by Caitlin Andrews
As humans, we have a constant curiosity to know what life on an earlier Earth might have looked like. We use fossils, skeletons, and our own imaginings to reconstruct images of dinosaurs, woolly mammoths, and other prehistoric creatures. We visit museums to come “face-to-face” with these animals and pay tribute to species that were driven to extinction by our ancestors’ actions. All the while, we wonder what it would be like if these animals still roamed the planet.
Scientists estimate that 99% of the roughly 4 billion species to ever live on Earth have gone extinct (1). But, although we often hear extinction being associated with human action, most of these events have been a natural part of Earth’s evolutionary history. Since the dawn of life, extinction has represented the constant ebb and flow as species have fought and dominated or struggled and fizzled out. At five points in time, this process has been drastically accelerated by geological disasters or other events, leading to periods of “mass extinction” in which over 75% of Earth’s biodiversity has been lost. As deforestation, poaching, and climate change impact nearly every ecosystem, there is strong evidence to suggest that we are now in another of those periods—a sixth mass extinction (1). Instead of a more natural pace of one to five species per year, we are losing dozens of species every day. Until recently, these losses were assumed to be permanent (2). But, what if we could somehow reverse the clocks and bring these animals back to life? Would we want to do it? Should we do it? And what would our decision mean for our planet?
THE LAST BUCARDO: The Technology of De-Extinction
While de-extinction, or the process of reviving extinct species, might sound like something out of a science fiction movie, it has already been attempted—and nearly achieved. In the late 1980s, the fate of the Pyrenean ibex, a subspecies of European goat also known as the “bucardo,” looked grim. With only three females left in the wild, attempts to hybridize with a related subspecies failed, and, by 1999, two of the three females had died. With one aging individual left, this species would have been considered doomed by most. But scientists had other ideas. Just months before the last bucardo died and the species was declared extinct, they collected a small skin sample from the remaining individual and preserved it for future use (3).
With this small sample, scientists ensured that the bucardo’s genetic code lived on even as the species did not. Like all cells in the body, skin cells contain an individual’s entire genome; scientists are able to obtain nearly all of the raw material needed to clone a new animal by isolating the DNA-containing nucleus from one of these cells. In 2003, three years after the death of the last bucardo, scientists did just that. They inserted the nucleus into the egg of a domestic goat—whose own nucleus had been removed—and, through in vitro fertilization, implanted a bucardo embryo into a female Spanish ibex-goat hybrid. Of the seven female surrogates who successfully carried a bucardo embryo, this female was the only one to carry the bucardo to term. But, tragically, only ten minutes after birth, the infant female bucardo died from respiratory failure—a fairly common occurrence in cloned animals (3).
Would we consider this infant’s short life to be a true de-extinction event? Although most call it the greatest attempt at de-extinction ever made, there was likely little chance that the species could have been successfully revived even if the bucardo had survived. The Long Now Foundation, an organization determined to bring extinct species back from the dead, uses several criteria to identify viable de-extinction candidates. From how practical it would be to generate enough genetic variation to sustain a healthy population to how much the species’ original habitat has been changed since its extinction, these criteria highlight the main goal of de-extinction: to actually restore a wild population, and not just an individual or two (4). While the bucardo seemed a viable candidate based on these criteria, the technology may have been too new to successfully reintroduce the animals to the European mountainsides.
THE “WOOLLY ELEPHANT”: Alternate Revival Technologies and the Ethics of De-Extinction
The case of the bucardo showed that de-extinction could give recently-extinct species a second chance at life. But, what about species that have been extinct for longer periods of time? Fossils and museum specimens can hold viable DNA for hundreds of thousands of years, so, while dinosaurs are too far gone to be revived, bringing back dodo birds, woolly mammoths, and saber-toothed tigers is not out of the question. However, older specimens are unlikely to yield the pure, intact DNA samples that scientists need to carry out successful cloning. Instead, we would need to use other technologies in order to bring these species back (5).
The Long Now Foundation considers the woolly mammoth to be one of the prime candidates for de-extinction; not only does it meet the criteria for being “iconic” and “beloved,” but there are many well-preserved specimens available for DNA extraction (4). Unfortunately, because these specimens provide only a partially-complete picture of the woolly mammoth’s genome, cloning is not a practical option. Instead, scientists have considered hybridizing woolly mammoth DNA with DNA of the mammoth’s closest living relative—the elephant. Similarly, they could also reverse engineer elephants; through careful and tedious selective breeding and genetic modification, this process could eventually yield animals which, though technically derived from elephants, resemble and even act like woolly mammoths (6).
The woolly mammoth highlights the ethical debate at the heart of de-extinction—why bring back extinct species in the first place? The woolly mammoth was hunted to extinction 4,000 years ago, and the species that were left behind on the tundra have since adapted to the loss (7). However, proponents of de-extinction say that it is our duty to revive species that were driven to extinction by humans. Not only would having real, live woolly mammoths teach us more about their behavior and ecology, but who knows what other knowledge could be gained from these creatures? By learning about how they went extinct, we might be able to learn how to most effectively conserve their nearest relatives and other species. Perhaps most importantly, bringing back mammoths could help reverse the trend of biodiversity loss from which our planet is so greatly suffering. With so many species going extinct, why wouldn’t we bring one back if we could? (8)
While there are many who see the positives of de-extinction, there are those who think that the complications would outweigh any potential benefits. In the case of animals like the woolly mammoth, which have been extinct for thousands of years, there is no doubt that their habitat has changed dramatically since their extinction; in some cases, extinct animals might not even have a habitat to return to, as land development and deforestation have leveled countless ecosystems. Could scientists simply place woolly mammoths back on the tundra and expect them to survive, or would the ecosystem have to be reconstructed exactly as it was thousands of years ago in order to support the mammoth again? Considering the realities of global warming, these animals, if brought back, would have to keep up with the pace of climate change. Additionally, the factors that caused them to go extinct in the first place may be waiting for them when they return. Woolly mammoths were hunted to extinction in the first place, so we might not be able to guarantee that they wouldn’t go down that exact same road again (9).
In response to these criticisms, some proponents claim that bringing back extinct species could actually help reverse climate change. Woolly mammoths, as just one example, could help the tundra by eating dead grass and promoting new growth, as well as by stomping through the snow and letting cold air refreeze the soil (7). Despite these possible benefits, some people still question the motivations behind de-extinction, wondering if it is fair to bring back extinct animals who may have as much of a chance of going extinct again as they did originally. Additionally, selectively breeding mammoth-like traits into the elephant species doesn’t actually recreate woolly mammoths but creates a mere mammoth look-alike—a “woolly elephant” of sorts (9). So, we are left asking ourselves: does de-extinction even achieve its intended goal?
THE TASMANIAN DEVIL: Implications for Conservation
Given the possibility to make extinction a reversible phenomenon, one might think that conservationists would be among the greatest proponents of de-extinction. And, in some cases, they are. The same cloning techniques that are used in de-extinction could also be used to help species that are teetering on the brink of extinction, and there is perhaps no better example of cloning’s potential than the Tasmanian devil. These incredible Australian marsupials are severely endangered due to a deadly, transmissible cancer which has devastated the wild population. While veterinarians and zoologists have struggled to find a cure, cloning could prove invaluable in halting the cancer’s spread. Just as in de-extinction, Tasmanian devil cells could be cloned following genetic modification to remove the single gene that causes the deadly cancer; once these cancer-free individuals are introduced into the wild, they could spread the improved genes throughout the population until all individuals are immune. Considering how much trouble the Tasmanian devil cancer has caused scientists, cloning seems like a simple—and perhaps necessary—solution (8).
De-extinction could also bring extra funding to conservation efforts. Imagine how easily zoos—which are often great financial supporters of conservation—could draw in the public if they were the only places on Earth where you could see living passenger pigeons, giant sloths, and, perhaps someday, Tasmanian devils. This would not only provide zoos with a way of educating the public about conservation issues, but it would also bring in money that could then be used to help conserve other species (8).
But, in other cases, conservationists fear that cloning and de-extinction could spell disaster for some endangered species, even as it saves others. If all of our resources are spent bringing back extinct species—or even saving species that many would consider destined for extinction, like the Tasmanian devil—there are those who fear that currently-threatened species will be forgotten. And, if it were that easy to revive an extinct species, people might be less motivated to protect the planet and prevent extinctions in the first place (10). De-extinction may help increase biodiversity, but it will not prevent a sixth mass extinction unless we address the underlying problems that our planet faces (11).
THE MOA: De-Extinction and the Future of Science
In 1839, Richard Owen, a British professor, purchased a fragment of a femur bone that had been recovered from a river in New Zealand. Despite the seller’s claims that it was from an eagle, Owen had his doubts. As a professor of comparative anatomy and physiology, he knew bones, and he was convinced that this could not have been the bone of a winged animal. But, after tirelessly comparing the bone’s structure and composition with countless museum specimens, Owen had no choice but to admit his error. The femur was, indeed, from a bird, but it was a bird nearly beyond imagination—at least the size of an ostrich. Three years later, Owen stood with one hand grasping the original femur bone and the other resting on the back of a looming, towering figure: the completed skeleton of the bird (12, 13).
Owen would come to be known as one of Darwin’s harshest critics, but the study of the New Zealand moa was his pet project. Reconstructing the creature, bone by bone, he discovered that the moa, standing at an astounding two meters tall, was the only wingless bird to ever live. Unfortunately for Owen, the moa died off around the year 1400, after the Maori people arrived in New Zealand and began hunting the birds for food. So, the most Owen could have done was admire his carefully-reconstructed skeletons—and do his best to imagine what these amazing creatures might have been like (14).
Three hundred years later, the New Zealand moa is one of the top candidates for de-extinction, given the extensive collections of skeletons which are well-preserved and available for DNA extraction, largely thanks to Owen’s work. From a single bone to a completed skeleton, what Owen did in his time was a significant step in preserving these animals for future generations to enjoy, just as de-extinction could become a vital conservation tool in the near future (4). With our planet facing its most grave crisis yet, now is the time to decide whether de-extinction is something dangerous, extreme, and beyond the rights of human beings—or merely the next step in bringing extinct species back to life.
Sources
1: Barnosky, Anthony, et al. “Has the Earth’s Sixth Mass Extinction Already Arrived?” Nature 471 (2011): n. pag. Web.
2: “The Extinction Crisis.” Center for Biological Diversity. N.p., n.d. Web. 14 Oct. 2013.
3: Folch, J., et al. “First Birth of an Animal from an Extinct Subspecies (Capra Pyrenaica Pyrenaica) by Cloning.” Theriogenology 71.6 (2009): 1026-034. Web.
4: “Revive & Restore.” Long Now Foundation. N.p., n.d. Web. 14 Oct. 2013.
5: Zimmer, Carl. “Your De-Extinction Questions Answered.” National Geographic. N.p., 19 Mar. 2013. Web. 14 Oct. 2013.
6: Switek, Brian. “How to Resurrect Lost Species.” National Geographic. N.p., 10 Mar. 2013. Web. 14 Oct. 2013.
7: Church, George. “De-Extinction Is a Good Idea.” Scientific American. N.p., 26 Aug. 2013. Web. 14 Oct. 2013.
8: Brand, Stewart. “Opinion: The Case for Reviving Extinct Species.” National Geographic. N.p., 11 Mar. 2013. Web. 14 Oct. 2013.
9: Switek, Brian. “Reinventing the Mammoth.” National Geographic. N.p., 19 Mar. 2013. Web. 14 Oct. 2013.
10: Pimm, Stuart. “Opinion: The Case Against Species Revival.” National Geographic. N.p., 12 Mar. 2013. Web. 14 Oct. 2013.
11: Switek, Brian. “The Promise and Pitfalls of Resurrection Ecology.” National Geographic. N.p., 12 Mar. 2013. Web. 14 Oct. 2013.
12: Dawson, Gowan. “On Richard Owen’s Discovery, in 1839, of the Extinct New Zealand Moa from Just a Single Bone.” BRANCH: Britain, Representation and Nineteenth-Century History (n.d.): n. pag. Web. 14 Oct. 2013.
13: Campbell, Hamish. “Fossils – Bird Fossils.” The Encyclopedia of New Zealand. N.p., n.d. Web. 14 Oct. 2013.
14: Roach, John. “Extinct Giant Bird Doomed by Slow Growth, Study Says.” National Geographic. N.p., 15 June 2005. Web. 14 Oct. 2013.
