A number of influential biologists are currently pursuing efforts to restore previously extinct species. But for decades, philosophers of biology have regarded “de-extinction” as conceptually incoherent. Once a species is gone, it is gone forever. We argue that a range of metaphysical, biological, and ethical grounds for opposing de-extinction are at best inconclusive and that a pragmatic stance that allows for its possibility is more appealing.
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Some, but certainly not all, as we discuss in more detail in “Species concepts: a pragmatic, pluralistic approach” section and “The pragmatic context for de-extinction” section below.
Advocates of the Species-as-Individuals (SAI) approach to species might object to our talk of membership and instantiation as opposed to parthood (Ghiselin 1987). For now, they are invited to substitute a congenial replacement (such as ‘part of’); we address SAI directly in “Individuality and de-extinction” section.
Some writers spend more effort attempting to square the various restoration projects falling under the broad umbrella of ‘de-extinction’ with this line of thought (Siipi and Finkleman 2016); since we are not much persuaded by the arguments behind this position, we will not comment on these alternative conceptions of ‘de-extinction’. If, on your view, de-extinction implies finality as a matter of conceptual necessity, then you may think of the question of this paper as whether if all the members of a species should die, whether new members of that same species might later come into existence.
We might consider an analogy to the elements. Suppose that a synthetic element Xnium is produced using means that make it very unlikely that we should ever see any more of it. As is typical of heavy elements, it quickly decays. No more Xnium. Now there is plausibly a sense in which the kind Xnium (defined by its atomic number: say, 119) persists—the sense in which if (against all odds) one made some more stuff with atomic number 119, it would be Xnium. But it would be rather misleading to say (after the few atoms of Xnium have vanished and the means of producing it no longer available) that there is still Xnium, that Xnium exists. This is “extinction” enough of us; after all, it is the kind of extinction that is relevant to the prospect of a given species evolving or interacting causally with other species.
Now, one might argue that the watch does not go out of existence but rather remains in pieces on the repair bench (or wherever its pieces are scattered). But in either case, we have spatiotemporal scatter—either in the spatial or temporal dimensions—putting pressure on the claim that species are spatiotemporally restricted.
This concept, of course, can also be interpreted in different ways. Does it apply, for example, in a case in which a single cell is preserved of a multicellular organism that is subsequently “regrown”? Would it apply if all we have is a strand of DNA? We will address such questions below.
Indeed, one might even explicitly prepare for a de-extinction attempt as a contingency plan for species that are particularly threatened.
Siipi and Finkleman (2016) advocate for an “operational” interpretation of the BSC that requires conspecifics be able to “actually interbreed” with each other, thus entailing that de-extinction is conceptually impossible on this interpretation of the BSC (2016, p. 5, notes 2 and 3). This strikes us as an overly demanding interpretation of operationality (note that, strictly interpreted, it would require that two organisms of the same sex or two organisms separated by an appreciable number of generations could not be regarded as conspecific either). We leave this issue to one side in the present context. We will essentially agree with the broader point that Siipi and Finkleman make that whether we regard de-extinction as possible will depend on how we conceptualize species.
According to which species are defined by their occupancy of a particular ecological niche (van Valen 1976).
One might also pressure advocates of the ESC to be more specific about the kind of ecological role that is constitutive of species identity, putting pressure in turn on their compatibility with de-extinction. For example, is it supposed to be a purely functional matter whether a population fills a particular ecological niche or need the relationship make reference to other particular species (in which case, perhaps, a holism might apply)? We are not sure what defenders of the ESC would want to say here and leave the matter open; thanks to Ken Shockley for raising this question.
Clearly more needs to be said on this matter (here we are grateful to Maureen O’Malley’s feedback); granted, it seems unreasonable to simply presuppose “Star Trek”-esque technology (Heisenberg Compensators ≈ Epigenetic Compensators?), but nor is it obvious to what extent one ought to supply a technical “how possibly” account of the relevant background.
Godfrey-Smith (2009) argues that even this weaker requirement of material overlap is too restrictive because it rules out cases of formal reproduction, such as when a virus reproduces using only the machinery of its host cell.
Our pragmatic approach to the relevant conceptual tolerances for causal connection might also be brought to bear on the question we left aside above of whether the HPC account of natural kinds might apply to putatively resurrected species—viz. whether the same homeostatic mechanism was responsible for the stability of a property cluster associated with a species taxon exhibiting a temporal gap in those properties’ instantiation.
Thanks to an anonymous referee for bringing our attention to this document.
Similarly vague turns of phrase occur elsewhere in this debate; M.R. O’Connor, for example, asks at the outset of her popular treatment of Resurrection Science: “Is a bird born of human ingenuity in the laboratory the same as a bird born of natural selection in the wild?” (2015, p. 8; our emphasis).
Elliot (1982, p. 85) draws on a similar analogy to argue that ecological restoration projects, such as the reconstruction of a dune destroyed due to mining, often fail to restore the full value of what was lost.
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A shorter, ancestral version of this paper was presented by MHS at the 2017 Pacific APA in Seattle, WA and in the “Classification in Biological Practice” workshop organized at the Vrije Universiteit Amsterdam in April 2017. MHS is grateful to participants in both audiences for helpful comments and questions on those occasions and in particular to David Ludwig, Maureen O’Malley, Thomas Reydon, and Ken Shockley; Matt Barker and Neil Williams also provided helpful written comments on a subsequent draft. HC was the commentator assigned at the APA whose constructive comments and extensions were subsequently collaboratively woven through the paper as a new, joint version. The paper is thus fully collaborative.
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Slater, M.H., Clatterbuck, H. A pragmatic approach to the possibility of de-extinction. Biol Philos 33, 4 (2018). https://doi.org/10.1007/s10539-018-9615-5
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