De-extinction is the process of bringing back to life an extinct animal species. It’s an idea that’s been around for a while. But it was perhaps fully propelled into the public consciousness by the 1993 film Jurassic Park. In contrast, resurrected dinosaurs remain firmly in the realms of science fiction. The de-extinction of other animals is a much closer horizon. We are currently living through earth’s sixth mass extinction period called the Holocene extinction. This mass extinction closely correlates to human activity through hunting, deforestation, pollution, climate change, and other side effects of human expansion.
De-extinction could be one way of resurrecting lost species and protecting those most at risk today. Recent developments in genome sequencing, genetic engineering, and cloning scientists have resurrected recently extinct species. They have their sights set on those lost further back in time. Scientists estimate that 5 billion species have come and gone off this planet. They are using revolutionary new genetic techniques to try to bring back some of these species.
While it’s normal for species to die out over time because of evolution or a cataclysmic event. Some scientists think the Earth is entering a new age of mass extinction, called the Anthropocene or Holocene extinction, caused by humans. Animals, plants, and insects are dying out at a rate of 1,000 to 10,000 times faster than ever before, with dozens of species going extinct every day. Some scientists estimate that many as 30-50% of all species could be headed towards extinction by the end of the century!
How to bring back extinct animals?
If a mammal lived within the last few thousand years, how would we go about bringing them back? There are three main routes currently being explored in the push to de-extinct animals. And they all have pros and cons.
If we had lots of time and a few acres of land, we could try back breeding. Back breeding is a process where lost traits are bred back into living species. Converting an existing species back into a previous form. Back breeding is like reverse engineering evolution, much in how dog breeders work out particular traits, like body shape or coat color. To understand this method, let’s look at researchers in South Africa to recreate the Quagga.
An extinct subspecies of zebra is Quagga. Quaggas and zebras are pretty similar, but where zebras are covered in stripes. Quaggas only have stripes on the front half of their bodies. They also have brown coloring on their rear. They were common in South Africa until European settlers hunted them into extinction in the late 19th century. It is because zebras are a closely related species to the extinct quagga. They are the starting point of the study.
To begin recreating the quagga, scientists select individual zebras that express the same or very similar traits to the extinct species, such as zebras with fewer stripes on the back half of their bodies or zebras with more brown coloring on their back half. Then once these individual animals have been identified, they are bred together. Any offspring that have inherited the desired traits will be bred again.
They are hopefully producing a new generation that carries a mix of extinct species traits. This process must be repeated until the resulting animal is as close to the extinct species as possible. The back breeding project started over 30 years ago. In that time, it has produced multiple breeding groups of near quaggas. After several generations of selective breeding, the animals aren’t quite the same as the originals. But they do have the half stripes and brown rears of their extinct relatives.
There are some downsides and challenges to back breeding. That means it might not be a suitable approach for every animal. First of all, we’d need a close relative of the extinct species to act as our starting point. For animals extinct many thousands of years ago, this may not be possible. It’s also a long process. The gestation period for a zebra, for example, is 12 months. If we need to repeat the breeding process several times over, it could be years or even decades before a herd of our extinct species is ready. And it’s an imprecise process. However, genome sequencing and in vitro fertilization can help breeders be more selective about what gets passed. There are other options if we don’t have a starter species or don’t have time to breed multiple generations.
Another route to de-extinction is cloning. Clones are exact genetic replicas of another organism and arise all the time in nature. Bacteria clone themselves as a means of reproduction, and identical twins are technically clones of each other. But cloning can also be done in the lab. We’ve cloned lots of animals, including buffalo dogs and camels. So how could scientists use cloning to bring back a long-dead species? The most reliable method is probably SCNT or somatic cell nuclear transfer.
It is the method pioneered by the creators of Dolly the sheep, which is the first cloned mammal. Surprisingly scientists have already attempted this method. It began in 1999 when researchers captured the last surviving Pyrenean ibex, a female named Celia. They obtained skin biopsies and froze the tissue in liquid nitrogen. Then in 2009, those skin cells were used to clone Celia in the first-ever case of actual de-extinction.
- First, the nuclei from the frozen skin cells were removed and injected into donor eggs taken from domestic goats, which had their nuclei removed. By adding some chemicals and a jolt of electricity, the process of embryonic development was started. After a few days of growth in the lab, the embryos were implanted into a surrogate mother, either a Spanish ibex or an ibex goat hybrid.
The resulting fetuses had the same DNA as the extinct animal. From the 208 embryos, the researchers implanted only seven pregnancies resulted, and just one ibex made it to term. It was a huge accomplishment. The first-ever extinct animal was brought back into existence. However, the baby ibex died almost immediately from respiratory failure. Most embryos derived from clones don’t develop properly, and scientists don’t fully know why.
Research suggests that it’s not just one stage of the cloning process causing damage to the resulting embryos. In fact, many if not all states contribute. From moving the nucleus from one cell to another to the use of chemicals to kickstart embryonic development. But scientists are not ready to give up quickly instead of setting their sights on an even loftier goal.
In 2019 a breakthrough in the effort to bring back this incredible animal occurred. When a team in Japan successfully transferred the nucleus from a frozen mammoth cell into the egg of a mouse. The nucleus came from a 28,000-year-old preserved mammoth named Yuka. The goal of the experiment was not to create some mammoth mouse hybrid. It was to see if this ancient DNA had the potential to be re-awakened.
Could the cellular machinery in a mouse egg fix the damaged parts of the mammoth DNA and kick-start the DNA replication necessary for embryonic development? If possible, that would suggest the potential for harvested preserved mammoth DNA to be brought back to life through cloning. And the mouse cell machinery did manage to fix some parts of the damaged DNA.
There were some very early signs of the mechanics that underpin DNA replication. But ultimately, the mouse egg could only do so much. The mammoth DNA was too severely damaged. So it’s nearly impossible to reconstitute it enough actually to bring it back to life. Now cloning a mammoth is still a far-off dream. But research like this adds to the field of knowledge that might get us there one day.
The ideal cloning scenario starts with finding an intact frozen cell. The last Mammoth went extinct nearly 4000 years ago. And permafrost does a decent job of preserving genetic material compared to the tropical island where dodos last nested. So, it’ll be a lot easier to scrounge up material to make a mammoth than a dodo. But most scientists doubt that an animal cell could survive several millennia under the Siberian Tundra.
There is one other approach we could try, and it has elements of back breeding and cloning. A new technology opening up options for de-extinction is genetic engineering, more specifically, CRISPR technology. CRISPR-Cas9 is a type of molecular scissor that can cut DNA at a pre-programmed position. It means strands of DNA can be added, removed, or edited at specific points in the DNA.
Scientists could insert genes from an extinct animal into the DNA of a close relative, creating a hybrid with the phenotype the physical attributes of the extinct species. To do this, we’d first need to sequence the extinct animal genome to work out its entire genetic code. Scientists use tests to work out which genes are linked to the phenotype of the extinct species. If we compare the extinct species genetic code to its closest living relative, we could work out where they differ.
Finally, we could copy and paste the genes we want from the existing animal into the host animal DNA. Researchers at Harvard University are trying to use this CRISPR technology to splice mammoth genes into Asian elephant DNA. But it’s a monumental task. There are around 1.4 million known gene mutations separating mammoths and Asian elephants. And not all of the mutations will relate to the mammoth phenotype. It will take a long while to work out which mammoth genes need to be swapped into elephant DNA to recreate a woolly mammoth. But the idea may be the most promising yet, and one day. We may see the first baby mammoth to live in 10,000 years.
Why is de-extinction important?
There are many reasons why we might want to de-extinct a range of different species. One big motivation for de-extinction is to increase biodiversity. Having a variety of animals, plants, and insects in an ecosystem is essential. All of these different creatures perform different vital roles.
- Predators like wolves and bears keep populations of smaller mammals in check.
- Beavers build dams that slow down rivers to create safe environments for other water-loving animals.
- Pollinators like bees and wasps help plants reproduce.
If one animal dies out, it can cause knock-on effects that destabilize the entire ecosystem. De-extinct animals are essential to managing and maintaining their original ecosystems. It could help return those ecosystems to health. Another reason we might want to bring back lost species is to learn from them. Many of the medicines and technological innovations have been developed from initial discoveries in nature.
Extinct species may hold answers to some of the most puzzling research questions. And de-extinction techniques can also be used in the race to save endangered species. There may be a moral obligation to bring back animals that humans are responsible for eradicating. The extinction rate now is thought to be a thousand times faster than before humans became the planet’s dominant species. And a quarter of all mammals now are at risk of extinction.
Should we de-extinct animals?
Although none of the methods are perfect, they certainly bring us closer to the de-extinction of lost species and protect and reviving endangered animal populations. Before bringing back everything from mammoths to thylacines to dodos, we might want to pause and decide whether we should bring back any lost species at all. As cool as it might be to create a de-extinction Safari park, there are some risks. While reintroducing recently extinct species might prove beneficial to existing ecosystems.
Long dead species could end up doing more harm than good. It is because of the changes those ecosystems have undergone in the intervening period. It could create similar problems when releasing non-native species into new areas. The poisonous Cane toad was introduced to Australia to control the grey-backed cane beetle. The toad quickly spread and pushed out native toad populations.
An extinct species might out-compete one that has developed in its absence. Or the ecosystems that once supported an extinct species might no longer be a suitable home. The Chinese river dolphin was polluted out of the Yangtze river, and things haven’t improved since they wouldn’t survive there today.
Scientists will be able to successfully and reliably bring back lost species, particularly those that have been extinct for thousands of years. They will need to think carefully about whether these are risks they want to take. Every day between 30 and 150 species of animal die out on earth for good. Alongside conservation efforts, de-extinction could be a potential avenue to undo some damage humans have enacted on the planet.
One of the most mysterious and strange animals to ever live on earth was the Thylacine found in Australia, Tasmania, and New Guinea. It was the largest carnivorous marsupial with a body that looks like a cross between a cat and a dog, also known as the Tasmanian tiger. It was wiped from the continent of Australia 3,000 years ago and survived in Tasmania until the 1930s when humans finally hunted it into extinction.
Over recent years there have been many reports of Thylacine sightings in the jungles of Tasmania, giving some hope that a few individuals remain. But these sightings are almost all exaggerated or are cases of mistaken identity. Sadly the thylacine is still very much extinct. But it may not be forever. Geneticists are working to resurrect this enigmatic animal with CRISPR and cloning.
Limitation of de-extinction
However, there are limitations. It won’t be possible to bring back extinct species with current technology relying heavily on DNA and well-preserved tissue. It’s unlikely we’ll be able to de-extinct anything that died out more than 10,000 years ago. It is because DNA doesn’t last that long. When an organism dies, cells break down, exposing DNA in the nucleus to damage by enzymes and microorganisms. It means that in ancient tissue. DNA is either non-existent or only present in tiny amounts. So for better or worse, that rules out the dinosaurs.
In May 2013, Russian researchers found a perfectly preserved Woolly Mammoth carcass frozen in the ice on an island off Siberia. As if it were pulled straight out of a meat locker. The animal’s body still had fresh red muscle tissue and the real prize, liquid blood. The female mammoth had been laying there like Snow White for four thousand to ten thousand years before the Russians came excavating. Scientists have cracked much of the mammoth’s genetic code from preserved hair. But the potential to clone the animals isn’t possible without living cells. And this mammoth is currently being examined for just that. If the scientists don’t find any viable cells in their specimen, there’s more than one way to skin a mammoth.
The concept of bringing extinct species back from the void had titillated scientists long before those crafty velociraptors jiggled doorknobs in Jurassic Park. Scientists recently determined that DNA can remain intact for no more than about 6.8 million years. But dinosaurs haven’t been around for about 65 million years. So you will never have to escape a velociraptor. Instead, the only vanished species that scientists can attempt to revive are those that died relatively recently, within the past few tens of thousands of years.
This is kind of fitting considering that’s the very same timeframe in which humans got serious about hunting and expanding and general domination. Many proponents of de-extinction think that if these species were driven to extinction at the hands of humans, then it’s a moral obligation to restore them. It’s also much harder to de-extinct birds or reptiles compared to mammals. It is because we know so much more about mammalian reproduction compared to birds and reptiles.
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