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The Pursuit of Animal De-extinction

It is a sad fact of the world that species are going extinct at a rapid pace, especially in this modern world that humans conquer and exploit day by day. Whether it is due to natural factors, cataclysms, or human activities, some species along with their whole natural heritage and evolutionary legacy are wiped off the face of the earth, gone forever. Or are they? What if we could bring them back, to resurrect these species and allow them to populate the planet and roam the wilderness once again? It is a sci-fi concept that has gained quite a bit of real momentum in recent years, and has been thrust into the public consciousness with the well-known Jurassic Park series of films. Could we do really this? Should we? It is a complicated and complex topic to be sure, but there can be no mistake that bringing extinct animals back from the dead, a process called “de-extinction,” is a very real scientific pursuit, and is being researched and carried out with various degrees of success, with some of the animal candidates for these projects long gone and currently residing only within the lost sands of time.

The technology to carry out the recreation and cloning of animal species has come a long way over the past couple of decades. The first cloned mammal, Dolly the sheep, was met with great fanfare in 1996, but was based on what is now seen as fairly crude technology consisting of simply emptying out an egg, inserting DNA from another animal’s cells, using a simple electric shock to kick start cell division, and hoping that it would work. Indeed, with the technology of the time most cloned animals were plagued with health problems or died shortly after birth, if they were ever born at all, which most weren’t. However, since then scientists have gained a whole new bag of tricks, with more understanding of the cloning process and more sophisticated, refined methods at their disposal, making the prospect of resurrecting lost species that much closer to our grasp. With the possession of these more advanced tools and armed with this new knowledge, scientists have suggested, tried to, and even succeeded in reviving several extinct animals.

Dolly the sheep

One promising method of bringing back species is the use of cloning and genetic engineering. Among the many candidates for de-extinction, the largest and perhaps most ambitious is the plan to try and resurrect the Woolly Mammoth (Mammuthus primigenius), which resembled a large, hairy elephant and went extinct around 10,000 years ago. Since then, there have been amazingly well-preserved specimens found on the frozen tundra of Siberia and in Alaska, and it is believed that the DNA in some of these carcasses can be utilized to bring these lumbering beasts back. There have been several teams devoted to pursuing this, and although they have not been successful yet, the theory behind how this would be achieved is fairly sound.

Of course ideally a living cell would be the most desirable for such an undertaking, but since the cells themselves would probably be too degraded from millennia under the ice, it is believed that a cell nucleus is the key, as it could potentially have lasted longer. The first proposed step is to retrieve the intact nucleus of a mammoth cell from the frozen tissue of one of these well-preserved specimens. Once this nucleus is obtained it is then to be inserted into the egg of a modern elephant, since the process of cloning any extinct animal ideally uses the genome of living specimens of the closest living relative of the extinct species. It is theorized that the nucleus would then take control of the egg and start forming a mammoth embryo, after which it would be transferred into a surrogate elephant mother. This is all easier said than done, but the premise is not entirely far-fetched, and some scientists believe we could have cloned living mammoths or mammoth hybrids within just a few years.

Another proposed method for bringing back the mammoth is to simply take the DNA of a living elephant and modify it through genetic manipulation. In this case, the mammoth’s DNA is more or less copy and pasted into the genome of extant elephants by way of cell cultures called fibroblasts. These elephants can then be bred with the desired mutations that would essentially transform them into woolly mammoths. Although it sounds like something straight out of a science fiction story, The Mammoths Revivalists Team, at Wyss Institute for Biologically Inspired Engineering, Harvard, claims that they have already made good progress in realizing this plan, although it is unknown if any of this will actually work.

Woolly mammoth

Similar methods are hoped to be used to bring back another species, the passenger pigeon (Ectopistes migratorius). Native to North America, these birds were once so plentiful that they formed vast flocks that literally blotted out the sky, and indeed they are widely considered to have been one of the most abundant birds on the continent, reaching populations of up to 5 billion. In 1813, the great naturalist John James Audubon wrote of the bizarre sight of these birds:

The air was literally filled with Pigeons. The light of noon-day was obscured as by an eclipse, the dung fell in spots, not unlike melting flakes of snow; and the continued buzz of wings had a tendency to lull my senses to repose.

At the time this was probably one of the last animals that anyone would have ever imagined would become extinct, but several factors began to take their toll on the species, including deforestation, loss of breeding grounds, and perhaps most damaging of all the nonstop hunting they faced. The plentiful birds were seen as a cheap source of meat, and often the flocks were followed by droves of people wielding rifles who would blast away at the masses of birds until their dead bodies were falling like rain. All of these factors converged to create a rapid decline in the population between the years of 1870 to 1890, the flocks dwindled, and in 1900 the last wild passenger pigeon was shot and killed by a boy with a BB gun. In 1914, the last passenger pigeon known to exist, a bird named Martha, died at the Cincinnati Zoo, thus showing the shocking cataclysm of a species going from one of the most abundant to being totally gone from the face of the earth. But is it really gone forever?

The last passenger pigeon

Since 2012 there have been efforts to try and bring the passenger pigeon back, but it’s not without its difficulties. The main problem is that there is simply no specimen of the bird that has DNA that is intact enough to be usable for cloning. Because of this, the idea with the passenger pigeon is to collect enough fragments of its DNA from disparate preserved specimens so that they can be combined and put together, sort of like a jigsaw puzzle. When enough of the DNA has been reconstructed in this way, it can be used to doctor and edit the DNA in the cells of the passenger’s closest living relatives, the band-tailed pigeon (Patagioenas fasciata) or the common rock pigeon (Columba livia), to eventually produce the lost species through their eggs. This particular technique of patching together incomplete genomes has been honed to the point where it is seen as holding promise for other species for which there is no remaining intact DNA, such as the Thylacine, also known as the Tasmanian Tiger, or even the prehistoric Saber-toothed tiger.

There are obvious hurdles to using cloning and genetic manipulation to bring dead species back to life. For one there has to be enough viable, undamaged DNA to make it work. Unfortunately for fans of Jurassic Park this is why we will probably never see dinosaurs walking the earth again, because DNA does decay, and once it reaches a certain expiry date, at most tens of thousands of years, it becomes unusable. Then there has to be tissue from which to extract the DNA and enough of it present to be of use, or at least to be able to piece the genome together somewhat. There is also the current necessity to have some extant close relative of the extinct species to provide surrogate cells and mothers, meaning that a lost species with no such remaining relatives is probably beyond hope.

Despite these hurdles, the idea itself is not only plausible, but has already been carried out to some degree of success. In 2003 scientists went about trying to clone an animal called the bucardo (Capra pyrenaica pyrenaica), which is a subspecies of the Iberian ibex native to Pyrenees Mountains of southwest Europe. These majestic animals with their formidable curving horns were steadily hunted down until there were only a few dozen left in the 1980s and by 1999 only a single known specimen was known to exist, a female named Celia that was tagged and monitored until her tragic death under a falling tree in 2000.

With Celia’s death the bucardo was another addition to a long list of species gone forever, but in 2003 a team of researchers from Spain and France began a program to try and bring it back. They were greatly aided in the fact that there was very good quality frozen tissue of the creatures kept from Cecilia and others. Due to this perfectly intact DNA, a team of reproductive physiologists led by a José Folch managed to successfully insert the bucardo DNA into a goat egg that had been emptied of its own genetic material and implant it into a goat surrogate mother. After only one of the many pregnancies they orchestrated came to term, the result was the first ever successful de-extinction, but it was to be short lived, as the newborn kid died 10 minutes after birth due to lung complications. While this re-extinction of a newly de-extinct species was certainly tragic, it did show that the technique has the potential to really work, and has paved the way for other researchers and de-extinctions.

There is another way that has been pursued for de-extinction, and this is the use of “breeding back”, or selectively breeding living species in order to recreate the traits and appearance of an extinct one, a sort of artificial process of natural selection. This has notably already been done on a few species, with one of these being an animal called the quagga. This was a type of zebra native to South Africa that had a distinctive appearance in that it only had stripes on the front half of its body, and which was once found in great numbers in its native range. The species was decimated by hunting and competition with domesticated animals in the wake of Dutch colonization, and the quagga was extinct in the wild by 1878, shortly followed by the death of the last living specimen in 1883 at a zoo in Amsterdam.

In 1987, a program called the Quagga Project was enacted to try and bring the quagga back through selectively breeding Burchell’s zebras, which it was found that the quagga had been a subspecies of. It was thought that the quagga phenotype, or basically its observable physical characteristics or traits, could be recreated in this manner, especially the unique stripe pattern the species displayed. The program was successful in producing animals that look very much like the original extinct subspecies, but it is unclear whether they can be called true quagga as although they appear as such it is not known if their actual DNA matches the original quagga because they are still basically normal zebras on a genetic level, with the quagga genotype still more or less still effectively extinct.

Quagga

Even earlier than this was perhaps one of the earliest efforts towards de-extinction ever, which happened all the way back in the 1920s. In this case the animal was the auroch (Bos primigenius), a type of massive ancient cattle that were the ancestors of the domestic cows we know today and were found throughout Europe, Asia, and North Africa. Aurochs became extinct in 1627 due to rampant over-hunting, loss of habitat, and diseases from domesticated cattle, but in 1921 German zoologists Heinz and Lutz Heck began an intensive crossbreeding program designed to bring back auroch-like traits using breeds of modern cattle that display characteristics such as the dark color, large size, general shape, and massive, uniquely-shaped horns of aurochs.

The program was unfortunately supported by the Nazis, but they succeeded in creating cattle with a decidedly auroch-like phenotype, which they called “Hecks.” However, as with the quagga, these are just cattle bred to look like the auroch, so it is unclear whether this can be called a true de-extinction, as the extinct original genotype and gene pool are still gone. In the end these are just look-alikes, imposters that are not really a part of the true genetic lineage of the extinct species they seek to recreate. Even so, there are still other projects that aim to more closely bring back the true auroch and quagga, for better or worse.

With all of this talk about all of the technology, successes, and theories revolving around the question of whether we can resurrect extinct species, there is inevitably the question of whether we actually should. There are certainly ethical questions and themes that need to be discussed, and the debate has been pretty heated at times. Many people believe that it our moral obligation to bring back species that our activities have directly wiped out, especially since their absence creates a loss of biodiversity and could potentially have severe repercussions for the ecosystem as a whole. This camp believes that there are various benefits to restoring the biodiversity that was lost, and that if we had the power to destroy them we should use our power to bring them back. However, others have pointed out that bringing back these species may actually lead to an eventual loss of diversity by funneling much needed funding away from conservation efforts for extant endangered species. Evolutionary biologist John Wiens has said of this:

There is clearly a terrible urgency to saving threatened species and habitats. As far as I can see, there is little urgency for bringing back extinct ones. Why invest millions of dollars in bringing a handful of species back from the dead, when there are millions still waiting to be discovered, described, and protected?

It is not only the money poured into genetic research for cloning extinct species that draws away from funds that could be used to keep other species from joining them, but also the costs involved with keeping these resurrected animals alive after they are created, as their numbers will be small, they’ll need the same funding to protect as any other endangered species, and more importantly the problems that caused them to go extinct in the first place have often not gone away. In this line of reasoning diverting much needed conservation money to reviving extinct species could lead to even more extinctions in the end. It also instills a sense of complacency in us, the false sense of security of some sort of “re-set” button on the ecology, and ecologist Douglas McCauley has given his thoughts on this thus:

Honestly, the thing that scares me most is that the public absorbs the misimpression that extinction is no longer scary. That the mindset becomes: Deforest, no biggie, we can reforest. If we drive something extinct, no biggie, we can de-extinct it.

Another strike against de-extinction plans, especially for species that have been extinct for a very long time, is that in some cases the ecosystem has changed since they have left, or learned to cope without them. For example, with the woolly mammoth the exact environment and all of the other pieces of their ecology they co-existed with no longer exist. If we were to suddenly reintroduce a herd of woolly mammoths into the Siberian tundra it would not be the same tundra they left. What effect would that have on the current ecosystem and the plants and animals that now inhabit it? Would the woolly mammoth not be in essence a potentially invasive species? Some of these revived species would essentially be aliens, and there is little we can do to predict the impact of that.

This is all a debate that seems to have no real end in sight, yet these are things that need to be seriously considered when moving forward with plans for the de-extinction of any species. The whole thing underlines that our technology is starting to move at a pace surpassing our ability to ethically deal with it. We will likely very soon have the ability to bring species back from the dead whenever we like. We will be able to resurrect the mammoth, the saber-tooth cat, anything we like, if not the dinosaurs. However is any of this a good idea? Just because we can does that mean we should do it? The answer to this remains murky.