On January 6, 2000, a wild mountain goat named Celia was crushed by a falling tree on the cliffs of the Spanish Pyrenees - this is how her entry into history began, writes the New York Post.
Celia was a bucardo - a rare species of wild goat - and, as it happens, the last of her kind.
But a group of Spanish scientists had other ideas about this. Ten months earlier, they had taken a sample of Celia's tissue in hopes of saving her species from extinction.
If it worked, suggests science journalist Helen Pilcher in her new book The Return of the King: The New Science of Rebirth, it "would be a defining moment in Earth's history - the end of an irreversible extinction."
Two years later, "cells with Celia's DNA were injected into goat eggs, stripped of their own genetic material. After a brief electric shock, the eggs began to divide."
Embryos were implanted in the wombs of goat surrogate mothers, and although most pregnancies aborted, one was successful.
History came to a close on July 30, 2003, when one of Celia's clones was born, marking the first time an extinct species has returned from oblivion. Unfortunately, her health failed. Her lungs were "deeply deformed" and she died seven minutes later - the first time in history that the species had disappeared twice.
Many of us learned the concept of "rebirth" from the movie "Jurassic Park", which marked the rise in popularity of dinosaurs.
But this idea was not a wild invention of a Hollywood screenwriter.
Pilcher writes that in the 1980s, John Tkach, founder of an "underground group of scientists and clinicians in Bozeman, Montana" who called themselves the Extinct DNA Research Group, performed an intriguing thought experiment.
“What if, many millions of years ago, a hungry mosquito that dined on a dinosaur ended up in amber right along with its last supper in the stomach? If you could get a dinosaur blood cell from this mosquito and plant it in an egg from which their own DNA has been removed "maybe it would be possible to" grow a dinosaur ".
This theory was implausible, but not completely crazy. Entomologist George Poinar of the University of California at Berkeley has dedicated his career to studying insects that were trapped millions of years ago in the resin of trees that turned into amber. Outwardly, they were usually intact, but their insides were in "depressing chaos", but in 1980 he found a fly that "defied expectation" - its cells remained intact for 40 million years. This was exactly what Tkach theorized about.
The publication of Poinar's findings excited the scientific community, including a "tall, awkward man" who visited his lab to ask questions about "resurrecting life forms from amber." Poinar didn't think about it until years later when he was informed that a new book, soon to be made into a movie called Jurassic Park, was thanking him. The book's author, Michael Crichton, who was the tall, awkward visitor, "used (this visit) as a scientific basis for his novel."
So what's going on with attempts to revive dinosaurs now, decades later? "A dinosaur living in our world is not a fantasy," Pilcher writes in his book. But while there are respected scientists who believe it's possible, she also explains that we shouldn't roll the lip. After all, finding material to create a dinosaur is not an easy task, to put it mildly.
"To revive an animal, you need a source of its DNA," Pilcher writes. "But all we have for dinosaurs is their fossilized remains."
Most of our information about dinosaurs comes from fossils, and "one of the tenets of paleontology is that once fossilization is complete, any organic trace of the animal is gone," Pilcher writes.
Despite this, beginning in 1992, paleontologist Mary Schweitzer made a series of discoveries, including determining that dinosaur fossils "contain molecules found in red blood cells" and that certain types of dinosaur tissue could "survive fossilization."
As she continued her work, she found that the protein molecules also survived, prompting The Guardian to write that her findings "teased the possibility that scientists might one day rival Jurassic Park by successfully cloning a dinosaur."
However, this is only the first step in finding enough dinosaur genetic material to recreate them.
"Even though dinosaurs were made of protein (and many other molecules), we can't somehow reconstruct one of the few disparate collagen particles. It's like trying to build the Lego Star Wars Millennium Falcon from 5,195 pieces with just a few bricks." and pictures on the box," Pilcher writes. "Without instructions, it's impossible to know what other bricks should be or how to put them together."
These "instructions" are also known as DNA, and it is still unclear how long such a "hopelessly fragile molecule" can survive. In the 1990s, a series of finds were claimed to have recovered DNA dating back to 120 million years ago, including DNA from an 80-million-year-old dinosaur bone. These claims were debunked by Nobel Prize-winning biochemist Thomas Lindahl, who showed that "because of the way DNA is broken down, it simply cannot last all that time."
He was proven right in 2012 by a study "which found that DNA has a half-life of just 521 years." This means that "after 6.8 million years, every link would have been broken, making DNA recovery from even older fossils absolutely impossible."
It turns out that there was no DNA in the fossils found in the 1990s and that the experiments accidentally "evolved bits of modern DNA from the environment." Recently, using more advanced equipment, scientists were able to confirm that the oldest DNA found to date came from "a 700,000-year-old horse found frozen in Canadian permafrost" and that the oldest human DNA comes from "hominini ( one of the types of ancient people) 400 thousand years old, found in an underground cave in the Atapuerca mountains in Spain".
Dinosaurs became extinct about 65 million years ago. So while a 99-million-year-old dinosaur tail found in amber, containing bones, soft tissue and feathers, has stirred up scientists studying ancient animals, the decay of DNA means it won't help resurrect them.
Nevertheless, Schweitzer believes that finding dinosaur DNA could one day be possible. “If there is a way to get DNA from a fossil that is 700,000 years old, then why not a million?” she said to Pilcher. “And if you can get DNA from a million-year-old fossil, then you can also succeed from one whose age is 7 or even 70 million years.” ?"
This quest was Schweitzer's life's work, and she continues it to this day. There are some scientists, including Schweitzer's boss, Jack Horner, Jurassic Park's science consultant and the inspiration for the character Sam Neill in the film, who are wondering if dinosaurs could be resurrected in a different way.
"Horner believes he could create a dinosaur in as little as 10 years, and without having to resort to ancient DNA," Pilcher writes. "All he has to do is reverse evolution." The first step in this business is to start with a modern descendant of the dinosaur. This is the easy part, since birds and alligators are the evolutionary descendants of theropods, a species of bipedal dinosaur that includes the T-Rex.
Horner's idea is to take an embryo of a modern bird and somehow select its ancient evolutionary characteristics, given that "sometimes in modern living creatures ancient features are prominently manifested." Horner has to figure out what the instructions are and then find a way to reactivate them, Pilcher writes.
"By experimenting with chick embryo development programs, he hopes to convince them to release their inner dinosaur; develop dinosaur-like characteristics like teeth and tails." In short, Horner is trying to breed chickens that will be more like dinosaurs. Despite this, the chances of a dinosaur resurrection are about the same as seeing one driving an Uber.
Scientists are currently trying to revive species as genetically diverse as the dodo, passenger pigeon and woolly mammoth, but have run into obstacles including lack of DNA, lack of proper incubation environment and the risk of cruelty to would-be surrogates.
On a more positive note, Pilcher writes that the science of rebirth can help prevent species extinction. "There are a lot of projects where people deliberately take cages from endangered animals, [including] picking up animals that have been hit on the road and taking cages from them," says Pilcher. "Entire museums are full of all these stuffed animals, and while they don't have living cells, they often have dead cells that contain DNA."
She notes, for example, that there are only three northern white rhinos left in the world that are unable to reproduce due to age and other factors. Scientists have already taken skin cells from rhinos in the hopes of one day converting the material first into stem cells and then into eggs that can be fertilized with sperm samples they also obtained. It is highly possible that scientists will be able to breed the northern white rhino in vitro within the next three to 10 years, Pilcher said.
However, if you really want to see dinosaurs come to life, better mark 2018 on your calendars when the next Jurassic Park sequel is released.
The dream of resurrecting dinosaurs, mammoths and other extinct animals constantly pops up in the press, although the vast majority of scientists are very skeptical about this idea. Will people ever be able to walk in the park of any period?
Alexander Chubenko
Let's start with the worst news: Jurassic Park is pure fantasy. Neither in the mosquitoes immured in amber, nor even in the petrified remains of dinosaurs, even traces of DNA remained. Most likely, even before the start of filming the first film of the epic, her scientific consultant, paleontologist Jack Horner, had no doubts about this either. Although (certainly not without the influence of working with Spielberg) he developed a project to create a dinosaur-like creature, but more on that later.
And recently, the dream of dinosaurs was finally put an end to. Danish and Australian paleogeneticists have analyzed DNA from the bones of more than 150 extinct New Zealand giant birds between 600 and 8000 years old and calculated that (in any case, under conditions of storage of bones in the ground, and after - in museums) the half-life of DNA is 521 years . The conclusion is unequivocal: even in permafrost, after a million and a half years, the strands of fossil DNA will become too short to obtain information about the sequences of its nucleotides. The remains of the last dinosaur are 40 times older - dreamers can relax and dream about something more mundane. For example, about mammoths.
Mammoths: two approaches to the dream
Japanese geneticist Akira Iritani, one of the leaders of the Mammoth Creation Society, in the mid-1990s still hoped to find a viable egg and sperm in the carcasses of Siberian mammoths, and implant the result of their fusion into the uterus of an elephant. Realizing the unreality of such a hope, this strong old man (he is now a little over 80) did not stop trying to get at least the nucleus of a somatic (preferably stem) cell in order to get a mammoth by the classic “Dolly method” - transferring this nucleus into an elephant egg.
It seems that this gun will not fire for ten (maybe fifty) reasons. Firstly, the probability of finding a cell with intact chromosomes in tissues that have lain for 10,000 years in permafrost is virtually zero: they will be destroyed by ice crystals, residual enzyme activity, cosmic rays ... We will analyze some of the other reasons using the example of another, less unrealistic idea.
Simplified genealogical tree of the elephant family
The mammoth genome was read almost completely by an international group of scientists back in 2008. Its chromosomes can be assembled "brick by brick" - to synthesize chains of nucleotides, and not even all six-odd billion, but several thousand pairs of genes (out of about 20,000), which differ from similar sections of DNA of the closest surviving relative of mammoths - the Asian elephant. It remains “only” to read the genome of this elephant, compare it with the mammoth genome, obtain a culture of elephant embryonic cells, replace the necessary genes in their chromosomes - and forward, along the path beaten by Ian Wilmut, leading Dolly the sheep on a string.
A wide variety of animals, from fish to marmosets, have since tilted a multitude. True, cells from donors were taken during life and, if necessary, stored in liquid nitrogen, and less than 1% of the eggs with a transplanted nucleus are obtained from viable newborns. And genes at the same time, if they changed, then one or two, and not thousands. And they transplanted eggs into animals of the same species or very closely related ones, and Indian elephants and mammoths are about the same “relatives” as humans and chimpanzees.
Can a female elephant accept a mammoth embryo, carry it for two years and give birth to a live and healthy baby? Very doubtful. And what will you do with a single mammoth? To maintain the population, even in the “Pleistocene period park”, a herd of at least a hundred heads is needed.
And it is highly desirable that they are not siblings, otherwise the probability of hereditary diseases in their offspring is too high - and the last mammoths died out, among other things, because they could not adapt to the next warming due to too little variability in their genomes. And so on. But if one day it is still possible to clone mammoths, in the north of Yakutia they have long prepared both a table and a house.
Pleistocene park
Several tens of thousands of years ago, on the site of the current tundra, in the same climatic conditions as in our time, there was a tundra-steppe similar to the savanna, in which bison, mammoths, woolly rhinos, cave lions and other living creatures were about the same as now - elephants, rhinos, antelopes, lions and other animals in African reserves. The short northern summer was enough for plants to accumulate enough biomass both for themselves and for feeding herbivores during the polar night.
But during the last large-scale warming, about 10,000 years ago, the animals of the mammoth steppe became extinct (perhaps primitive hunters accelerated this process a little). Plants withered without manure, the ecosystem went haywire, and after a few thousand years the tundra became formless and almost empty.
But in 1980, in a reserve near the city of Chersky at the mouth of the Kolyma, a group of enthusiasts led by the head of the North-Eastern Scientific Station of the Russian Academy of Sciences, Sergei Zimov, began work on recreating the ecosystem of the mammoth steppe by introducing surviving Pleistocene animals into the tundra or their modern analogues capable of existing in arctic climate.
They started with a fenced area of 50 hectares and a small herd of Yakut horses, which soon plucked and trampled almost all the vegetation in this “kraal”, which was too small for them. But that was only the beginning. Now (so far - on a slightly larger area, 160 hectares), elk, reindeer, musk oxen, deer and bison have already been added to horses.
modest achievements
The last of the Tasmanian marsupial wolves exterminated by dingoes, natives and, finally, European sheep breeders - thylacines (Thylacinus cynocephalus) died at the zoo in 1936. In 2008, researchers from the University of Melbourne isolated one of the regulatory genes that enhance protein synthesis of another gene, which is responsible for the development of cartilage and bones, from the alcoholized tissues of museum samples of thylacine, and replaced it with a similar regulator gene in mouse eggs. In two-week-old mouse embryos (potential freaks were not allowed to be born), not a mouse, but a thylacine Col2A1 protein was synthesized. But the revival of the marsupial wolf on a mouse basis is not even worth dreaming of - this is just a genetic trick, the results of which may someday be useful, for example, to study the functions of the genes of extinct species.
In the same Australia this spring, bioengineers from the University of New South Wales tried to grow the frog Rheobatrachus silus, which had died out only 30 years ago, a small animal, curious in that its females bore caviar in their mouths. Scientists introduced nuclei from frozen tissues of R. silus into the eggs of the frog species closest to it, Mixophyes fasciolatus, and even waited for several egg divisions, and after that the embryos died. But the trouble is the beginning, although for the public this amphibious trifle is not at all like dinosaurs.
The experiment of researchers from the University of Zaragoza to clone the Pyrenean ibex, the last representative of which died in 2000, also ended in failure, although much less. The first two attempts to achieve the birth of kids from embryos obtained from the nuclei of cells frozen during the life of the last individual, and the eggs of a domestic goat, ended in miscarriages at best. For the third time (in 2009), Spanish scientists created 439 chimeric embryos, 57 of which began to divide and were implanted in the uterus of surrogate mothers. Unfortunately, out of seven pregnant goats, only one made it to birth, and the goat died a few minutes after birth due to breathing problems.
True, bison are inhabitants of broad-leaved forests, and if they fail to adapt in the Arctic, they are planned to be replaced by a more suitable species - wood bison. We just have to wait until their small herd, sent by colleagues from the reserves of northern Canada and determined to stay in a nursery in the south of Yakutia, increases.
When (and if) instead of a large park, the project receives an area sufficient to organize a reserve, it will be possible to release wolves and bears from enclosures and even try to introduce Amur tigers - the most suitable replacement for cave lions available. What about mammoths? And mammoths - then. If possible.
Are you flying doves?
The American Passenger Pigeon (Ectopistes migratorius) project has nothing to do with ecology. On the contrary, back in the early 19th century, in eastern North America, passenger pigeons flew in flocks of hundreds of millions of birds, eating forests like locusts, and leaving behind an inch layer of droppings, arranged colonies of hundreds of nests on trees, and, despite all the efforts of predators, Indians, and then the first white settlers, did not decrease in number.
But with the advent of the railroads, hunting passenger pigeons became a profitable business. Shoot without looking at the cloud flying over the farm, or pick up the chicks like apples, and hand over to the fence - a bunch for a patch, but bunches - how many you carry. In just a quarter of a century, a few thousand of the billions of passenger pigeons remained - too few to restore the population of these collectivists, even if it had occurred to someone at that time. The last passenger dove died at the zoo in 1914.
The young American geneticist Ben Novak ignited the dream of reviving the passenger pigeon. He even managed to get funding for his idea from the Revive and Restore Foundation (“Revive and Restore”), one of the branches of the Long Now organization founded by the writer Stuart Brand, which supports extravagant, but not too crazy projects in various fields of science.
As material for rearranging the genes, Ben plans to use the eggs of the striped-tailed pigeon - the species most related to the wandering pigeon. True, they are separated from a common ancestor by 30 million years and much more than between mammoths and elephants, the number of mutations. And the experience with replacing genes in bird embryos has been more or less worked out only on chickens, and so far no one has dealt with pigeons ...
But the passenger pigeon's genome has already been read from a tissue sample provided by a museum, and in March 2013 Novak began work on reconstructing the extinct bird at the University of California, Santa Cruz. True, even if the project ends in success, its results will live on in zoos: in nature, passenger pigeons can exist only as part of multi-million flocks. What awaits the "corn belt" of the United States if these flocks can adapt to new living conditions?
Although, even if passenger pigeons cannot be recreated, the results will be useful for attempts to revive dodos (funny Dodo birds), New Zealand moas, Madagascan epiornis similar to them, and other recently extinct bird species.
In January 2013, incredible news spread around the world media: the famous geneticist George Church from Harvard University is looking for a brave woman to be a surrogate mother for Neanderthal cloning. A day later, all decent publications that took this bait published a refutation: it turned out that the journalists from the Daily Mail made a slight mistake in translating an interview in the German weekly Spiegel. Church, who had never dealt with the Neanderthal genome, only argued that theoretically it would someday be possible to clone it, but is it necessary?
Kurosaurs: forward, into the past!
Now back to the scientist we started with, Jack Horner of Montana State University, author of How to Build a Dinosaur. True, it will be more likely a Kurosaurus: the project is called Chickenosaurus, and, according to the author, it will take only five years to complete it. To do this, you need to “wake up” the preserved, but not active dinosaur genes in the chicken embryo. It will be possible to start with teeth: Archeopteryx and other first birds had quite good teeth. True, the maximum that researchers working in this area could achieve was 16-day-old chicken embryos with several conical teeth in the front of the beak, but the journey of a thousand miles begins with the first step ...
That's right, in several stages - step by step, gene by gene, protein by protein - Horner plans to grow his Kurosaurs. Remove the fourth finger, turn the wings into paws ... And it will take five to seven years of work and a couple of million dollars for the first stage of the project. True, there is no information that the Kurosaurs project received funding yet. But there will certainly be a philanthropist: it is not so important that they will not be quite real dinosaurs and, for starters, they will be the size of a chicken. But it's beautiful.
Speaking of beauty, the dark coloration and scales of the dinosaurs in Jurassic Park make them scarier, but that's probably not true. Both Horner and many other paleontologists have long held the view that most, if not all, land-dwelling dinosaurs were warm-blooded and covered in brightly colored feathers. Including the Terrible Royal Lizard - Tyrannosaurus rex. Warm-bloodedness is still a controversial issue, but undoubted traces of feathers on the fossilized remains of close relatives of the tyrannosaurus - Yutyrannus huali (translated from Latin-Chinese - "Beautiful tyrant in feathers", weight - almost 1.5 tons, length - 9 m) - recently discovered expedition of Chinese paleontologists. And what if the structure of its primitive feathers up to 15 cm long is more like chicken down, and not like the complex feathers of modern birds? Well, it can't be that they weren't beautifully painted!
And if future mammoths, dodos, dinosaurs and other extinct animals are not quite real, but almost identical to natural ones, who among you will refuse to walk through the park of a period that at first glance is indistinguishable from the Jurassic or Pleistocene?
As for organic material, can dinosaur DNA be extracted from it? Not really. Paleontologists constantly argue about the suitability of organics, but DNA has never been extracted (and apparently never will be able to).
Take, for example, a Tyrannosaurus rex (which is a rex). In 2005, scientists used a weak acid to extract weak and pliable tissues from the remains, including bone cells, red blood cells and blood vessels. However, subsequent studies showed that the find was an ordinary accident. got seriously excited. Additional analysis using radiocarbon and scanning electron microscopy showed that the material for the study was not dinosaur tissue, but bacterial biofilms - colonies of bacteria interconnected by polysaccharides, proteins and DNA. These two things look very similar, but have more in common with plaque than with dinosaur cells.
In any case, these findings were very interesting. Perhaps the most interesting thing we have not yet found. Scientists improved their techniques and, when they got close to the nest of Lufengosaurs, they pulled themselves together. Captivating? Absolutely. organic? Yes. DNA? No.
But what if it's possible?
there is hope
Over the past decade, advances in stem cells, ancient DNA resuscitation, and genome reconstruction have brought the notion of “extinction in reverse” closer to reality. However, how close and what this may mean for the most ancient animals is still unclear.
Using frozen cells, scientists successfully cloned a Pyrenean ibex known as bucardo in 2003, but it died a minute later. For years, Australian researchers have been trying to bring back to life a southern species of mouth-feeding frogs, the last of which died decades ago, but their quest has so far been unsuccessful.
So, stumbling and cursing at every step, scientists give us hope for more ambitious resuscitations: mammoths, passenger pigeons and Yukon horses, which became extinct 70 thousand years ago. This age may confuse you at first, but just imagine: this is one tenth of a percent from the time when the last dinosaur died.
Even if the dinosaur DNA is as old as yesterday's yogurt, numerous ethical and practical considerations will leave only the most insane scientists among the supporters of the dinosaur resurrection idea. How are we going to regulate these processes in general? Who will be doing this? How will dinosaur resurrection affect the Endangered Species Act? What, besides pain and suffering, will failed attempts bring? Suddenly we resuscitate deadly diseases? What if invasive species grow on steroids?
There is certainly growth potential. Like a representation of the wolves in Yellowstone, a "rollback" of recently extinct species could restore balance to disturbed ecosystems. Some believe that humanity is indebted to the animals it has destroyed.
The problem of DNA, so far, is a purely academic issue. It is clear that resurrecting some frozen mammoth from a frozen cage may not arouse much suspicion, but what to do with dinosaurs? The discovery of a Lufengosaurus nest may have brought us closest to Jurassic Park.
Alternatively, you can try to cross an extinct animal with a currently existing one. In 1945, some German breeders claimed they were able to reanimate the aurochs, the long-extinct ancestor of modern cattle, but scientists still do not believe in this event.
In the movie Jurassic Park, a scientist learned how to clone dinosaurs and created a whole amusement park on a desert island where you could see a living ancient animal live. However, the hypothesis about the possibility of cloning dinosaurs from fossil remains, which was so relevant after the release of the film "Jurassic Park", in the end turned out to be untenable.
Australian scientists led by Morten Allentoft and Michael Bunce from Murdoch University (Western Australia) proved that it is impossible to “recreate” a living dinosaur.
The researchers conducted a radiocarbon study of bone tissue taken from the fossilized bones of 158 extinct moa birds. These unique and huge birds lived in New Zealand, but 600 years ago they were completely destroyed by the Maori natives. As a result of research, scientists have found that the amount of DNA in bone tissue decreases over time - every 521 years the number of molecules is reduced by half.
The last DNA molecules disappear from bone tissue after about 6.8 million years. At the same time, the last dinosaurs disappeared from the face of the earth at the end of the Cretaceous period, that is, about 65 million years ago - long before the critical DNA threshold of 6.8 million years, and there were no DNA molecules in the bone tissue of the remains that archaeologists manage to find.
“As a result, we found that the amount of DNA in bone tissue, if it is kept at a temperature of 13.1 degrees Celsius, decreases by half every 521 years,” said team leader Mike Bunce.
“We extrapolated these data to other, higher and lower temperatures and found that if you keep bone tissue at a temperature of minus 5 degrees, then the last DNA molecules will disappear in about 6.8 million years,” he added.
Sufficiently long fragments of the genome can only be found in frozen bones no more than a million years old.
By the way, to date, the most ancient DNA samples have been isolated from the remains of animals and plants found in permafrost. The age of the found remains is about 500 thousand years.
It is worth noting that scientists will conduct further research in this area, since differences in the age of the remains are responsible for only 38.6% of the discrepancies in the degree of DNA destruction. The rate of DNA decay is influenced by many factors, including the storage conditions of the remains after excavations, the chemical composition of the soil, and even the season in which the animal died.
That is, there is a chance that in conditions of eternal ice or underground caves, the half-life of the genetic material will be longer than geneticists suggest.
Is it possible to clone a mammoth?
Scientists from the Yakut North-Eastern Federal University and the Seoul Center for Stem Cell Research have signed an agreement on joint work on mammoth cloning. Scientists will try to revive the ancient animal using the remains of a mammoth found in permafrost. The mammoth is only about 60,000 years old, and thanks to the cold, it is almost completely preserved. A modern Indian elephant was chosen for the experiment, since its genetic code is as close as possible to the DNA of mammoths.
According to approximate forecasts of scientists, the results of the experiment will be known no earlier than in 10–20 years.
The topic of human cloning is developing not so much in a scientific way, but in a social and ethical way, causing disputes on the topic of biological safety, self-identification of the “new person”, the possibility of the appearance of inferior people, also giving rise to religious disputes. At the same time, animal cloning experiments are being carried out and have examples of successful completion.
The world's first clone - a tadpole - was created back in 1952. One of the first successful cloning of a mammal was carried out by Soviet researchers back in 1987. It was an ordinary house mouse.
The most striking milestone in the history of cloning of living beings was the birth of Dolly the sheep - this is the first cloned mammal animal obtained by transplanting the nucleus of a somatic cell into the cytoplasm of an egg cell devoid of its own nucleus. Dolly the sheep was a genetic copy of the donor sheep.
If in natural conditions each organism combines the genetic characteristics of the father and mother, then Dolly had only one genetic "parent" - the prototype sheep. The experiment was set up by Ian Wilmuth and Keith Campbell at the Roslyn Institute in Scotland in 1996 and was a breakthrough in technology.
Later, British and other scientists conducted experiments on the cloning of various mammals, among which were horses, bulls, cats and dogs.
Recently, there have been more and more reports in the media that scientists can easily resurrect dinosaurs that died out 65 million years ago without any difficulty. However, in reality, everything is not as simple as it seems to those who are not familiar with all the intricacies of these studies. Because you can't actually resurrect dinosaurs. But you can recreate it.
There are only two ways to "resurrect" an extinct animal. The first of them was practiced in the twentieth century. Its essence lies in the fact that if the wild ancestor of some domestic animals dies out, then it is possible to restore its external appearance by selectively crossing among themselves representatives of the most primitive breeds descended from this ancestor. It was in this way that back in the 70s of the last century, German biologists managed to "resurrect" the extinct ancestor (more precisely, one of the ancestors) of modern horses - the tarpan ( Equus ferus ferus).
By crossing representatives of several breeds, in whose cells there were tarpan genes (which were exterminated at the beginning of the twentieth century, that is, not so long ago), scientists managed to create a creature whose appearance absolutely exactly corresponded to that of the ancestral form. Subsequently, these tarpans were released into the wild, and now several herds of these animals graze in Germany and Poland. Interestingly, over several generations, their appearance has not changed significantly - which indicates that the "resurrection" was successful, and these animals, apparently, do contain most of the genes of the horse's wild ancestor. However, it is impossible to verify this, since the genetic data bank of the tarpans themselves has not been preserved.
However, this approach is not applicable to dinosaurs - after all, there are no domestic breeds of these reptiles. True, there are descendants of this group, that is, birds, and a detachment of reptiles has been preserved, which is very close to the ancestral form of the "terrible lizards" - crocodiles, however, crossing representatives of these taxa, which are very far from each other in evolutionary terms, will not give anything (and it is purely technically impossible - the difference in genomes is too great).
Another way of "resurrection" is based on the creation of a hybrid embryo (read more about it in the article "What are the dangers of hybrid embryos?"). If the DNA of an extinct animal is preserved in its entirety, then it can be transplanted into the germ cell nucleus of a representative of the closest species, and thus the desired organism can be grown. With birds and reptiles, this is simple - their entire development takes place in the egg, but the embryo of a mammal at a certain stage needs to be transplanted into the body of a surrogate mother, which is a female of the same, closest species (for example, in the case of the "resurrection" of a mammoth, this there will be an Asian elephant). In this way, biologists plan to "resurrect" a mammoth, a woolly rhinoceros, a big-horned deer and some other prehistoric giants, as well as a marsupial wolf exterminated in the 20th century (read more about what it is in the article "Wolves were afraid to go into the forest ..." ), whose DNA is perfectly preserved and, as they say, is waiting in the wings.
However, this number will not work with dinosaurs - scientists do not have a single DNA sample of these giants. The fact is that the last representatives of this group died out about 65 million years ago, and during this time all the bones of these giants managed, as they say, to recrystallize, that is, all organic matter in them was replaced by inorganic substances, so in fact now they are boulders, somewhat similar to the body parts of dinosaurs. Under such conditions, DNA cannot be preserved. In addition, in the Mesozoic era there were no ice sheets and permafrost, so it is not possible to find the corpse of a "terrible lizard" that would have lain in a frozen state for millions of years (as was often the case with mammoths).
So, as you can see, dinosaurs cannot be "resurrected". However, scientists are convinced that they can be created anew. True, these will be completely different dinosaurs that have nothing in common with the giants that actually existed. But at the same time, they are quite complete.
This technique is based on the fact that the genes of early development (homeosis), which control the formation of the first stages of the embryo, are quite conservative structures, and often almost completely preserved in the descendants. That is why the human embryo in the early stages is similar to a fish, then to an amphibian, and only after that it acquires features specific to mammals. Therefore, the birds, of course, still have the homeotic genes of dinosaurs. In the process of embryo formation, they even work, but for a very short time - then special proteins “turn them off” in order to start the work of homeotic genes specific only to birds.
But what if there was some way to prevent these dinosaur gene shutdowns? Scientists from McGill University (USA), led by Hans Larsson, found that at an early stage in the development of a chicken embryo, the embryo has a reptilian tail. But then, at a certain point, the work of the genes responsible for its formation ends, and the tail disappears. Dr. Larsson and his colleagues tried several times to block the activity of proteins that turn off tail genes. In the end, they managed to do this, but the "tailed" chicken soon died, so plainly and not formed.
Ontogeneticists John Fallon and Matt Harris from the University of Wisconsin (USA) took a different path. While experimenting with mutant chicken embryos, they noticed that some of them have strange outgrowths on the jaws of the embryo. These "bumps" upon closer inspection turned out to be saber-shaped teeth that were identical to the teeth of alligator embryos and, most interestingly, some small Jurassic dinosaurs.
Later it turned out that these mutants had a recessive gene that normally kills the fetus before birth. However, as a side effect of its activity, this gene includes another, which is the homeotic gene of dinosaurs, responsible for the formation of teeth. Interested in this phenomenon, Fallon and Harris created a virus that behaved like a recessive gene, but was not lethal to the embryo. When it was injected into normal fetuses, teeth began to grow, and no harmful side effects were observed. However, the "nibbler" was not allowed to hatch - according to US law, hybrid embryos must be destroyed 14 days after the completion of the experiment.
However, the greatest success was achieved by Dr. Arkhat Abzhanov from Harvard University. He calculated which of the homeotic dinosaur genes are responsible for the formation of a typical reptilian snout instead of a bird's beak. He was also able to identify proteins that "turn off" these genes.
After that, Abzhanov added other proteins to the cells of the embryo that blocked the activity of the "switches", as a result of which the latter stopped working. As a result, there was no one to turn off the dinosaur genes, and the chicken grew quite a pretty muzzle, somewhat reminiscent of a crocodile. At the same time, the embryo itself did not die - it continued to actively develop. However, after 14 days, it was necessary, to the great annoyance of Abzhanov, to kill him too.
All of these studies suggest that creating dinosaurs from birds is fundamentally possible. True, biologists still do not know all the homeotic genes left in birds from dinosaurs, but it is not so difficult to establish this - after all, there is a "control" group, that is, crocodiles. All the subtleties of their work have not been studied to the end, however, this is just a matter of time. So it is possible that in the near future, geneticists will still be able to turn a bird into a small feathered dinosaur from the genus Maniraptor, like those that existed in the mid-Jurassic period.
It should be noted right away that this creature, of course, will not be a representative of a species that has already lived on our planet - after all, its genome will include avian DNA, which was absent from classical dinosaurs. It will be a representative of a new species, created by people, but having the structure and physiology characteristic of real dinosaurs.