Technologies for cloning, DNA sequencing and cell reprogramming make it possible to resurrect extinct animal species. RIA Novosti tells how far the technology has advanced, why the mammoth has not yet been cloned and whom scientists are going to revive in the future.
In March, when the last male of the northern white rhinoceros named Sudan died, experts said that in the near future these animals will disappear forever, since there are only two individuals left in the world - the females Najin and Fatu. However, the other day it was reported: the population can be restored. Using the latest reproductive technology, European biologists have created a "hybrid" embryo by combining sperm taken three years ago from Sudan with the eggs of its usual African relatives.
Now scientists are going to take eggs from the last two females and get already purebred embryos. Surrogate mothers from the South African population of white rhinos will most likely bear the cubs. Thus, the northern subspecies will recover, biologists are sure.
What is missing for successful cloning
Other extinct species cannot be resurrected so quickly. Cloning by classical technology, when the nucleus of a living cell is inserted into the egg, is impossible. In the soft tissues of mammoths, even very well preserved (found mainly in Yakutia), there are no such cells. Moreover, even in conditions of permafrost that are ideal for storage, cells, and hence DNA, are destroyed.
According to experts, within 158 thousand years after the death of the animal, half of the bonds between the nitrogenous bases of its DNA will be broken. That is why, for example, it is impossible to clone non-avian dinosaurs that became extinct at the end of the Cretaceous period (about 65 million years ago). Their DNA is destroyed, and proteins extracted from the bones of Tyrannosaurus and Brachilophosaurus and even partially decoded are not suitable for cloning these prehistoric giants.
Despite the good safety of the mammoth Yuki, scientists failed to extract DNA from its cells / RIA Novosti / Vitaly Ankov.
Promotional video:
However, sometimes it is possible to find separate whole cell nuclei in frozen tissue samples, but when the remains of ancient animals thaw, everything disappears. Scientists do not yet know how to preserve the structure of the cell during thawing.
New technologies and prehistoric giants
For at least two decades, there has been talk of the resurrection of the woolly mammoth (Mammuthus primigenius). Paleontologists have repeatedly found intact areas of the soft tissues of these animals. It was even reported that the blood of a mammoth was found, but, unfortunately, additional tests showed that it was just an interstitial fluid.
In 2011, researchers at the University of Pennsylvania reconstructed mammoth DNA by 70 percent, and in 2015, their colleagues at Harvard University transferred 14 genes of a prehistoric animal into a living cell of an Asian elephant. Using CRISPR / CAS technology, the scientists inserted genes into the elephant's skin cell genome for small ears, a thick layer of subcutaneous fat, and long hair.
However, many experts are skeptical. After all, it will not be a mammoth, but an intergeneric hybrid (modern elephants and ancient mammoths are distant relatives). Such hybrids are usually not viable. There is only one known precedent. The cub, born at the Chester Zoo in 1978 from an Asian elephant and an African elephant, lived for only 12 days.
Ancient cave lions
The cave lion (Panthera leo spelaea) has a better chance. If its nuclear DNA is reconstructed, they will try to insert it into the genome of the modern African lion. And they are rather close relatives with the prehistoric cave cat - much closer than mammoths and Asian elephants. According to the latest data, cave lions may be a subspecies of modern lions (Panthera leo).
There is more than enough biological material to reconstruct the DNA of a prehistoric cat. Three cave lion cubs were found in Yakutia in 2015 and 2017. Two bodies have survived completely, one without hind legs. While the efforts of scientists were not crowned with success, the safety of the remains was insufficient, and the researchers were able to isolate only individual fragments of DNA.
The carcass of a cave lion found during excavations in the Abyisky ulus in September 2017 / photo: Academy of Sciences of the Republic of Sakha (Yakutia)
Will the extinct birds fly
Evolutionary biologist and ecologist Ben Novak of the independent research organization Revive & Restore intends to give a second life to the wandering pigeon (Ectopistes migratorius) by 2025. The last representative of this species, which existed in the days of mammoths (the most ancient remains of these birds are hundreds of thousands of years old), died in 1914.
Biologists at the University of California Santa Cruz Paleogenomics Laboratory, with whom Revive & Restore works, have isolated and partially decoded nuclear DNA from four surviving pigeon carcasses and mitochondrial DNA from 41 samples. So Novak has something to work with.
The reconstruction and deciphering of the DNA of the Mauritian dodo, or dodo (Raphus cucullatus), which became extinct at the end of the 17th century, is being worked by an international team of scientists led by Beth Shapiro, professor of evolutionary biology at Oxford University. The DNA was partially recovered and compared with the DNA of living relatives - maned pigeons (Сaloenas nicobarica).
The Mauritian dodo, or dodo, died out at the end of the 17th century. Scientists hope to resurrect him in the future / CC BY 2.0 / Federico Moroni.
Yet deciphering the genome is one thing, but finding whole nuclei with unbroken chromosomes is another. Therefore, many do not share the enthusiasm of supporters of the idea of resurrecting extinct animals. Moreover, it is very expensive to recreate and maintain populations in the wild. Scientists from the University of Ontario point out that the choice in favor of the mammoth and other ancient animals will be fatal for many modern endangered species, since the resources for ecological conservation of both are not enough.
Alfiya Enikeeva