This might shock you, but Earth is in the midst of a mass extinction right now – and it’s all thanks to us meddling humans! In fact, more than one in five species on the planet today faces extinction, and that’s predicted to rise to 50% by the end of the century unless we do something about it. However, extinction might not be as permanent as we think. Thanks to the wonders of science, we might even be able to turn back the hands of time by reviving some long-lost species. Let's investigate some extinct animals that might walk the Earth once more!
The Woolly Mammoth
Although they were once thought to have vanished during the last ice age, a recent discovery has revealed that the last isolated colony of around 500-1000 woolly mammoths actually lived on Wrangel Island in the Artic Ocean as recently as 4,000 years ago!
Unlike the elephants we know today, which populate habitats like the savannas of Africa and Asian jungles, woolly mammoths could be found in the tundra, which stretched across northern Asia, many parts of Europe and the northern part of North America. Their smaller ears, shorter tails and extra-thick coats protected them from frost-bite and made them well-adapted to these chilly conditions there.
In fact, the woolly mammoth played such an integral role in the upkeep of this environment that it has also been nicknamed the mammoth steppe! Many scientists think the woolly mammoths died off when the weather became warmer and their food supply changed, although, unsurprisingly, it also seems like pesky humans and their habit for over-hunting may have had something to do with it! But could we be seeing the woolly mammoth again sometime soon? The possibility is more likely than you’d think. Over the years, a handful of well-preserved woolly mammoth specimens have been found frozen in Siberian permafrost, and these could now be key to reviving the long-dead species. It might sound like something from a sci-fi movie, but scientists are hopeful that we might soon see animals we once considered extinct return through something they like to call “
de-extinction”.
The possibility of resurrecting species through de-extinction has become more and more likely thanks to advances in the fields of selective breeding, genetics and reproductive cloning technologies. In the latter part of the 20th century, tools emerged that allowed scientists to isolate and analyze DNA from the bones, hair and other tissue of dead animals like frozen mammoths.
At the forefront of these advances is a handy tool for genetic modification known as CRISPR-cas9, which can be used to isolate specific traits of mammoth DNA that could then be integrated into another animals DNA, like a super-sciency "cut and paste" tool! This could come in particularly useful for bringing back the woolly mammoth because their closest relative is still living: the Asian Elephant. Once the relevant genes have been swapped from the extinct species into the living one, the hybrid genome would be implanted into a surrogate, or could even be grown ex-vitro, outside the mother, using an artificial womb.
This approach doesn’t produce genetically identical copies of extinct animals, but rather modern versions of an animal engineered to look and behave like its extinct relative. So, the end result would be a sort of "mammophant" well-adapted to the conditions of the far north with shorter ears and a thick hairy coat, rather than a bona-fide woolly mammoth! But why should we bring the woolly mammoth back in the first place? Well, it could actually have some major environmental benefits. According to George Church, the researcher heading up the Harvard Woolly Mammoth Revival Team, bringing back the giants could help convert the Arctic tundra back to grasslands that existed during the last ice age. Mammoths and other large herbivores trampling across the ancient Arctic ecosystems helped maintain the grasslands by knocking down trees and spreading grass seeds in their dung.
But when these animals vanished, the ecosystem transitioned into the mossy tundra and taiga we see today, with permafrost that is starting to melt, gradually releasing harmful carbon dioxide into the atmosphere! Russian geophysicist Sergey Zimov has already carried out extensive research proving that tundra can be converted back to grasslands with the re-introduction of grazing animals. With a mammoth herd taking part in something like this, the results could indeed be astounding.
But how close are we to bringing the woolly mammoth back? In 2017, Church said that we could see live woolly mammoths “in a couple of years”, while Dr Tom Ellis, who’s leading research into synthetic biology and genome engineering at Imperial College London, thinks it’ll take at least 10 years. But things are advancing every year. In 2019, top-end scientists in Japan made a breakthrough when cells recovered from a 28,000-year-old preserved mammoth showed signs of life. So, at this point, it certainly feels like a questions of “when”, not “if” we will see these giants walk among us again!
Thylacine
All this talk of de-extinction might be exciting, but we’re still many steps away from re-creating Jurassic Park. Because these new-fangled revival techniques mostly rely on the analysis of DNA that can be recovered from well-preserved specimens, de-extinction does not extend to dinosaurs yet, partly because of the extreme old-age of specimens and the severe degradation of DNA over time.
For that reason, we’re most likely to see species revived that went extinct far more recently: like the Thylacine, also known as the Tasmanian Tiger. This was a large, sandy-colored creature with distinctive dark stripes along its back, with the head of a wolf and a long, stiff tail.
The Thylacine was native to the Australian mainland, Tasmania and New Guinea. It’s thought to have become extinct on mainland Australia some 3,000 years ago, but survived on the southern island of Tasmania until the 20th century. Because the thylacine was a keystone predator, they were accused of sheep-killing and government-sponsored bounties were applied, which ultimately helped to eradicate the species. The last known thylacine in existence was a male specimen who was taken to Australia’s Hobart Zoo, where it died on September 7th, 1939. As if practically killing off the entire species wasn’t enough, this thylacine is also said to have died of neglect. Having been locked out of his sheltered sleeping quarters, he was exposed to a rare occurrence of extreme Tasmanian weather: extreme heat during the day, and freezing temperatures at night. And with that, the thylacine was wiped out for good. But that could all be about to change!
About 750 thylacine specimens are held in museums, and most are pelts or bones with little viable DNA. But 13 young were removed from their mothers pouches and preserved in ethanol, and it was announced in 2017 that one of these babies, held in The Melbourne Museum, had provided enough high-quality genetic material for researchers to
sequence the animal’s entire genome.
For those who don’t speak fluent science, a genome is basically an organisms complete set of genetic instructions. Because each genome contains all the information needed to build that organism and allow it to grow and develop, successfully sequencing one basically means that scientists now have the genetic blueprint to resurrect an extinct animal! The Thylacine genome has revealed details about the marsupial’s evolution and its decline towards extinction. This is a crucial step in possible plans to clone the creature. Cloning may sound like sci-fi nonsense, but it’s already proven to be a viable option. In the 1990s, a technique known as somatic cell nuclear transfer or SCNT was used to produce the first mammalian clone, Dolly the Sheep, who was born in 1996 and died in 2003. But to clone an extinct animal, scientists would take a preserved cell and extract the nucleus. They would then swap this nucleus into an egg cell from the animal’s closest living relative and implant the egg into a surrogate host. Long-extinct animals like the woolly mammoth may never be cloned, but it might just work for animals like the thylacine. Mike Archer, a paleontologist from the University of New South Wales, lead a pioneering project that explored Thylacine cloning in the early 2000’s, and in 2013 his team succeeded in cloning the embryos of another extinct species, the gastric brooding frog.
And, in 2008, a team spearheaded by Andrew Pask from the University of Melbourne were the first to take genetic material from an extinct species and make it function inside a living one, by inserting thylacine DNA involved in bone and cartilage development into mouse embryo’s. Cloning a thylacine will be more challenging than Church’s project to resurrect the mammoth using the Asian elephant because there is no equivalent species for the thylacine. But Pask’s work has demonstrated that, what we once considered a ridiculous possibility 20-years-ago, is now becoming increasingly possible. So, when it comes to bringing the Thylacine back: never say never!
The Dodo
“Gone the way of the Dodo” is an all-too-common sigh of remorse uttered when yet another species joins the ever-growing list of recent extinctions. In fact, because of the rapid decline of this species, as well as its reputation for being a few sandwiches short of a picnic, the Dodo bird has become a sort of poster-child for extinction.
This flightless bird wasn’t such a looker either: it was bigger than a turkey, weighing about 50lbs, and had a blue-grey plumage, a big head, tiny, useless wings and stout, yellow legs. The birds lived on the island of Mauritius and were first seen by Portuguese sailors around 1507. They were ultimately driven to extinction in the late 1600s after invasive species out-competed the bird for food and ate its young.
Less than 75 years after sailors colonized its island home, the Dodo bird was completely wiped out. But as we’ve now learned, extinction doesn’t always mean “forever”. There has been talk of
Dodo de-extinction at Revive and Restore, which is an organization focused on the genetic rescue of endangered and extinct species. With the advancements being made to restore the woolly mammoth and other such creatures, the prospect seemed feasible at first, but there was one big problem: Dodo DNA is extremely hard to find. All that remains of the Dodo is a head and foot at Oxford, a foot in the British Museum, a head in Copenhagen, and more-or-less complete skeletons in various museums throughout Europe, the United States and Mauritius. But in 2016, there was a major breakthrough: Beth Shapiro, an evolutionary biologist at the University of California, announced that the whole genome of the extinct Dodo bird had been sequenced using the genome of the Nicobar pigeon, the dodo’s closest living relative, as a template!
What’s more, Mauritius, having lost the majority of its endemic species, is now home to some of the most incredible recovery projects of endangered species in the world. The majority of endemic species are now confined to small, intensely-managed reserves and predator-free satellite islands to protect them from the very thing that wiped out the Dodo: invasive species.
Before humans turned up, the Mauritius was a haven of birds and reptiles, with a few species of bats being the only mammals endemic to the island. If the invasive mammals that have since thrived there were controlled, the Dodo might just stand a chance of survival. Scientists have already been toying with the idea. One approach would involve genetically engineering mammals, so they breed themselves out of existence using a sex-biasing gene. Of course, this is all speculative for now, but it certainly seems like the return of the Dodo could still be imminent.
The Moa
From one flightless bird to another, allow me to introduce you to the Moa: a group of at least 9 species of enormous birds, some measuring up to 12ft tall and weighing in at a colossal 510lb!
These breath-taking creatures became extinct in the late 1600’s following the arrival and proliferation of the Maori people in New Zealand, who saw the Moa as easy hunting targets with plenty of meat on them. At the same time, habitat loss and impacts associated with other introduced species further helped to seal their doom. But, having been gone for well over 700 years, it seems like there might be hope yet for these big old birds. That’s because scientists at Harvard University have been able to assemble the first nearly complete genome for an extinct moa species: the little bush moa.
Turntable of the little bush moa by matlars21
Don’t be fooled by the name, though, the ‘little’ bush moa was hardly small: it stood more than 4.3ft tall and weighed approximately 66lbs, that’s heavier than a husky! The DNA was reconstructed from the toe bone of a single museum specimen in 2018, and it might begin a new chapter in resurrecting these bygone birds.
The team, lead by Harvard’s Alison Cloutier,
utilized high-throughput-sequencing techniques, which allowed them to sequence hundreds of thousands of strands of DNA all at once. In another sister study, they used the little bush moa genome, along with other DNA data, to determine that moa’s are most closely related to kiwis, emus and cassowaries. The fact that all three of these birds are still living opens up a world of possibilities. Resurrection of the moa would require a little more genetic tinkering of the DNA extracted from the museum specimen and an egg from a living species that the genome could be implanted into. Thankfully, the 6-inch-long, 1lb eggs that emus lay might be just the ticket!
But this step has proven harder in birds than it is with mammals. A reconstructed genome can be introduced into a mammalian egg with the cloning technique that created Dolly the Sheep, but that doesn’t work in birds yet. One hope is to get a workaround that recently succeeded in chickens, which involves putting the genome into embryo cells that become eggs or sperm, to succeed in wild birds. So, the moa might remain in the land of the dead for now, but it’s safe to say we shouldn’t count them out just yet!
Siberian Unicorn
Unicorns once walked among us. Not the graceful creatures from children’s books, it was a totally different beast instead: the Siberian Unicorn.
Besides the enormous horn on its nose, this creature, which roamed the glasslands of Eurasia, shares very few similarities with its fictional counterpart. Instead, the Siberian Unicorn weighed in at a mighty four tons and looked more like a giant, hairy rhinoceros.
Over the years, a few fragmented Siberian Unicorn bones have been recovered, and those have been difficult to analyze. For example, skull found in Kazakhstan in 2016 was said to be radiocarbon-dated up to 29,000 years ago, but because there was so little collagen the result was considered unreliable.
But in 2018, all that changed when DNA of the mysterious giant was successfully analyzed for the first time. Although the hulking animal was originally thought to have become extinct between 200,000 and 100,000 years ago, radiocarbon-dating of a total of 23 bone specimens by an international team of scientists found the ice age giant in fact survived in Eastern Europe and Central Asia until as recently as 36,000 years ago. That means it roamed the Earth among early modern humans! Surprisingly, though,
humans likely had nothing to do with their extinction. Instead, new evidence shows that the hefty beast may have eventually died out because it was such a picky eater! The Siberian Unicorn was like a glorified, pre-historic lawnmower, plodding along grazing on tough, dry grasses. But during a period of significant climate change, when other grass-eaters switched their diets to herbs, shrubs and any other vegetation they could find, the Siberian Unicorn did not adapt. Instead, it continued grazing on what grass was left, even when encroaching permafrost killed it off.
DNA analysis has also revealed that the Siberian Unicorn was not closely related to modern rhinos, contrary to popular belief, but was a unique lineage that split from the line that led to modern rhinos over 40 million years ago! Scientists now hope that knowing more about the extinction of these animals could help save the remaining rhinos on the planet. There are only five species of rhinoceros alive today, and they are notoriously picky about their habitat.
What we’ve already learned about the extinction of the Siberian Unicorn has proved that you don’t need major climate change to have vegetation responses that can wipe out an entire species, and this was even before human’s restricted animals ranges! Now people are looking at large grassland’s like the plains of Africa with a worrying outlook, and better understanding of the Siberian Unicorn could be the key to preventing history from repeating itself. As it stands, complete Siberian Unicorn specimens have never been recovered. We don’t even know how large its horn was because none have been found, however part of the skull where the horn would have grown has been recovered and has inspired estimates that it may have been up to 1 meter in length! How much more we can learn from these magnificent creatures depends on the amount of DNA can be recovered. If a perfectly-preserved specimen, like the woolly mammoth’s, were found frozen in ice, for example, scientists might be able to successfully sequence the full genome, which would offer the first steps towards their resurrection. So, while we may not be seeing these creatures as soon as some of the other candidates for de-extinction, there’s certainly reasons to look into it!
Passenger Pigeon
We can all agree that the last thing the world needs is more pigeons! But you might be surprised to learn that one of the prime candidates for de-extinction is exactly that: the passenger pigeon. This was a small, grey bird with a pinkish-red breast that was once extremely common in North America but vanished around 1900.
Unlike the pigeons of today, which are generally considered pests, passenger pigeons, whose numbers are estimated to have reached nearly 5 billion at the start of the 19th century, played a dramatic role in shaping the forests they inhabited. Their numbers were so great and their droppings so prevalent and flammable that they destroyed trees and increased forest fires.
That doesn’t sound like much of a positive thing but after the passenger pigeons went extinct, these healthy natural disturbances ceased, white oaks lost their primary mode of seed disposal, and the forests have never been the same since. But why did this functionally unique species vanish? It seems that the reasons for passenger pigeons extinction was humans! People ate passenger pigeons in huge amounts, but they were also hunted and killed because they were perceived as a threat to agriculture. As Europeans migrated across North America, they thinned out and eliminated the large forests that the pigeons depended on. At a time when the pigeons were already dying out, 250,000 birds, the last big flock, were shot on a single day in 1896. That same year, the very last passenger pigeon was observed in the wild in Louisiana. It was also shot. Thankfully, we might be able to make amends with these seed-spreading birds. Passenger pigeons were as essential to the forests they inhabited as woolly mammoths were to the tundra, so
bringing them back could be a major step in restoring their former habitat. Ecologist Ben Novak, the lead researcher working on the passenger pigeon project at Revive & Restore, wants to resurrect the bird using its closest living relative, the band-tailed pigeon.
But determining how many genes need to be swapped is a daunting task. The genomes of the two birds are around 97% the same, but that remaining 3% has been built up over millions of years and will take some figuring out. Even then, it’s a matter of getting the hybrid cell to grow in a surrogate, hoping all the genes work harmoniously together, bringing the bird to term and hoping it acts like the extinct species, even though it was raised by a modern relative. Still, Novak is hopeful. If his team secures enough funding, he says that there’s no reason that we can’t have the first generation of passenger pigeons within this decade. So keep your eyes on the skies!
Sabretooth Tiger
If you’ve watched the Ice Age movies, you know what a sabretooth tiger looks like, except, they were probably a lot scarier in real-life. After all, these fearsome predators were named for the pair of elongated teeth protruding from its upper jaw, which reached a staggering 11inches in length!
These big-cats roamed North and South America during the Pleistocene Epoch, and went extinct approximately 10,000 years ago; likely as a combined result of environmental change, decline in prey population and, of course, human intervention. Despite its intimidating size, clocking in at around 5feet long and up to 620lbs, and extremely sharp canine teeth, the extinction of the sabretooth tiger also happened to align with the period when humans started to make huge strides in hunting technology. Although they may not have hunted them for food, they may have killed them for sport using simple projectile weapons. Over the years, scientists have uncovered a number of sabretooth skeletons and fossils in places like the La Brea tar pits of North America, which have revealed additional details about this impressive creature. We know that they were large cats that had short limbs, and scientists now believe they may have been similar in size to a modern-day African lion.
Despite the name, they actually weren’t actually related to modern-day tigers found in Asia. In fact, it has been suggested that their closest living relative is actually the clouded leopard, which are the only modern carnivores with skull features that even approach sabretooth proportions!
Considering sabretooths existed at the same time as woolly mammoths, and would even have eaten the occasional small mammoth, resurrecting these predators isn’t out of the question. If more complete and well-preserved specimens are found frozen in the Siberian permafrost, these could allow scientists to extract DNA and successfully sequence the genome needed to revive the species.
Of course, the next step would be to determine which living relative could act as a successful surrogate for the hybrid genome. But there’s one big question:
are there any benefits to brining back these ice-age predators? As it stands, de-extinction has more to do with ecology than tourism. After all, it would be morally wrong to revive a species that is going to be a zoo animal forever, or a new, more dangerous predator that could threaten existing species. Whether the world is ready to see the sabretooth tiger again remains to be seen for now, but, as we’ve learned, extinction is not always the end. If you were amazed at these animals that scientists are close to reviving, you might want to read about animals that could
come back from extinction. Thanks for reading!
