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Philosophy and ethics of de-extinction

Published online by Cambridge University Press:  30 January 2023

Jay Odenbaugh Open the ORCID record for Jay Odenbaugh [Opens in a new window]
Jay Odenbaugh*
Affiliation:
Department of Philosophy, Lewis & Clark College, Portland, OR, USA
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Author for correspondence: Jay Odenbaugh, Email: [email protected]
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Abstract

In this essay, we explore the philosophical and ethical issues concerning de-extinction. First, we will characterize what de-extinction is. This requires clarification of the process of extinction. Second, we consider whether de-extinction is even possible. There are a variety of arguments involving the nature of species that purport to show that once they have disappeared they cannot be resurrected. Third, we examine whether de-extinction is morally permissible. There are arguments that suggest we are obligated to do it based on restorative justice and biodiversity conservation. There are other arguments that conclude we are not permitted to do so based on considerations of animal welfare, hubris and the allocation of conservation resources.

Keywords

Ethics and policyAncient DNABiodiversity conservationConservationDeextinction
Type
Overview Review
Information
Cambridge Prisms: Extinction , Volume 1 , 2023 , e7
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
Copyright
© The Author(s), 2023. Published by Cambridge University Press

Impact statement

De-extinction is a conceptually and ethically challenging topic. Through careful philosophical reflection, we can recognize it is a logically coherent course of action, though it is not always ethically advisable. Sometimes it is morally impermissible.

What is de-extinction?

Many think that once a species goes extinct, the species ceases to exist. However, recent scientific work on de-extinction suggests the possibility of “resurrecting” lost species. From a philosophical perspective, this raises two questions. First, is de-extinction even possible? Second, should it be done even if we can do it? In this essay, we consider proposed answers to both questions.

To begin, we need to get clearer on what exactly de-extinction is. One problem that immediately appears is that de-extinction seems to be impossible by definition. Here is an example of this worry from Alastair S. Gunn.

To say that a species is extinct is to say something about its past as well as its present status – although there used to be moa, they no longer exist. It may be argued that extinct also says something about the future of a class – that once it becomes a null class, it can never come to have members again. It may even be claimed that this is what extinct means. If so, then the question, “Can extinct species be recreated?” is answered negatively by resort to what is sometimes called “definitional stop.” (Gunn, Reference Gunn1991, p. 299)

If a species is extinct, then it cannot exist in the future. If it cannot exist in the future, then it cannot be resurrected. But de-extinction just is the resurrection of an extinct species. Therefore, de-extinction is impossible. Before I examine this argument, I want to consider a terminological worry. As Beth Shapiro notes, “de-extincted” is an awkward and unappealing verb. I will describe the process of de-extinction as resurrection when we can bring back the very species that disappeared. I will use the term recreation when we create organisms very similar to those of an extinct species but that are not necessarily the same species as it. Resurrection is sometimes associated with bringing back the very organism who has died, and this is not what is being discussed in debates regarding de-extinction. We are discussed higher levels of organization such as populations, species and the like.

To see the error in this argument, we must consider what “extinct” means. The Concise Oxford Dictionary of Ecology defines it this way, “Applied to a taxon no member of which is living at the present time” (Allaby, Reference Allaby1992, p. 150). However, this would imply when plants of a species are dormant, it has gone extinct. Yashina et al. (Reference Yashina, Gubin, Maksimovich, Yashina, Gakhova and Gilichinsky2012) found 30,000-year-old fruit tissue from narrow-leafed campion (Silene stenophylla) in the Siberian permafrost and were able to successfully create fertile plants. Likewise, gene banks such as the Svalbard Global Seed Vault serve as repositories for regenerating species.Footnote 1 Thus, this definition does not capture what extinction is.

A different definition comes from paleobiologist Michael Hannah. He writes, “The extinction of a species occurs when the last individual belonging to that species dies” (Hannah, Reference Hannah2021, p. 36). His definition does not imply that the narrow-leafed campion went extinct when there were no living members. This is because the last member had not died. So, the simplest response to the argument that de-extinction is impossible by definition is that in cases where the resurrection of a species occurs, we were simply wrong that the species had gone extinct. We thought it was extinct, but it was not. This does occur occasionally in other contexts. For example, the black-browed babbler (Malacocincla perspicillata) had not been observed in 170 years and was presumed extinct. However, in 2020, a team of researchers found a specimen in Borneo (Akbar et al., Reference Akbar, Nugroho, Suranto and Fauzan2020).

One might object that this response trivializes the notion of extinction (and thus the impossibility of de-extinction). For any given species, they might be resurrected and so we are never able to declare a species extinct. For example, Ben Novak suggests that we consider “reproductively competent single cells” as members of an “evolutionary torpid species” (Novak, Reference Novak2018, p. 9). However, even in the best of circumstances, information from DNA cannot be extracted after approximately 1.5 million years (Allentoft et al., Reference Allentoft, Collins, Harker, Haile, Oskam, Hale and Bunce2012). Thus, for any species which has disappeared for that length of time or more, we simply cannot resurrect them. In some cases, we can confidently declare a species extinct. The concept of extinction is not trivialized by de-extinction.

Let us characterize what de-extinction is. De-extinction is the process of creating living organisms that are similar (often genetically similar) to members of extinct species (Sandler, Reference Sandler2017, p. 1).Footnote 2 Some authors augment this definition with notions of ecological function. For example, Ben Novak writes,

[D]e-extinction is the ecological replacement of an extinct species by means of purposefully adapting a living organism to serve the ecological function of the extinct species by altering phenotypes through means of various breeding techniques, including artificial selection, back-breeding and precise hybridization facilitated by genome editing. (Novak, Reference Novak2018, p. 5)

These definitions of de-extinction are inclusive. The reason they are inclusive is that the techniques associated with de-extinction do not require that a species be resurrected but also may be recreated.Footnote 3 To see why, let us consider these three techniques (Shapiro, Reference Shapiro2015, Reference Shapiro2017). There is back-breeding, cloning through somatic cell nuclear transfer (SCNT), and genetic engineering. This also allows us to explore examples of current or future de-extinction.

Back-breeding uses selective breeding to bring back ancestral traits in extant populations of organisms.Footnote 4 This technique has been used in bringing back traits in species similar to the auroch (Bos primigenius) which is the ancestor of modern cattle. The last known auroch died in Poland in 1627. Fascinated with the animal, German brothers Heinz and Lutz Heck selected for cattle that had large horns, large body size, and were more aggressive than most cattle. In 1983, a group of 32 “Heck cattle” were released into a nature preserve in the Netherlands, the Oostvaardersplassen.Footnote 5 Notice that back-breeding recreates the auroch by virtue of reestablishing auroch-like traits though the auroch is not resurrected. This is because in recreation we create organisms very similar to those of an extinct species even when they are not members of the same species.

Cloning uses SCNT to create a genetic copy of an organism. The nucleus from an adult somatic cell is placed into an enucleated egg cell. The host egg cell becomes an undifferentiated pluripotent stem cell and has an identical nuclear genome sequence to the donor of the somatic cell.Footnote 6 For example, in 2003, a cloned bucardo (Capra pyrenaica pyrenaica) calf was born. The bucardo is an extinct subspecies of the Pyrenean ibex. This individual died soon after they were born due to a lung deformity. One of the most discussed possibilities for de-extinction is the woolly mammoth (Mammuthus primigenius) which went extinct in Eurasia and North America about 8,000–10,000 years ago. The last population of dwarf woolly mammoths disappeared on Siberia’s Wrangel Island 4,000 years ago (Vartanyan et al., Reference Vartanyan, Arslanov, Tertychnaya and Chernov1995; Stuart et al., Reference Stuart, Kosintsev, Higham and Lister2004). Fortunately, there are many mammoth bones in the subarctic from which cells (or at least chromosomes) could be extracted. Woolly mammoths are more closely related to Asian elephants (Elephas maximus) than African ones (Loxodonta). In principle, they could be cloned with Asian elephant mothers. One serious ethical problem here is that the Asian elephant is endangered, and egg harvesting, implantation along with pregnancy would likely harm them. Of course, some surrogate species are not endangered. We will consider issues of animal welfare later.

For approximately 100,000 years, there was a large area of productive grasslands on which horses, bison, woolly rhinoceroses and woolly mammoths lived. This “mammoth steppe” disappeared 10,000 years ago (Zimov, Reference Zimov2005). Mammoths, and other megafauna, disappeared due to a combination of climate change and human predation. This in turn leads to the disappearance of these grasslands. These grasslands created carbon-rich materials such as dead plant roots frozen in the soil and permafrost. However, anthropogenic climate change is melting the permafrost and this will rot the plant material releasing this carbon (or methane) into the atmosphere. Sergey A. Zimov, founder of Pleistocene Park, proposes resurrecting woolly mammoths to slow down permafrost melting. Snow-covered forests have a lower albedo than do snow-covered grasslands. The recreation of snow-covered grasslands would prevent a greater amount of permafrost melt than currently existing snow-covered forests. Grazing animals would trample the snow which brings colder air to chill the permafrost (this air is often colder than the permafrost itself). Zimov and his colleagues have established herds of herbivores including horses, moose, reindeer, muskox and yak. Unlike woolly mammoths, however, these animals cannot knock down trees to create grassland. Thus, Zimov and his colleagues have been using a tank to bring down the trees. One remarkable proposal then is to resurrect or recreate woolly mammoths to combat anthropogenic climate change.Footnote 7

Genetic engineering uses ancient DNA and genome editing to resurrect or recreate a species. To do this, scientists must first reconstruct the genome of the extinct species. As noted, DNA can often survive much longer than cells after an organism dies. This is especially so with organisms that die in cold environments.Footnote 8 Full genomes have been reconstructed for mammoths, aurochs and passenger pigeons (Ectopistes migratorius).Footnote 9 The next step in resurrecting a species using genetic engineering is to determine what parts of the genome are responsible for which phenotypes. Next one takes the cell with the edited genome and creates a living organism. This often combines genetic engineering with SCNT in groups like mammals. However, genetic engineering currently cannot be used with SCNT in egg-laying species like birds or reptiles. One target for de-extinction using genetic engineering is the passenger pigeon. It is an awe-inspiring species, which existed in the billions. Aldo Leopold called it a “biological storm” (Leopold, Reference Leopold1949, p. 104). One recorded flock was 300 miles long and a mile wide. Martha, the last passenger pigeon, died in 1914 at the Cincinnati Zoo. The cause of the passenger pigeon’s disappearance was predation by humans. For example, in 1878 hunters killed over 50,000 birds per day for 5 months straight.Footnote 10

Currently, Ben Novak along with George Church working with others like Stewart Brand is planning to bring back the passenger pigeon.Footnote 11 The passenger pigeon’s genome has already been sequenced and its closest living relative is the band-tailed pigeon (Patagioenas fasciata). They have already identified which parts of the band-tailed pigeons’ genome that must be edited and replaced via CRISPR with the passenger pigeon’s genes. Thereafter they would grow band-tailed pigeon cells and edit the DNA within the nucleus with synthetic passenger pigeon DNA. As noted above, here complications arise since birds cannot be cloned. A fertilized ovum divides with its yolk moving down the oviduct, which is wrapped in albumen. When it reaches the isthmus, membranes are deposited around it and the eggshell is added. Currently, it is simply too difficult to enucleate and replace the nucleus of the egg without disrupting the process. Instead, primordial germ cell transplantation (PGCT) is used to create a chimera between the passenger and band-tailed pigeons. When PGCT is used where the donor and recipient are of distinct species, we have interspecies PGCT or iPGCT. From here, adult chimeras are mated together and scientists will work to establish a population of these birds.

A caveat of some importance is that these techniques for recreating or resurrecting species do not create an organism that is a copy of an extinct one. With back-breeding, at best an organism with the same phenotype of an extinct one is created. With genetic engineering, at best the same phenotype is generated from some of the same genes as the extinct organism, but many other parts of the genome are different (Sherkow and Greely, Reference Sherkow and Greely2013). Even organisms that are cloned from extinct ones using SCNT are not copies since the mitochondria of the two will be different. Finally, there are different gene–environment interactions that occur with respect to the resurrected organisms and the extinct ones that can change their respective developments. However, many proponents of de-extinction suggest that creating exact copies of extinct species is not the primary aim. Beth Shapiro writes,

In the majority of ongoing de-extinction projects, the goal is to create functional equivalents of species that once existed: ecological proxies that are capable of filling the extinct species’ ecological niche. (Shapiro, Reference Shapiro2017, p. 6)

Whether this is the aim of de-extinction research or not, can we nevertheless resurrect species?

Is de-extinction possible?

Philosophers have argued about whether de-extinction is even possible. This issue is not whether it is difficult or even unlikely that a species will be resurrected or recreated. The concern is that it is physically or conceptually impossible.Footnote 12 On some views of what species are, they contend it is not possible (and possible on others) (Siipi and Finkelman, Reference Siipi and Finkelman2017; Finkelman, Reference Finkelman2018). Let us consider one of the strongest arguments for this claim.

One popular view amongst philosophers of biology is that species are “historical entities” or, as it is sometimes put, they are individuals (Hull, Reference Hull1978; Ereshefsky, Reference Ereshefsky2000).Footnote 13 Consider the element gold. Something is gold if, and only if, it has atomic number 79. According to many philosophers and biologists, species are not like periodic elements. First, they are temporally bounded in that they have a beginning and an end in time. Second, they are spatially localized having a geographical distribution. Third, the organisms of species interact causally at a time (cohesion) and through time as well (integration) via various intraspecies processes. Gold is not like this since something is gold simply in virtue of having atomic number 79. It can occur in principle anywhere and elements of gold need not have anything to do with one another.

Here then is an argument against the possibility of de-extinction (for a discussion, see Campbell and Whittle, Reference Campbell and Whittle2017; Slater and Clatterbuck, Reference Slater and Clatterbuck2018). A species can evolve only if traits of organisms in the species are heritable. But a trait is heritable in a species only if organisms between generations are causally connected. Any entity whose parts are causally connected is a historical entity. Therefore, species are historical entities. De-extinction requires that organisms of a species exist at two separate times but which are not causally connected between those two times. But this is impossible. Hence, de-extinction is impossible.

To make this more concrete, let us consider the last generation of woolly mammoths on Wrangel Island and some that are created through cloning or genetic engineering (assuming it is successful). One might think that the former does not give birth to the latter since the latter was produced in a laboratory. So, they are not causally connected by heredity and thus the two populations do not share a history. They are not parts of the same historical entity, Mammuthus primigenius. But this argument fails (Campbell and Whittle, Reference Campbell and Whittle2017; Slater and Clatterbuck, Reference Slater and Clatterbuck2018; Campbell, Reference Campbell2022). To see why, consider a human baby who is born through in vitro fertilization. There is a clear sense in which ordinary reproduction has not occurred; it is a form of human-facilitated reproduction. Nevertheless, we do not think that the baby is not a member or part of Homo sapiens. They are nevertheless human. The same should be said regarding de-extinction. There is a causal connection between populations through human-facilitated reproduction as well.Footnote 14

One might object that the woolly mammoth created through cloning or genetic engineering is a “mammophant” and not a genuine mammoth since it has Asian elephant DNA. It is a hybrid or a chimera. But hybridization and horizontal gene transfer occur throughout the natural world (Piotrowska, Reference Piotrowska2018). For example, all the brown bear (Ursus arctos) populations on the Admirality, Baranof and Chichagof islands possess polar bear mitochondria with less than 1% of their nuclear DNA from polar bear ancestry (Cahill et al., Reference Cahill, Green, Fulton, Stiller, Jay, Ovsyanikov and Shapiro2013). They are still brown bears. We know that humans for example interbred with Neanderthals and Denisovans, yet we are still members or parts of H. sapiens (Rogers et al., Reference Rogers, Harris and Achenbach2020). Additionally, mammophants would belong to a relevant woolly mammoth species according to some species concepts (Slater and Clatterbuck, Reference Slater and Clatterbuck2018, pp. 8–11).

Another objection comes from Katz (Reference Katz2022). He claims that with biological systems, there is no design. Humans, and only humans, design objects. However, designing something even in part changes it into an artifact. By recreating and resurrecting species, we are creating artifacts that lack the “integrity” that natural objects possess. Additionally, this sort of design contributes to the domination of the natural world by humans which is morally wrong. There are several problems with this argument (for responses to Katz, see Browning and Veit, Reference Browning and Veit2022; Lean, Reference Lean2022; Preston, Reference Preston2022; Reydon, Reference Reydon2022; Sandler et al., Reference Sandler, Stabell, Baylon, Lundgren, Weisbeek, Yelle and Zaba2022; Turner, Reference Turner2022). First, as many philosophers of biology and biologists argue, there can be design without designers (Kitcher, Reference Kitcher1993). Natural selection is one such designing process.Footnote 15 Second, the argument rests on a flawed dualism between humans and the rest of nature. Humans are an extraordinarily unique and complicated mammal, but we are an evolved species amongst many others. As a species, we have radically changed our planet. Given most of us are moral agents, we can be morally responsible for those changes.Footnote 16 This concerns our status as persons and not as humans. Finally, even if we are dominating the planet and it is morally wrong, it is not clear how much a few instances of de-extinction will contribute to this. Many promote de-extinction as a form of restoration ecology; we are restoring ecological functions to ecosystems.Footnote 17

A different sort of worry is that resurrected species are in some sense “inauthentic” (Siipi, Reference Siipi, Oksanen and Siipi2014). When we say something is inauthentic, we are saying either that it is not identical to the object of interest or it does not share many of the properties that the target of interest possesses (Siipi, Reference Siipi, Oksanen and Siipi2014, pp. 77–78).Footnote 18 For example, there is no analog community for the woolly mammoths since many of the species that it would have existed with no longer exist. But the same can be said of translocation or assisted migration (Novak, Reference Novak2018, p. 5). For example, wolves (Canis lupus) were reintroduced (or relocated) to Yellowstone National Park for the purposes of restoration and the recreation of trophic cascades (Fritts et al., Reference Fritts, Bangs, Fontaine, Johnson, Phillips, Koch and Gunson1997). Though the pack reintroduced did not descend from the last wolves eradicated in Yellowstone around 1926, they are of the same species. Likewise, as climate change alters the environments of many species, we may relocate them to places where their peer species are not present (Schwartz et al., Reference Schwartz, Hellmann, McLachlan, Sax, Borevitz, Brennan and Zellmer2012). This does not mean that they are a different or “inauthentic” species taxa any more than species aided with assistant migration.

In the end, there are a variety of technical issues associated with resurrecting or recreating species using de-extinction technologies. Nevertheless, it does appear possible to recreate or resurrect some lost species.

Is de-extinction morally permissible?

We now consider the most important arguments for and against de-extinction (for surveys, see Sandler, Reference Sandler2014; Rohwer and Marris, Reference Rohwer and Marris2018).

One common argument for de-extinction comes from considerations of restorative justice (Cohen, Reference Cohen2014; Jebari, Reference Jebari2016). When a moral agent harms a moral subject, the former owes the latter restitution. Humans harmed woolly mammoths for example by driving them extinct in combination with others factors like climate change (Martin, Reference Martin2005). Thus, humans owe them restitution or compensation for that harm. The most apt form of restitution would be to resurrect the species. Therefore, we should resurrect woolly mammoths if it possible. As we saw in the last section, though there may be technical impediments to resurrecting the woolly mammoth, it is possible.

One immediate objection to the argument is the individual organisms harmed are long dead and they cannot be resurrected. This is true but beside the point since the harm of extinction befalls a species and not individual organisms.Footnote 19 A different objection to the argument from restoration is that we do not owe extinct species restitution since we did not drive them extinct. We were not alive then. We thus do not owe them anything (Campbell and Whittle, Reference Campbell and Whittle2017).Footnote 20 This argument has force when we consider woolly mammoths, but it might have less force when we consider the passenger pigeon. After all, Americans killed passenger pigeons for their own material benefit. Thus, Americans who benefited from their extinction (even if they did not drive them extinct) might owe them restitution through de-extinction.Footnote 21

Here is another argument for de-extinction from considerations of the conservation of biodiversity (Campbell and Whittle, Reference Campbell and Whittle2017; Iacona et al., Reference Iacona, Maloney, Chadès, Bennett, Seddon and Possingham2017). We should conserve and restore biodiversity. De-extinction is a means to conserve and restore species (and thus biodiversity). Thus, we should resurrect and restore species. Conservationists recognize the importance of preventing species from becoming threatened, endangered and eventually extinct. De-extinction raises the possibility of taking an extinct species and changing it conservation status (Campbell and Whittle, Reference Campbell and Whittle2017, p. 91). Of course, our obligation to conserve and restore biodiversity is a prima facie obligation; it can be outweighed by other morally factors.Footnote 22 For example, if resurrecting a species creates a harmful invasive, then we may have good reason not to do it. As a special case of restoration (or rewilding), consider the restoration of the mammoth steppe (Josh Donlan et al., Reference Josh Donlan, Berger, Bock, Bock, Burney, Estes, Foreman, Martin, Roemer, Smith, Soulé and Greene2006; McCauley et al., Reference McCauley, Hardesty‐Moore, Halpern and Young2017). By resurrecting or recreating the woolly mammoth, we restore ecological functions performed by megaherbivores in the recreation of grasslands that will help prevent climate change. Of course, this assumes that those functions can be performed in a changed environment, and there is not another appropriate species that could do it short of de-extinction.Footnote 23

Let us turn to some of the most important objections to de-extinction.

The first argument against de-extinction concerns animal welfare (Kasperbauer, Reference Kasperbauer2017; Browning, Reference Browning2018; Browning and Veit, Reference Browning and Veit2022). It is morally wrong to cause a sentient being unnecessary suffering. De-extinction will cause unnecessary suffering. Therefore, it is morally wrong to recreate and resurrect species. As a case in point, consider the bucardo cloned and born in 2003. Due to its deformed lungs, it lived for a brief time in tremendous pain (Cohen, Reference Cohen2014). De-extinction could lead to “miscarriage, stillbirth, early death, genetic abnormality and chronic disease” as the result of cloning (Browning, Reference Browning2018, p. 789). And these are just the beginnings of the ethical issues since there are others regarding rearing and reintroducing these animals. However, conservation always involves a balance between protecting and restoring species and the welfare of individual organisms. For example, in places such as New Zealand endemic biodiversity is protected from predatory mammals through multi-kill traps and aerial poisons (Butler et al., Reference Butler, Lindsay and Hunt2014). Our obligations to conserve and restore biodiversity can be outweighed by conservations of animal welfare, but the extent to which there can be “compassionate conservation” is an active debate in conservation practice.

Another argument against de-extinction is the argument from hubris (or “playing God”) (Minteer, Reference Minteer2014, Reference Minteer2019; Diehm, Reference Diehm2017). It is morally wrong to be hubristic (i.e., overly self-confident). De-extinction is hubristic insofar we overestimate our ability to predict and control resurrect or recreated species or ecosystems more generally. As Ben Minteer writes,

Attempting to revive lost species is in many ways a refusal to accept our moral and technological limits in nature. De-extinction thus reflects a new kind of Promethean spirit that attempts to leverage our boundless cleverness and powerful tools for conservation rather than for human enhancement. But things did not end very well for Prometheus. (Minteer, Reference Minteer2014, p. 261)

There are several ways to respond to this argument. First, recreating or resurrecting species can be hubristic, but it is not necessarily so. For example, proponents of de-extinction are very much aware of the limitations of all the various techniques involved. As we discussed, we could only resurrect only a tiny fraction of all the species that have gone extinct. Second, this objection serves as an important moral call to continually avoid overestimating our abilities or underestimating the uncertainties or risks. Third, if sound, this argument would suggest we should avoid all manner of technologies not the least of which is de-extinction. After all, cloning and gene editing alone are only the most dazzling of our current technologies but conservationists also use camera traps, tracking tags, remote sensing, acoustic sensors, drones, eDNA and artificial intelligence. Should we avoid those as well because they may involve hubris?

A final ethical argument against de-extinction is that it is a poor allocation of conservation resources (Bennett et al., Reference Bennett, Maloney, Steeves, Brazill-Boast, Possingham and Seddon2017). Conservation is an underfunded practice. Resources should be allocated to that which will do the most good in conserving and restoring biodiversity. However, de-extinction will do little for that aim. Thus, funds should not be allocated to it. There are several objections that might be raised to this argument. First, there is a crucial assumption here: If money (or other resources) had not gone to a de-extinction project, then they would have gone to conservation work. But this may not be true since some de-extinction projects will be funded by those would not otherwise give to conservation. Efforts to bring back the heath hen in Martha’s Vineyard appears to be such a case (Sandler, Reference Sandler2017, p. 2). Second, there is an assumption that ordinary conservation and de-extinction are mutually exclusive and that need not be the case. For example, there are good reasons to take tissue samples with DNA for “frozen zoos” or seed banks independent of whether they are used for de-extinction (Ryder et al., Reference Ryder, McLaren, Brenner, Zhang and Benirschke2000). After all, if a species disappears “in the wild,” conserving tissue samples may allow us to prevent them from going extinct.

We can now take stock of the moral arguments for and against de-extinction. The general conclusion we have found is that it is morally permissible to resurrect or recreate species except when there are outweighing morally relevant considerations. These moral considerations concern animal welfare, hubris and poor allocation of resources will sometimes outweigh obligations to recreate or resurrect species but not always. Thus, moral decisions regarding de-extinction will often need to be decided on a case-by-case basis.

Conclusion

De-extinction is sometimes thought to be impossible given the nature of species and heredity. It may very well be unlikely, but it is does not appear impossible. Sometimes de-extinction is portrayed as Jurassic Park comes to life with all the morally failings in tow. But it is more accurately portrayed as a complicated moral issue without simple, easy answers.

Open peer review

To view the open peer review materials for this article, please visit http://doi.org/10.1017/ext.2023.4.

Acknowledgements

My thanks to Hank Greeley for putting together a conference in May 2013 entitled “De-extinction: Ethics, Law & Politics” at Stanford University. There were many different participants including Stewart Brand and Beth Shapiro. There were also other philosophers including Hilary Bok and Ronald Sandler. I learned a great deal from the experience, and it forms the background of this essay. Additionally, I thank the two anonymous reviewers for their very helpful comments.

Footnotes

1. https://www.croptrust.org/work/svalbard-global-seed-vault/.

2. Christopher H. Lean argues that “De-extinction is better thought of as a set of techniques utilizing the remnants of extinct populations” (Reference Lean2020, p. 4). We need not recreate or resurrect species so much as use extinct populations as resources for introducing variation into taxa of interest. It is also worth noting that de-extinction techniques can be applied to several different units including genes, species, and ecosystems (Campbell and Whittle, Reference Campbell and Whittle2017, pp. 8–11).

3. For another discussion of inclusive definitions of “de-extinction,” see Campbell (Reference Campbell2016).

4. There are limitations to back-breeding for the purposes of de-extinction. First, the ancestral trait must be found in an extant species which is closely related to the target extinct species. Second, the phenotypic matching needs to be the result of the same genes (or gene–environment interaction). Third, back-breeding can also create inbreeding depression lowering the fitness of individuals of the extant species, which may defeat the purpose of de-extinction.

5. In 2015, the auroch genome was fully sequenced from DNA extracted from a 6,750-year-old British auroch bone (Park et al., Reference Park, Magee, McGettigan, Teasdale, Edwards, Lohan and MacHugh2015). This opens the door to using some of the other de-extinction techniques we will discuss.

6. There are difficulties with this technique too. First, a small percentage of potential clones develop into living organisms. Second, cloning requires intact living cells from the extinct species which are often not available. Sometimes cloning can still occur when cells are not well-preserved. For example, an endangered subspecies of sheep, the mouflon (Ovis gmelini), was cloned from a nonviable cell of a dead sheep found in a field (Loi et al., Reference Loi, Ptak, Barboni, Fulka, Cappai and Clinton2001). However, for very recent extinct species, cells can be collected and preserved.

7. George Church has proposed resurrecting or recreating woolly mammoths through genetic engineering (https://www.techtimes.com/articles/226529/20180430/scientists-might-create-mammoth-elephant-hybrid-after-resurrecting-44-genes-will-start-with-mice-first.htm). The woolly mammoth’s and the Asian elephant’s genomes have been sequenced. Of the genetic differences between them, only 2,020 mutations affect genes that code for proteins. These genes affect phenotypic traits like hairiness, ear length, cold tolerance, and so forth. Using CRISPR gene editing technologies, Church and colleagues can excise the Asian elephant genes and replace them with woolly mammoth ones. Thus, they are in the first stages of creating what some call a “mammophant” – a cold-tolerant Asian elephant.

8. For example, a genome was reconstructed from a 700,000-year-old bone from a horse (Shapiro, Reference Shapiro2017, p. 4).

9. There are limitations with this technique since DNA degrades more quickly in hot, wet environments than in cold, dry ones. Likewise, it is more difficult to reconstruct genomes when there are no close living relatives as with the New Zealand moa (Dinornithiformes).

10. https://www.si.edu/spotlight/passenger-pigeon.

11. Revive & Restore (https://reviverestore.org/about-us/) is an important organization dedicated to using biotechnology for conservation that was founded by Stuart Brand and Ryan Phelan. Several of their projects include recreating or resurrecting extinct species such as the passenger pigeon.

12. Philosophers have noted that there are different kinds of impossibility (and thus possibility). First, something is conceptually impossible it is logically inconsistent. Second, something is physically impossible when it is inconsistent with the laws of nature. Third, something is technologically impossible when it cannot occur given the current state of technology. The debates over de-extinction largely concern the first two notions of impossibility.

13. According to some philosophers, an individual is an entity that has a beginning and an end whose parts are integrated synchronically and diachronically (Mishler and Brandon, Reference Mishler and Brandon1987). It is clear that a species’ parts (i.e., organisms) may be only weakly integrated through processes like interbreeding even if they have a beginning via speciation and an end via extinction. Many philosophers as a result prefer the term “historical entity” to “individual.”

14. It is worth emphasizing that even if resurrecting an extinct is possible, not every successful case of de-extinction is a resurrection. Back-breeding does not resurrect species so much as recreate them in our terminology. The argument here is some cases of de-extinction may be resurrections.

15. Interestingly, cultural evolution appears to be another such process (Boyd and Richerson, Reference Boyd and Richerson1988; Richerson and Boyd, Reference Richerson and Boyd2008). However, contrary to Katz (Reference Katz1997), human culture may design objects without intention.

16. A moral agent is a person who one who can make free decisions, can understand the consequences of their choices, and thus is morally responsible for their decisions. A moral subject is one who has a well-being; that is, can be benefited or harmed. Every moral agent is a moral subject but not necessarily vice versa.

17. To be fair, Katz (Reference Katz1997) opposes restoration ecology as well for similar reasons.

18. A different sort of worry is whether authenticity is even a scientific notion at all. For an attempt to show how it is a scientific notion, see Dudley (Reference Dudley2012).

19. This raises ethical issues about whether species themselves can be harmed given that they are not sentient though their members or parts are (Campbell and Whittle, Reference Campbell and Whittle2017; Kasperbauer, Reference Kasperbauer2017). Due to space, we cannot address those issues here (though see Sandler, Reference Sandler2012).

20. This response turns on whether the wrongdoing was done by a group of humans or by our species.

21. For further discussion of this type of argument, see Cottrell et al. (Reference Cottrell, Jensen and Peck2014) and Lean (Reference Lean2020).

22. An action is a prima facie obligation when it possesses a morally relevant feature and if that were the only morally relevant feature, then one would be obliged to do it.

23. One might object that the restoration of ecological function does not require us to resurrect or recreate a species. For example, a mammophant would be sufficient to restore the mammoth steppe. But this just is a form of de-extinction and so is not an objection to the above argument.

References

Akbar, PG, Nugroho, TW, Suranto, M and Fauzan, MR (2020) Missing for 170 years—The rediscovery of Black-browed Babbler Malacocincla perspicillata on Borneo. BirdingASIA 34, 13–14.Google Scholar
Allaby, M (1992) The Concise Oxford Dictionary of Botany. Oxford: Oxford University Press.Google Scholar
Allentoft, ME, Collins, M, Harker, D, Haile, J, Oskam, CL, Hale, ML, … Bunce, M (2012) The half-life of DNA in bone: Measuring decay kinetics in 158 dated fossils. Proceedings of the Royal Society B: Biological Sciences 279(1748), 4724–4733.CrossRefGoogle ScholarPubMed
Bennett, JR, Maloney, RF, Steeves, TE, Brazill-Boast, J, Possingham, HP and Seddon, PJ (2017) Spending limited resources on de-extinction could lead to net biodiversity loss. Nature Ecology & Evolution 1(4), 1–4.CrossRefGoogle ScholarPubMed
Boyd, R and Richerson, PJ (1988) Culture and the Evolutionary Process. Chicago, IL: University of Chicago Press.Google Scholar
Browning, H (2018) Won’t somebody please think of the mammoths? De-extinction and animal welfare. Journal of Agricultural and Environmental Ethics 31(6), 785–803.CrossRefGoogle Scholar
Browning, H and Veit, W (2022) More than zombies: Considering the animal subject in de-extinction. Ethics, Policy & Environment 25, 121–124.CrossRefGoogle Scholar
Butler, D, Lindsay, T and Hunt, J (2014) Paradise Saved: The Remarkable Story of New Zealand’s Wildlife Sanctuaries and How They Are Stemming the Tide of Extinction. Auckland, New Zealand: Random House New Zealand.Google Scholar
Cahill, JA, Green, RE, Fulton, TL, Stiller, M, Jay, F, Ovsyanikov, N, … Shapiro, B (2013) Genomic evidence for island population conversion resolves conflicting theories of polar bear evolution. PLoS Genetics 9(3), e1003345.CrossRefGoogle ScholarPubMed
Campbell, D (2016) A case for resurrecting lost species—Review essay of Beth Shapiro’s, “how to clone a mammoth: The science of De-extinction”. Biology and Philosophy 31(5), 747–759.CrossRefGoogle Scholar
Campbell, DI (2022) Why Katz is wrong: A lab-created creature can still have an ancient evolutionary history. Ethics, Policy & Environment 25, 109–112.CrossRefGoogle Scholar
Campbell, DI and Whittle, PM (2017) Resurrecting Extinct Species: Ethics and Authenticity. Palgrave Macmillan Cham.CrossRefGoogle Scholar
Cohen, S (2014) The ethics of de-extinction. NanoEthics 8(2), 165–178.CrossRefGoogle Scholar
Cottrell, S, Jensen, JL and Peck, SL (2014) Resuscitation and resurrection: The ethics of cloning cheetahs, mammoths, and Neanderthals. Life Sciences, Society and Policy 10(1), 1–17.CrossRefGoogle Scholar
Diehm, C (2017) De-extinction and deep questions about species conservation. Ethics, Policy & Environment 20(1), 25–28.CrossRefGoogle Scholar
Dudley, N (2012). Authenticity innature: making choices about the naturalness of ecosystems. Routledge. ChicagoCrossRefGoogle Scholar
Ereshefsky, M (2000) The Poverty of the Linnaean Hierarchy: A Philosophical Study of Biological Taxonomy. Cambridge: Cambridge University Press.CrossRefGoogle Scholar
Finkelman, L (2018) De-extinction and the conception of species. Biology and Philosophy 33(5), 1–18.CrossRefGoogle Scholar
Fritts, SH, Bangs, EE, Fontaine, JA, Johnson, MR, Phillips, MK, Koch, ED and Gunson, JR (1997) Planning and implementing a reintroduction of wolves to Yellowstone National Park and Central Idaho. Restoration Ecology 5(1), 7–27.CrossRefGoogle Scholar
Gunn, AS (1991) The restoration of species and natural environments. Environmental Ethics 13(4), 291–310.CrossRefGoogle Scholar
Hannah, M (2021) Extinctions: Living and Dying in the Margin of Error. Cambridge: Cambridge University Press.CrossRefGoogle Scholar
Hull, DL (1978) A matter of individuality. Philosophy of Science 45(3), 335–360.CrossRefGoogle Scholar
Iacona, G, Maloney, RF, Chadès, I, Bennett, JR, Seddon, PJ and Possingham, HP (2017) Prioritizing revived species: What are the conservation management implications of de-extinction? Functional Ecology 31(5), 1041–1048.CrossRefGoogle Scholar
Jebari, K (2016) Should extinction be forever? Philosophy & Technology 29(3), 211–222.CrossRefGoogle Scholar
Josh Donlan, C, Berger, J, Bock, CE, Bock, JH, Burney, DA, Estes, JA, Foreman, D, Martin, PS, Roemer, GW, Smith, FA, Soulé, ME and Greene, HW (2006) Pleistocene rewilding: An optimistic agenda for twenty-first century conservation. The American Naturalist 168(5), 660–681.CrossRefGoogle ScholarPubMed
Kasperbauer, TJ (2017) Should we bring back the passenger pigeon? The ethics of de-extinction. Ethics, Policy & Environment 20(1), 1–14.CrossRefGoogle Scholar
Katz, E (1997) Nature as Subject: Human Obligation and Natural Community. Lanham, MD: Rowman & Littlefield.Google Scholar
Katz, E (2022) Considering de-extinction: Zombie arguments and the walking (and flying and swimming) dead. Ethics, Policy & Environment 25, 81–103.CrossRefGoogle Scholar
Kitcher, P (1993) Function and design. Midwest Studies in Philosophy 18, 379–397.CrossRefGoogle Scholar
Lean, CH (2020) Why wake the dead? Identity and de-extinction. Journal of Agricultural and Environmental Ethics 33(3), 571–589.CrossRefGoogle Scholar
Lean, CH (2022) Authenticity and autonomy in de-extinction. Ethics, Policy & Environment 25, 116–120.CrossRefGoogle Scholar
Leopold, A (1949) A Sand County Almanac: And Sketches Here and There. Oxford: Oxford University Press.Google Scholar
Loi, P, Ptak, G, Barboni, B, Fulka, J, Cappai, P and Clinton, M (2001) Genetic rescue of an endangered mammal by cross-species nuclear transfer using post-mortem somatic cells. Nature Biotechnology 19(10), 962–964.CrossRefGoogle ScholarPubMed
Martin, PS (2005) Twilight of the Mammoths: Ice Age Extinctions and the Rewilding of America, Vol. 8. Berkeley, CA: University of California Press.Google Scholar
McCauley, DJ, Hardesty‐Moore, M, Halpern, BS and Young, HS (2017) A mammoth undertaking: Harnessing insight from functional ecology to shape de‐extinction priority setting. Functional Ecology 31(5), 1003–1011.CrossRefGoogle Scholar
Minteer, B (2014) Is it right to reverse extinction? Nature 509(7500), 261.CrossRefGoogle ScholarPubMed
Minteer, B (2019) The Fall of the Wild: Extinction, De-Extinction, and the Ethics of Conservation. New York: Columbia University Press.Google Scholar
Mishler, BD and Brandon, RN (1987). Individuality, pluralism, and the phylogenetic species concept. Biology and Philosophy, 2, 397–414.CrossRefGoogle Scholar
Novak, BJ (2018) De-extinction. Genes 9(11), 548.CrossRefGoogle ScholarPubMed
Park, SD, Magee, DA, McGettigan, PA, Teasdale, MD, Edwards, CJ, Lohan, AJ, … MacHugh, DE (2015) Genome sequencing of the extinct Eurasian wild aurochs, Bos primigenius, illuminates the phylogeography and evolution of cattle. Genome Biology 16(1), 1–15.CrossRefGoogle ScholarPubMed
Piotrowska, M (2018) Meet the new mammoth, same as the old? Resurrecting the Mammuthus primigenius. Biology and Philosophy 33(1), 1–16.CrossRefGoogle Scholar
Preston, C (2022) How worried should I be about zombies? Ethics, Policy & Environment 25, 129–131.CrossRefGoogle Scholar
Reydon, TA (2022) Deflating the de-extinction debates: Domination and Artifactuality are not the problem. Ethics, Policy & Environment 25(2), 113–115.CrossRefGoogle Scholar
Richerson, PJ and Boyd, R (2008) Not by Genes Alone: How Culture Transformed Human Evolution. Chicago, IL: University of Chicago Press.Google Scholar
Rogers, AR, Harris, NS and Achenbach, AA (2020) Neanderthal-Denisovan ancestors interbred with a distantly related hominin. Science Advances 6(8), eaay5483.CrossRefGoogle ScholarPubMed
Rohwer, Y and Marris, E (2018) An analysis of potential ethical justifications for mammoth de-extinction and a call for empirical research. Ethics, Policy & Environment 21(1), 127–142.CrossRefGoogle Scholar
Ryder, OA, McLaren, A, Brenner, S, Zhang, Y-P and Benirschke, K (2000) DNA banks for endangered animal species. Science 288(5464), 275–277.CrossRefGoogle ScholarPubMed
Sandler, RL (2012) The Ethics of Species: An Introduction. Cambridge: Cambridge University Press.CrossRefGoogle Scholar
Sandler, RL (2014) The ethics of reviving long extinct species. Conservation Biology 28(2), 354–360.CrossRefGoogle ScholarPubMed
Sandler, RL (2017) De-extinction: Costs, benefits and ethics. Nature Ecology & Evolution 1(4), 1–2.CrossRefGoogle ScholarPubMed
Sandler, R, Stabell, ED, Baylon, R, Lundgren, C, Weisbeek, P, Yelle, B and Zaba, M (2022) Eric Katz on “de-extinction”: Ontology, value and normativity. Ethics, Policy & Environment 25, 104–108.CrossRefGoogle Scholar
Schwartz, MW, Hellmann, JJ, McLachlan, JM, Sax, DF, Borevitz, JO, Brennan, J, … Zellmer, S (2012) Managed relocation: Integrating the scientific, regulatory, and ethical challenges. Bioscience 62(8), 732–743.CrossRefGoogle Scholar
Shapiro, B (2015) How to Clone a Mammoth: The Science of De-Extinction. Princeton, NJ: Princeton University Press.Google Scholar
Shapiro, B (2017) Pathways to de‐extinction: How close can we get to resurrection of an extinct species? Functional Ecology 31(5), 996–1002.CrossRefGoogle Scholar
Sherkow, JS and Greely, HT (2013) What if extinction is not forever? Science 340(6128), 32–33.CrossRefGoogle Scholar
Siipi, H (2014) The authenticity of animals. In Oksanen, M and Siipi, H (eds), The Ethics of Animal re-Creation and Modification: Reviving, Rewilding, Restoring. London: Palgrave Macmillan, pp. 77–98.CrossRefGoogle Scholar
Siipi, H and Finkelman, L (2017) The extinction and de-extinction of species. Philosophy & Technology 30(4), 427–441.CrossRefGoogle Scholar
Slater, MH and Clatterbuck, H (2018) A pragmatic approach to the possibility of de-extinction. Biology and Philosophy 33(1), 1–21.CrossRefGoogle Scholar
Stuart, AJ, Kosintsev, PA, Higham, TF and Lister, AM (2004) Pleistocene to Holocene extinction dynamics in giant deer and woolly mammoth. Nature 431(7009), 684–689.CrossRefGoogle ScholarPubMed
Turner, D (2022) Causal history, environmental art, and biotechnologically assisted restoration. Ethics, Policy & Environment 25, 125–128.CrossRefGoogle Scholar
Vartanyan, SL, Arslanov, KA, Tertychnaya, TV and Chernov, S (1995) Radiocarbon dating evidence for mammoths on Wrangel island, arctic ocean, until 2000 BC. Radiocarbon 37(1), 1–6.CrossRefGoogle Scholar
Yashina, S, Gubin, S, Maksimovich, S, Yashina, A, Gakhova, E and Gilichinsky, D (2012). Regeneration of whole fertile plants from 30,000-y-old fruit tissue buried in Siberian permafrost. Proceedings of the National Academy of Sciences, 109(10), 4008–4013.CrossRefGoogle ScholarPubMed
Zimov, SA (2005) Pleistocene park: Return of the mammoth’s ecosystem. Science 308(5723), 796–798.CrossRefGoogle ScholarPubMed

Author comment: Philosophy and ethics of de-extinction — R0/PR1

Published online by Cambridge University Press:  30 January 2023
DOI: https://doi.org/10.1017/ext.2023.4.pr1 [Opens in a new window]
Jay Odenbaugh [Opens in a new window] Philosophy, Lewis & Clark College, United States
Revision round: 0
Role: author

Comments

This is an invited essay surveying philosophical and ethical issues regarding de-extinction. The first part of the essay clarifies both what extinction is but also de-extinction. I then turn to considering arguments that conclude de-extinction is not possible and then to arguments concerning the ethics of de-extinction. If there are any questions, feel free to be in touch with me.

Review: Philosophy and ethics of de-extinction — R0/PR2

Published online by Cambridge University Press:  30 January 2023
DOI: https://doi.org/10.1017/ext.2023.4.pr2 [Opens in a new window]
Matthew Slater [Opens in a new window] Philosophy, Bucknell University, United States
Revision round: 0
Role: reviewer
Recommendation/decision: accept

Conflict of interest statement

Reviewer declares none.

Comments

Comments to Author: This strikes me as a badly needed and (below issues notwithstanding) exceedingly clear review essay on the myriad debates about de-extinction. I would (generously) describe such debates as often exhibiting more heat than light, so it’s a boon to have a systematic, careful discussion of them. The author efficiently walks through many of the main critical arguments concerning the possibility and acceptability of de-extinction, deftly weaving together insights from biology, philosophy of biology, ethics, and environmental philosophy. I would, however, offer a few suggestions for them to consider in revising the paper. I direct the commentary now to the author.

As a minor terminological point, I don’t love the metaphor of ‘resurrection’. To my mind, it encourages a misleading view of what de-extinction requires. To resurrect a person (or non-human animal), whether by miraculous or technological, means bringing back the self-same being. Nothing like this is obviously required for de-extinction. Instead, and I think you agree with this interpretation, the idea is that we’re bringing back the same *kind* of organisms (or extending a lineage). I realize that conveying the former interpretation is not your intent and agree with you (and Shapiro) in finding ‘de-extincted’ to be an unappealing verb (perhaps ‘DE-ed’ for short is passable?), but I wanted to flag it. If you stick with ‘resurrection’, I would consider promoting the explanatory footnote to the main text and bear in mind throughout the potential for that metaphor to mislead (particularly on p. 4 in your discussion of Novak).

Concerning your discussion of Michael Hannah’s (2021) definition of extinction (as occurring “when the last individual belonging to that species dies”), I think a bit more clarity is needed on the question of whether this definition “trivializes the notion of extinction”. My take is that what is trivialized is the *impossibility* of de-extinction. This mirrors an argument of Delord (2014) that Clatterbuck and I discussed in our (2018, p. 3): if we did “bring back” members of a (thought-to-be-)extinct species, all we find is that this species wasn’t really extinct after all; for (to use Hannah’s definition) the last member of the species wasn’t dead. While this does trivialize the conceptual case against de-extinction, it doesn’t obviously trivialize the notion of *extinction*, which can remain a substantive question, though it *does* is arguably make our knowing whether an extinction has actually occurred — even when every individual of that species has died — effectively impossible, so long as we cannot rule out that further members won’t be produced at some time in the future. Knowing whether a species is extinct becomes (in part) a matter of prediction.

It seems to me that there is an ambiguity in our use of ‘last’ that applies to Hannah’s definition in a way that defangs the conceptual argument against de-extinction. Sometimes ‘last’ means “last in a given (potentially vaguely defined) time period”; other times it is not so restricted. For example, a relieved university dean says “Okay, that’s the last student to receive their diploma; commencement is now over.” It would be foolish to reply “No, it’s actually *not* over, as there are more students who will receive their diplomas in the future [e.g., next year]!” This sort of response is clearly to be distinguished from one in which the dean takes commencement to be over only to be alerted that they missed a name: what they *thought* was the last student due to receive a diploma wasn’t in fact the last (for the relevant time period).

Moving on: on p. 4, responding to Novak, you write that “[his] definitions of de-extinction are inclusive.” I’d explain in more detail what you mean by this.

p. 5: “Notice that back-breeding *recreates the auroch* by virtue of reestablishing auroch-like traits though the auroch is not resurrected.” Does it? I feel like the starred bit deserves a hedge or further argument (even setting aside the question of whether “recreating” a species constitutes a de-extinction).

p. 6: “Woolly mammoths are more closely related to Asian elephants (Elephas maximus) than African ones (Loxodonta). Thus, in principle they could be cloned with Asian elephant mothers.” I wouldn’t think the second sentence follows from the first. There may be independent reasons for thinking that the second sentence is true, of course (and the closer phylogenetic proximity might make it *more likely* that this is possible).

Considering the worry about Asian elephants being endangered (p. 6), it might be worth pointing out that there would presumably be other de-extinction candidates for which this is *not* the case. Reorganizing this discussion to start with the general point about closely-related surrogates and then raising the concern that some of these surrogates may entail their own ethical challenges could improve the flow of ideas here.

Also: It is an open-and-shut case that a “mammophant” wouldn’t be a genuine mammoth (supposing that it is a genetic clone of a mammoth)? Admittedly, there’s *some* reason for thinking not (the surrogacy issue, mitochondrial DNA, epigenetic effects, and so on), but if we ask the question to what species does this creature belong, on at least some species concepts, it seems plausible that the right answer is to the relevant mammoth species (see discussion in Slater & Clatterbuck 2018, pp. 8–11).

You begin section 2: “Philosophers have argued about whether de-extinction is even possible. This issue is not whether it is difficult or even unlikely that a species will be resurrected or recreated.” I would suggest clarifying the types of possibility you have in mind here — maybe ‘conceptually possible’ for the philosophical question and whether it is ‘technologically [or scientifically / practically] difficult / feasible’?

I’m not sure I’m grasping the authenticity argument (pp. 14–15); is it supposed to be relevant to the scientific or conceptual question of the possibility of de-extinction? If so, hard for me to see how it works; one obvious reply would be to point out that “authenticity” is not a precise concept of any biological science (that I’m aware of, anyway). This is compatible of course with your arguments, as I read them. Perhaps a very charitable reconstruction of the argument would be useful here.

When discussing criticisms of the moral case for particular de-extinction projects stemming from it not being *we* who “owe extinct species restitution since we did not drive them extinct” (since we weren’t alive in the Pleistocene!), you write that “This argument has force when we consider woolly mammoths, but it might have less force when we consider the passenger pigeon. After all, Americans killed passenger pigeons for their own material benefit.” Why not think it is simply equally bad, since, again, *we* were not the people who shot all the passenger pigeons (even if we’re compatriots with the culprits)! More could be said here I think. Is it that we — as Americans? as people living more proximately to the actual culprits? — somehow enjoy more advantaged from the extermination of passenger pigeons and so owe a debt of some sort? It’s not clear to me that a similar (more widely-applicable) advantage might not have stemmed from our Pleistocene forebears hunting mammoths. . . .

p. 19: in the discussion of the argument from hubris, I wonder if the response doesn’t strawman things a bit. Sure, the proponents are aware of the technical challenges and limitations and such, but I didn’t take the argument to be objecting to some kind of technical overconfidence, but to the very idea of intervening in this way at all — something that might eventually make us cavalier about letting species go extinct (or driving them there) in the first place. If that’s right, then the summary reply (“It would take a much stronger argument to show that by our nature we cannot avoid hubris”) would seem to miss the mark; the question is not whether this is something about “our nature” but whether it is an attitude that (whatever its source) should be resisted.

This strikes me as a badly needed and (below issues notwithstanding) quite clear review essay on the debates about de-extinction. I would (generously) describe these debates as exhibited more heat than light, so it’s a boon to have a systematic discussion of them. The author efficiently walks through many of the main critical arguments concerning the possibility and acceptability of de-extinction, deftly weaving together insights from biology, philosophy of biology, ethics, and environmental philosophy. I recommend acceptance, though I did have several suggestions that I’d encourage the author to consider while revising.

p. 2: I don’t love the metaphor of ‘resurrection’ since (to my mind) it seems carry a very particular (robust? weighty?) understanding of what de-extinction would require. I realize that this is not your intent (as is made clear in FN1), and I don’t have much better to suggest (other than ‘DE-ed’ perhaps), but I just wanted to flag it.

p. 3: It might be worth trying to be a little clearer on the discussion of whether ‘extinction’ is trivialized somehow by the response sketched. I know that there are arguments against de-extinction that trivialize *that* notion — e.g., DeLord argues (if I remember correctly) that if a member of a species is “brought back” then it was not truly extinct. Sounds like this discussion is in the neighborhood.

p. 4: “These definitions of de-extinction are inclusive.” Explain meaning of ‘inclusive’.

I might highlight the distinction between the technical senses of ‘resurrected’ and ‘recreated’ as you laid them out earlier (and what they amount to here) in the main text, since this is a key issue. On a fairly natural construal of ‘recreated’ (though *perhaps* not yours), recreating a species could entail resurrecting it.

“To see why, let us consider these three techniques….” (and following): This paragraph read awkwardly to me.

p. 5: “Notice that back-breeding **recreates the auroch** by virtue of reestablishing auroch-like traits though the auroch is not resurrected.” Does it? I feel like the starred bit needs a hedge.

p. 6: “Woolly mammoths are more closely related to Asian elephants (Elephas maximus) than African ones (Loxodonta). Thus, in principle they could be cloned with Asian elephant mothers.” I wouldn’t think the second sentence follows from the first. . . .

Considering the worry about Asian elephants being endangered, it might be worth pointing out that there would presumably be other candidates for which this is *not* the case. I might consider reorganizing this discussion to start with the general point about closely-related surrogates and then raise the concern that some of these surrogates may involve their own ethical challenges.

p. 7: “However, these animals unlike woolly mammoths, cannot knock down trees to create grassland.” Awkward. Rephrase as: “Unlike woolly mammoths, however, these animals cannot knock down trees to create grassland.

In the footnote (“Thus, there are…”) --> ‘…they are’.

Also: It is an open-and-shut case that a “mammophant” wouldn’t be a genuine mammoth (supposing that it is a genetic clone of a mammoth)? Admittedly, there’s *some* reason for thinking not (the surrogacy issue, mitochondrial DNA, epigenetic effects, and so on), but if we ask the question to what species does this creature belong, on at least some species concepts, it seems plausible that the right answer is to the relevant mammoth species.

p. 10: the Shapiro quote is a little strange. Why think that there’s a single goal? That seems like it fits in well to your discussion here and could be brought out a bit more clearly. Again, what we’re talking about under the heading of ‘resurrection’ obviously matters a great deal.

“Philosophers have argued about whether de-extinction is even possible. This issue is not whether it is difficult or even unlikely that a species will be resurrected or recreated.” Clarify the types of possibility here — maybe ‘conceptually possible’ for the philosophical question and whether it is ‘technologically [or scientifically / practically] difficult’?

p. 15: the authenticity argument seems to me very odd. One obvious reply to my mind is to point out that authenticity is not a precise concept of any biological science (that I’m aware of, anyway). This is compatible of course with your arguments; thought it might be worth mentioning.

p. 16: “This argument has force when we consider woolly mammoths, but it might have less force when we consider the passenger pigeon. After all, Americans killed passenger pigeons for their own material benefit.” Less force, yes, but why not think it is equally bad, since again *we* (even if we’re both Americans) were not the people who shot all the passenger pigeons! More could be said here I think. Is it that we (as Americans? as people living more proximately to the actual culprits?) somehow enjoy more advantaged from the extermination of passenger pigeons and so owe a debt? It’s not clear to me that a similar (more widely-applicable) advantage might not have stemmed from our Pleistocene forebears hunting mammoths. . . .

p. 19: in the discussion of the argument from hubris, I wonder if the response doesn’t strawman things; sure, the proponents are aware of the technical challenges and limitations and such, but I didn’t take the argument to be objecting to some kind of technical overconfidence, but to the very idea of intervening in this way at all — something that might eventually make us cavalier about letting species go extinct (or driving them there) in the first place. If that’s right, then the summary reply (“It would take a much stronger argument to show that by our nature we cannot avoid hubris”) would seem to miss the mark; the question is not whether this is something about “our nature” but whether it is an attitude that (whatever its source) should be resisted.

“After all, cloning and gene editing **along** are…” --> ‘alone’ I assume.

p. 20: “there are good reasons to take tissue samples with DNA for “frozen zoos” or seed banks independent of whether they are used for de-extinction….” Briefly explain / mention what these good reasons are?

I found the paragraph right before the conclusion to read a bit awkwardly. Ditto for the conclusion (seemed to be rapidly composed, with some grammatical issues). Why not take a more substantive, thematic stock of the territory covered?

Review: Philosophy and ethics of de-extinction — R0/PR3

Published online by Cambridge University Press:  30 January 2023
DOI: https://doi.org/10.1017/ext.2023.4.pr3 [Opens in a new window]
Revision round: 0
Role: reviewer
Recommendation/decision: accept

Comments

Comments to Author: This looks good to go. I have some minor citations and comments that could be incorporated but this looks like a good summary of this literature.

Page 4. On inclusive definitions. Campbell has an interesting variation on an inclusive definition where it is where it is the expression of adaptive traits “for de-extinction

purposes, Pb counts as being the same species as Pa just to the degree that many of

the evolutionarily adaptive traits possessed by the members of Pa have been genetically inherited by and are phenotypically expressed by members of Pb”

Page 12. The argument at the end of the page may have some similarities with: Piotrowska, M. (2018). Meet the new mammoth, same as the old? Resurrecting the Mammuthus primigenius. Biology & Philosophy, 33(1), 1-16.

Page 15. I think that the following paper deserves a citation for their engagement with the duties argument also: Cottrell, S., Jensen, J. L., & Peck, S. L. (2014). Resuscitation and resurrection: The ethics of cloning cheetahs, mammoths, and Neanderthals. Life Sciences, Society and Policy, 10(1), 3

Page 16. Lean 2020 replies to the duty’s argument at length.

Recommendation: Philosophy and ethics of de-extinction — R0/PR4

Published online by Cambridge University Press:  30 January 2023
DOI: https://doi.org/10.1017/ext.2023.4.pr4 [Opens in a new window]
Kate Lyons School of Biological Sciences, University of Nebraska-Lincoln, United States
Date of review:  19 December 2022
Revision round: 0
Role: Handling Editor
Recommendation/decision: minor-revision

Comments

Comments to Author: Dear Dr. Odenbaugh,

I now have two very positive reviews of your manuscript. While both reviewers recommend acceptance of your paper, they do both have suggestions for improving the manuscript. Therefore, I am recommending minor revision to give you time to incorporate the suggestions you find useful. However, I do not anticipate sending it out for review again. I look forward to seeing a revised manuscript along with a detailed cover letter responding to the reviewer comments.

Sincerely,

Kate Lyons

Senior Editor

Decision: Philosophy and ethics of de-extinction — R0/PR5

Published online by Cambridge University Press:  30 January 2023
DOI: https://doi.org/10.1017/ext.2023.4.pr5 [Opens in a new window]
Barry Brook [Opens in a new window] School of Natural Sciences, University of Tasmania, Australia
Revision round: 0
Role: Editor in Chief
Recommendation/decision: minor-revision

Comments

No accompanying comment.

Author comment: Philosophy and ethics of de-extinction — R1/PR6

Published online by Cambridge University Press:  30 January 2023
DOI: https://doi.org/10.1017/ext.2023.4.pr6 [Opens in a new window]
Jay Odenbaugh [Opens in a new window] Philosophy, Lewis & Clark College, United States
Revision round: 1
Role: author

Comments

Overall, I have found both Reviewer’s comments helpful. Here I address each comment from Reviewer 1 and then Reviewer 2.

1. I agree that ‘resurrection’ is not an ideal term; however, it is already established in the literature. Though it can have a “miraculous” interpretation, in this context it does not. I have retained the term “resurrection” but moved the footnote to the main text as the reviewer requested. On p. 2, I include this sentence, “Resurrection is sometimes associated with bringing back the very organism who has died, and this is not what is being discussed in debates regarding de-extinction. We are discussed higher levels of organization such as populations, species, and the like.”

2. The reviewer worries that Hannah’s notion of extinction does not only trivialize extinction but the impossibility of de-extinction by implication. I have changed the text on p. 3 as follows, “One might object that this response trivializes the notion of extinction (and thus the impossibility of de-extinction).”

3. On Novak’s “inclusive” definition of de-extinction, I have explained my reasons for this terminology by amending the text on p. 3 as follows, “These definitions of de-extinction are inclusive. The reason they are inclusive is that the techniques associated with de-extinction do not require that a species be resurrected but also may be recreated.”

4. The reviewer wonders why recreating auroch-like traits would be recreating the auroch. I address this worry by amending the text on p. 4 this way, “Notice that back-breeding recreates the auroch by virtue of reestablishing auroch-like traits though the auroch is not resurrected. This is because in recreation we create organisms very similar to those of an extinct species even when they are not members of the same species.”

5. Reviewer 1 notes that just because woolly mammoths are more closely related to Asian elephants than African elephants does not imply they could be cloned with Asian elephants. That is true, and I have changed the text to reflect this (p. 5); “Woolly mammoths are more closely related to Asian elephants (Elephas maximus) than African ones (Loxodonta). In principle, they could be cloned with Asian elephant mothers.

6. The reviewer notes that though it is true that Asian elephants are endangered and this raises ethical issues using them as surrogates; this is not true of other surrogate species. I have adjusted the text as follows (p. 5), “One serious ethical problem here is that the Asian elephant is endangered, and egg harvesting, implantation along with pregnancy would likely harm them. Of course, some surrogate species are not endangered.” I have noted that mammophants would belong to relevant woolly mammoth species on some species concepts and added a citation. The text (p. 10) now reads, “Additionally, mammophants would belong to a relevant woolly mammoth species according to some species concepts (Slater & Clatterbuck 2018, 8–11).”

7. Reviewer 1 requested clarifications on the notions of impossibility and possibility at work in these discussions. I have added a footnote on p. 8 which discusses these different notions. “Philosophers have noted that there are different kinds of impossibility (and thus possibility). First, something is conceptually impossible it is logically inconsistent. Second, something is physically impossible when it is inconsistent with laws of nature. Third, something is technologically impossible when it cannot occur given the current state of technology. The debates over de-extinction largely concern the first two notions of impossibility.”

8. Reviewer 1 also wonders whether notions of authenticity are even scientific. I have addressed this by adding the following sentence explaining the notion in more detail, “When we say something is inauthentic, we are saying either that it is not identical to the object of interest or it does not share many of the properties that the target of interest possesses (Siipi 2014, 77-78)” (p. 12). I have also added the following footnote on the same page; “A different sort of worry is whether authenticity is even a scientific notion at all. For an attempt to show how it a scientific notion, see Dudley (2012).”

9. The concerns over moral responsibility and passenger pigeons have been more fully addressed in the manuscript. In effect, Reviewer 1 wonders why those who did not kill passenger pigeons would be morally responsible for resurrecting or recreating them. Of course, I agree they might not be but there are circumstances where they would be. On p. 13, I added the following sentence, “Thus, Americans who benefited from their extinction (even if they did not drive them extinct) might owe them restitution through de-extinction.”

10. I have addressed Reviewer 1’s concerns regarding the argument from hubris. They worry that I have misrepresented the argument by suggesting it is simply the worry that proponents of de-extinction do not realize the technological limitations involved. That is one component of their objection. However, another component is that they seem to think any attempt at de-extinction is hubristic. But I claim that it is implausible since it would also rule out the use of any of the technologies involved in de-extinction. Thus, I have changed the paragraph on p. 16, “Third, if sound, this argument would suggest we should avoid all manner of technologies not the least of which is de-extinction. After all, cloning and gene editing alone are only the most dazzling of our current technologies but conservationists also use camera traps, tracking tags, remote sensing, acoustic sensors, drones, eDNA, and artificial intelligence. Should we avoid those as well because they may involve hubris?”

11. I corrected the grammatical mistake on p. 16, “After all, cloning and gene editing alone are only the most dazzling of our current technologies but conservationists also use camera traps, tracking tags, remote sensing, acoustic sensors, drones, eDNA, and artificial intelligence.”

12. Reviewer 1 requests that I provide reasons for why frozen zoos and seed banks are important. On p. 16, I added, “After all, if a species disappears “in the wild,” conserving tissue samples may allow us to prevent them from going extinct.”

13. They also asked me to rewrite the paragraph before the conclusion (p.16-17) since it was a bit confusing and had grammatical mistakes. I have done this. Here is that paragraph. “We can now take stock of the moral arguments for and against de-extinction. The general conclusion we have found is that it is morally permissible to resurrect or recreate species except when there are outweighing morally relevant considerations. These moral considerations concern animal welfare, hubris, and poor allocation of resources will sometimes outweigh obligations to recreate or resurrect species but not always. Thus, moral decisions regarding de-extinction will often need to be decided on a case-by-case basis.”

Let me now turn to Reviewer 2’s comments.

1. Reviewer notes that Campbell (2016) has an interesting discussion of inclusive definitions of de-extinction. I have added a footnote on p. 3, “For another discussion of inclusive definitions of ‘de-extinction’, see Campbell (2016).”

2. They also noted the argument discussed on p. 10 has a similarity to a discussion of Piotrowska. I have added the Piotrowska (2018) citation by writing, “But hybridization and horizontal gene transfer occurs throughout the natural world (Piotrowska 2018).”

3. They requested that I add the Cottrell, Jensen and Peck (2014) and the Lean (2020 citations in reference to the duties argument. On p. 13, I have added a footnote, “For further discussion of this type of argument, see Cottrell, Jensen, and Peck (2014) and Lean (2020).”

Recommendation: Philosophy and ethics of de-extinction — R1/PR7

Published online by Cambridge University Press:  30 January 2023
DOI: https://doi.org/10.1017/ext.2023.4.pr7 [Opens in a new window]
Kate Lyons School of Biological Sciences, University of Nebraska-Lincoln, United States
Revision round: 1
Role: Handling Editor
Recommendation/decision: accept

Comments

Comments to Author: Dear Dr. Odenbaugh,

Thank you for revising your manuscript to incorporate the suggestions of the two reviewers. I am happy to recommend it for publication.

Best wishes,

Kate Lyons

Decision: Philosophy and ethics of de-extinction — R1/PR8

Published online by Cambridge University Press:  30 January 2023
DOI: https://doi.org/10.1017/ext.2023.4.pr8 [Opens in a new window]
Barry Brook [Opens in a new window] School of Natural Sciences, University of Tasmania, Australia
Revision round: 1
Role: Editor in Chief
Recommendation/decision: accept

Comments

No accompanying comment.