If we brought back a mammoth and stuck it in a zoo, then we could study how mammoths are different from living elephants and possibly learn something about how animals evolve to become adapted to cold climates. Some scientists who favor de-extinction see this as a reasonable goal, and many nonscientists would be just as happy to see unextinct species in zoos as they would be to see them in safari parks or unmanaged wild habitat. But is bringing a mammoth back to life so that we can look at it and possibly study it enough of a societal gain to justify the costs of creating that mammoth?
If, like elephants, mammoths helped to maintain their own habitat, then bringing mammoths back to life and releasing them into the Arctic may transform the existing tundra into something similar to the steppe tundra of the ice ages. This might create habitat for living and endangered Arctic species, such as wild horses and saiga antelopes, and other extinct megafauna that might be targets for de-extinction, such as short-faced bears. Is the possibility of revitalizing modern habitats in a way that benefits living species enough to justify the expense? Of course, ecosystems change and adapt over time, and there is no certainty that the modern tundra would convert back to the steppe tundra of the Pleistocene even with free-living populations of unextinct mammoths. Should uncertainty of success influence our analysis of the cost of de-extinction?
What if we identified a very recently extinct species that played a similarly important role in a present-day environment, and brought that species back to life? For example, kangaroo rats are native to the deserts of the American Southwest, but their populations have become increasingly fragmented over the last fifty years, and many subspecies are known to be extinct today. Kangaroo rats are so important to their ecosystem that their disappearance can cause a desert plain to turn into arid grassland in less than a decade. The domino effects of kangaroo rat extinction include the disappearance of plants with small seeds and their replacement by plants with larger seeds (on which the kangaroo rat would have fed), in turn leading to a decline in seed-eating birds. The decrease in foraging and burrowing slows plant decomposition and snowmelt, and the lack of burrows leaves many smaller animal and insect species without shelter. When the kangaroo rat goes extinct, the entire ecosystem is in danger of the same. If bringing the kangaroo rat back could save the entire ecosystem, would that be sufficient to justify the expense?
In the chapters that follow, I will walk through the steps of de-extinction. As I indicated earlier, de-extinction is likely to happen in two phases. The first phase includes everything up to the birth of a living organism, and the second will involve the production, rearing, release, and, ultimately, management of populations in the wild. For each step in the process, I will describe what we now know, what we need to know, what we are likely to know soon, and what’s likely to remain unknown. I will discuss both the science and the ethical and legal considerations that are likely to be part of any de-extinction project. Although the book is organized as a how-to manual, de-extinction is not a strictly linear process, and not all steps will apply to every species. Species from which living tissue was cryopreserved prior to their extinction may be clonable in the traditional sense, for example, while other species will require additional steps to create a viable embryo.
As part of my professional relationship with Revive & Restore, I have been involved in research that focuses on two species—mammoths and passenger pigeons—that are presently targets of de-extinction efforts. This will no doubt result in an animal-centric (really mammoth and pigeon-centric) view of the process. Still, many of the details will be broadly applicable across taxonomic lines. My hope is to present a realistic but not cynical view of the prospects for de-extinction, which I believe has the potential to be a powerful new tool in biodiversity conservation.
CHAPTER 2
SELECT A SPECIES
I taught a class on the topic of de-extinction recently for graduate students studying ecology at UC Santa Cruz. For their first assignment, I asked each of the students to choose an extinct species that they’d like to see brought back to life and to become that species’ de-extinction advocate. I was curious to learn not only which species they would choose but also what their motivations for choosing a species would be. Because the students were ecologists, I expected them to focus on the impact of each potential “de-extinctee” on the environment into which it would be released, should de-extinction be successful. They did not.
The students selected, among other species, the Yangtze River dolphin, the dodo, the moa, the Tasmanian tiger, the Cascade Mountains wolf, Steller’s sea cow, and Thismia americana—a tiny, translucent plant that is so poorly described that it lacks a common name. Some of their arguments in favor of de-extinction were purely research-oriented—imagine what could be learned by studying this species—while others were more practical—imagine how this species might create new opportunities for ecotourism. Most students discussed the technical challenges of de-extinction—it would be hard to find well-preserved dodo remains, for example, or a surrogate mother for a Tasmanian tiger. Some students acknowledged that suitable habitat might be hard to find, and that existing laws might make it hard to protect the species once it was released into the wild. Few, however, discussed what effect introducing an unextinct species into an existing community might have, which surprised me.
As the class progressed, it became clear that the students had different motivations for selecting candidate species for de-extinction. Some students wanted to bring a species back simply because it would be exciting to do so. Others chose species that they believed could provide significant ecological and environmental benefits, or that might improve our understanding of the evolutionary processes that lead to diverse forms of life. One student selected the species that he believed had the fewest technical barriers in the way of success.
None of these are “wrong” reasons to choose a species for de-extinction. However, the diversity of motives within this small group highlights the first significant challenge faced by scientists doing on-the-ground de-extinction work: to agree on what to bring back. How do we decide which species should be the first targets of de-extinction? Should we choose the species that will be the easiest to bring back? The most awe-inspiring? The most likely to draw attention, perhaps motivating further investment into the technology? Or should we focus on those species whose de-extinction is clearly scientifically justifiable? And, if the latter, what does that mean exactly? Finally, and just as importantly, who is the “we” that gets to decide?
THE “RIGHT” REASONS FOR DE-EXTINCTION
As I suggest above, there are likely to be many reasons to select (or not to select) a particular species for de-extinction. Whether de-extinction is technically feasible, and whether suitable habitat exists into which a species might be reintroduced are important considerations. These questions address whether a species can be brought back, however, rather than whether it should be brought back. The latter is, unsurprisingly, a much more difficult question to answer.
Let’s consider the Yangtze River dolphin, for example. Bringing back the Yangtze River dolphin would certainly be exciting, which some may feel is sufficient motivation to try. Those who would benefit most from its de-extinction would probably be more likely to advocate for it over other candidate species. But who would those people be? The students offered three substantive arguments in favor of bringing back the Yangtze River dolphin, each highlighting different potential benefits, and therefore beneficiaries, of Yangtze River dolphin de-extinction.
The demise of the Yangtze River dolphin—also known as the baiji—is a terribly sad case. My friend Sam Turvey, who works for the Zoological Society of London, has devoted a big part of his life to looking out for species that are on the brink of extinction. In 2006, he led an expedition to survey the Yangtze River for any signs of river dolphins. Sam and his team searched the Yangtze River system for two months and saw no dolphins or signs of dolphin life. With heavy hearts, they declared the Yangtze River dolphin funct
ionally extinct.
The first of the students’ arguments in support of Yangtze River dolphin de-extinction emphasized the evolutionary distinctiveness of the Yangtze River dolphin. Only two other freshwater dolphin species—the Ganges River dolphin of Southeast Asia and the Amazon River dolphin of South America—are known. When scientists first described the river dolphins, they noticed that the three species looked very much alike. All three river dolphins have long, narrow mouths, for example, with lots of teeth. They also have small eyes, compared with their marine relatives. Scientists decided that these morphological similarities probably meant that the three river dolphin species were descended from a single common ancestor species that was also a river dolphin. When genetic data became available, however, it was clear that this was not true. Instead of confirming a single evolutionary lineage, the genetic data indicated that each species made a separate transition from the ocean to freshwater. The morphological similarities among them arose from a combination of shared, deep ancestry and convergent evolution—life in similar environments led to the emergence of similar traits. This makes each freshwater dolphin species particularly valuable from a scientific perspective. We can compare their genomes, physiologies, and behaviors to better understand how species adapt to freshwater environments. Scientists would be one group to benefit from Yangtze River dolphin de-extinction.
The second of the students’ arguments pointed out that rare things intrigue everyone, and not only scientists. If the Yangtze River dolphin is brought back to life, the spectacle of its existence would likely be sufficient to attract certain types of tourists who would be keen to see the animal firsthand. Ecotourism is one of the most rapidly growing sectors of the tourism industry. It both provides jobs and inspires communities to take advantage of local natural resources. Tourists would come to take photos, sleep in a local hotel, eat at a few local restaurants, and maybe even buy a stuffed toy dolphin replica to take home. Yangtze River dolphin de-extinction would have a positive economic impact. The people who live in the region of reintroduction would benefit, as would tourists—some may even be inspired to care just a little bit more about the plight of the native species back home.
The students’ final argument postulated that Yangtze River dolphins should be brought back because their de-extinction would necessarily have a positive impact on the environment. The Yangtze River is presently too polluted to support dolphins, so this situation would have to change. Bringing back the river dolphin would require making the river ecosystem a cleaner, healthier one, with far-reaching ecological benefits.
This same multi-faceted rationale holds true for other species. For example, another group of animals that my students felt were good candidates for de-extinction were the moa of New Zealand. As with the Yangtze River dolphin, the reasons for bringing back the moa are both scientific—moa have no close living relatives, so understanding their biology and behavior is nearly impossible without bringing them back—and economic—living moa would provide yet another reason for people to visit New Zealand, which is already a popular ecotourism destination. Resurrected moa may also re-establish missing interactions with other species, benefiting the native ecosytems of New Zealand.
Moa were enormous birds that did not fly (figure 1). Some species of moa reached more than three meters tall with their necks outstretched and weighed more than two hundred kilograms. Because they didn’t fly, moa were easy targets for the first inhabitants of New Zealand—the Māori—who hunted them for food, used their bones to make jewelry and fishing gear, and fashioned their skins and feathers into clothing. Māori and moa coexisted on the islands of New Zealand for more than three hundred years before hunting and habitat loss eventually led to the moa’s extinction.
Figure 1. Sir Richard Owen and his reconstruction of a giant moa, Dinornis novazealandiae. In his right hand, Owen holds the first moa bone that he examined. This photograph was first published in Owen’s book, Memoirs on the Extinct Wingless Birds of New Zealand, vol. 2 (London: John van Voorst, 1879). Courtesy of the University of Texas Libraries, The University of Texas at Austin.
In New Zealand, moa are a symbol of national pride. Very briefly in the 1890s, New Zealand was officially dubbed the “Land of the Moa,” thanks in part to a play of the same name written by George Leitch. New Zealanders have created moa artwork, moa poetry, and even moa beer, and many New Zealanders are strongly in favor of bringing moa back to life. New Zealand has a strong record of environmentalism and protection of native species and habitat, which means that unextinct moa would probably be provided with a safe place to live should they be resurrected. However, some of the challenges of de-extinction mean that unextinct moa would probably not be 100 percent identical to the species that once inhabited New Zealand but rather genetic hybrids with nonnative birds. It is not clear how these hybrid animals might be accommodated within the environmental philosophies of many New Zealanders.
A third popular choice among my students was the dodo (figure 2). Dodos were large, flightless pigeons that were endemic to Mauritius, a volcanic island situated in the Indian Ocean about 1,200 miles from the southeastern coast of Africa. In 1507, Portuguese sailors landed on Mauritius, which was at that time uninhabited by people, after being blown off course by a cyclone. The Portuguese were not particularly interested in the island and did not establish a permanent colony. Dutch sailors arrived about ninety years later but didn’t stick around either. They did, however record for the first time a large, fat, flightless bird with little to no fear of humans. In 1638, twenty-five Dutch sailors returned to Mauritius and established the first permanent human settlement. Twenty-four years later, the dodo was extinct. Based on written accounts of the interactions between humans and dodos, humans are clearly to blame for the dodo’s extinction.
Figure 2. Dodo, Raphus cucullatus. Illustration by Adrian van den Venne, probably around 1626.
As with the Yangtze River dolphin and the moa, scientific, ecological, and economic interests can be cited as reasons to resurrect the dodo. The dodo is a large, flightless pigeon whose closest relative is a small, strong flyer. Studying its genome could help scientists to better understand how traits such as flightlessness and gigantism evolve. Reintroducing dodo populations to Mauritius would require the creation of suitable habitat, which would mean removing invasive species and establishing new protected zones, which would benefit both the local people and the native ecosystem. The dodo is a special case for de-extinction, however, because it, more than any other species, is the international symbol of human-caused extinctions. If candidate species were to be ranked according to the potential psychological impact of their de-extinction, the dodo would be very high on the list.
A SHORT GUIDE TO DE-EXTINCTION DECISION MAKING
The three examples above highlight what I have come to understand as a general principle of selecting de-extinctees. Most people are at least somewhat uncomfortable with the idea of de-extinction. However, when forced to come up with one suitable candidate species, nearly everyone chooses something that is extinct because humans made it so. The Yangtze River dolphin is extinct because we destroyed its habitat. Moa are extinct because we hunted them to death. Dodos are extinct because we introduced cats and rats and pigs to Mauritius, and these cats and rats and pigs made easy meals of all the dodo eggs they could find. If it had not been for humans, each of these species would probably still be alive.
In addition to how a species became extinct, other characteristics of species make them more or less popular choices for de-extinction. Perhaps unsurprisingly, most people would prefer to resurrect herbivores, rather than carnivores. Less obviously, most people choose large species for de-extinction rather than small species, presumably because large species are, well, bigger. And most people choose to bring back animals, as opposed to plants, fungi, or any other living thing.
It is enormously important to make an informed rather than emotional decision about whether an extinct species should be brought back to life. Diff
erent species require different technical innovations, different amounts of hands-on manipulation, and different habitat. Some species would be decidedly easier to bring back than others. Some species would proceed relatively straightforwardly through the early steps of de-extinction, such as sequencing their genome, but present potentially insurmountable challenges during later steps, such as identifying suitable habitat into which they could be released. When considering whether a species is a good candidate for de-extinction, it is tempting to focus only on those steps leading to the birth of a newly unextinct animal and to ignore the later steps of rearing and reintroduction into the wild. It is unwise, however, and I would go so far as to say unfair, to proceed through these first steps without careful evaluation of the entire process from fertilized egg to free-living population. What is the point, after all, of bringing a species back from the dead if it is not to reestablish a wild population?
To simplify navigation through the process of selecting a species for de-extinction, I propose seven questions that should be asked and answered. The questions fall into two broad categories. The first set of questions attempts to place that species in the context of its ecosystem. How did it interact with and affect other species when it was alive, and how might that be different today? The second set of questions turns to the nitty-gritty of the science. Is de-extinction of this species—or at least of some specific traits that defined this species—practical, given current and future technologies? My focus for now is on the technical aspects of de-extinction and not the ethical questions that will undoubtedly arise throughout the process. Obviously, these questions are not exhaustive, and not every question applies to every species. These questions do, however, provide a useful means to think through the implications of de-extinction and, perhaps, avoid some potential disasters.
How to Clone a Mammoth Page 3