very difficult.