Technological advances raise the prospect of altering human life as we know it in dramatic ways, and not just in the sense of changing the conduct of human life (as in the transitions from horse to rail to car), but perhaps also in the sense of changing the very nature of human life. Germ line genetic engineering is the most obvious route by which radical biological alteration might be fostered, but other new forms of technology are potentially relevant here as well, including cybernetics and nanotechnology. They may render possible not merely the correction of human infirmities (comparatively uncontroversial forms of intervention), nor merely the enhancement of our existing human nature (more controversial), but also the active direction of our own evolution and the rapid creation of a new “posthuman” species—or even sets of new species.

Such an idea is held out at least as a hope by some members of the so‐called posthumanist or transhumanist movement. Some take these terms as synonymous, while others draw more or less sharp distinctions between them (see Thweatt‐Bates , 3–13; Burdett , 3–6 for further discussion). For the remainder of this article, I will employ transhumanist.

The transhumanist movement is a diverse one, and not all self‐identified transhumanists look favorably on the prospect of leaving human nature behind altogether. Some focus instead on technological means of enhancing existing human nature. Yet others unambiguously favor taking the reins of our own evolution and making something genuinely novel. Max More (, 4), for instance, writes that “transhumanists want to apply technology to overcome limits imposed by our biological and genetic heritage. Transhumanists regard human nature not as an end in itself, not as perfect, and not as having any claim on our allegiance. Rather, it is just one point along an evolutionary pathway and we can learn to reshape our own nature in ways we deem desirable and valuable. By thoughtfully, carefully, and yet boldly applying technology to ourselves, we can become something no longer accurately described as human.” By contrast, theorists like H. Tristram Engelhardt () recoil from such a prospect; still others maintain that moral questions about whether and how to pursue human genetic enhancement are separable from questions about whether such enhancement might lead to the development of a new species. John Harris (, 37) argues that “if the gains were important enough (sufficiently beneficial) and the risks acceptable, we would want to make the relevant alterations…we would have an obligation to make such changes.…[W]hether any proposed changes amount to changes in human nature, or to involve further evolution, seems ethically uninteresting. In particular, whether the enhancements might be judged to involve creating a new species, ‘a new breed,’ or amount to ‘self‐evolution’ or ‘post humanism’ or ‘transhumanism’ are not moral issues.”

I do not wish to delve into those normative disputes here (at least not directly). Rather, I would like to examine what exactly is involved in the claim that we are in principle able to “transcend” human nature through the engineering of a new human species. This warrants further discussion, insofar as it is openly acknowledged by some in the transhumanism literature that there remains a lack of clarity as to what exactly this could mean. Gerald McKenny, for instance, writes,

Most of the literature assumes that it will one day be possible to deliberately alter human functions, traits and capacities by biomedical technology. This assumption is plausible, but it is difficult to determine what implications it has for human nature. Specifically, it is far from clear (1) which interventions would truly alter these functions, traits or capacities (in contrast, say, to having a temporary effect on them); (2) whether human nature itself or only these functions, and so on, would be altered; and (3) if human nature is indeed altered, whether the alteration would be to the human species or only to the individual human beings who have undergone the alteration(s). (McKenny , 19)

Similarly, McKenny elsewhere (, 171) asks: “Could some development in biotechnology—in genetic engineering, perhaps, or in neurobiology—alter human nature itself, so that those who undergo the technique or inherit its effects are no longer instances of the same natural kind or members of the same species as those who remain unaltered? Any answer to this question must begin by gaining clarity on what would count as an alternation of nature in this sense.” And McKenny goes on to argue that several recent proposed answers to this question fail.

Given this lack of clarity, it might be worthwhile to see what contemporary biology can contribute here. Of course, it is not obvious whether or how current science should impact our philosophical and theological thinking about transhumanism, since the relationship between scientific and philosophical accounts of “human nature” is itself a matter of contention. Certainly it would be controversial to claim that we can simply read a philosophical (let alone theological) account of humanity directly off the biology. Nevertheless, when faced with claims and counterclaims pertaining to the intentional alteration of Homo sapiens, it is not unreasonable to think that our best current science of species and speciation could have something important to say. Indeed, on some models of the science–religion relationship, we would be positively remiss in ignoring it. I am not of course the first to look at transhumanism through the lens of current biology—Nicholas Agar (, ch. 2), for instance, provides a discussion of how current biological theories of species and speciation intersect with the debate over radical genetic enhancement. But theological discussions of transhumanism have seen relatively little detailed engagement with these accounts.

The remainder of this article is divided as follows. In the section titled “A Quick Primer on Modern Biological Taxonomy,” I provide a brief primer on species concepts and speciation in contemporary biological taxonomy. “Implications for Technological Alteration of Species” sees the drawing out of some implications for the prospects of our being able intentionally to intervene in human evolution for the production of new species out of Homo sapiens. The section titled “How Does the Biological Conception of Homo sapiens Relate to a Philosophical (or Theological) Account of Human Nature? And Where Does This Leave Transhumanism?” then brings in the debate over the proper relationship between biological and theological conceptions of human nature, presenting some of the major options and illustrating some of their possible implications for our understanding of transhumanism. “Potential Applications to Specific Subdisciplines of Theology” sees the examination of how some of those models find application in different areas of theology (specifically hamartiology, soteriology, and eschatology) and their relationship to transhumanism. Finally, in the concluding section, “Suggestions for Future Work,” I briefly lay out some recommendations for future work, focusing on tasks that theologians specifically ought to pursue.

A QUICK PRIMER ON MODERN BIOLOGICAL TAXONOMY

“Taxonomy” refers to the theory and practice of classifying organisms. Looking out at the vast range of organisms in nature, and noting assorted commonalities among them, the taxonomist seeks to categorize these organisms into types arranged in a hierarchy of generality (species, genus, family, and so on). In current biological taxonomy, there is an important divide between two perspectives on classification: phenetic versus phylogenetic. In phenetic classification, organisms are categorized on the basis of statistically calibrated phenotypic similarities (i.e., similarities in observable characteristics like physical structure, blood type, metabolism, and so on). By contrast, in phylogenetic classification not all similarities are admissible for use in classification; rather, only those similarities resulting from common ancestry (lineal descent) should count. There are different schools of thought within phylogenetic classification (e.g., evolutionary taxonomy vs. process cladism), but for present purposes the debates between those subdivisions can be left to one side. (For a thorough yet accessible introduction to the major versions of phylogenetic taxonomy, consult Ereshefsky , 50–79.) However important those debates may be, they involve disagreements the depth and import of which remain comparatively minor when compared to the fundamental split between phenetic and phylogenetic ways of doing taxonomy.

For present purposes, it is important to note that today the great majority of taxonomists operate in accordance with the phylogenetic perspective. This is reflective of the centrality of evolutionary theory in modern biology. Organisms are classified in accordance with their location on the evolutionary tree of life. As such, the placement of an individual organism in a certain species requires that that organism find its immediate ancestors in that same species (just as the placement of a species in a certain genus is based on facts about common ancestry, as is the placement of a genus in a family, and so on). This is a substantial departure from pre‐Darwinian taxonomy, in which the goal was to classify organisms in accordance with their intrinsic essences. These essences, conceived along broadly Aristotelian lines as underlying substantial forms, manifested in the outward traits catalogued by anatomists (in fact catalogued in a manner roughly analogous to the cataloguing done by modern pheneticists).

To draw out the contrast: in pre‐Darwinian taxonomic theory, a cat, an individual member of the species Felix catus, is a member of that species because of its intrinsic essence. That essence manifests itself in the morphological, behavioral, and other features characteristic of members of this species. Traditional versions of intrinsic biological essentialism (INBE) are ahistorical, in the sense that if we travelled to Mars and found organisms identical in all these respects to cats on Earth, we could legitimately take them to be cats. Similarly, if tomorrow God were to create ex nihilo an animal with the same sort of intrinsic essence as existent cats, INBE would label them all as members of that species. By contrast, neither the Mars‐cat nor the new ex nihilo “cat” would count as legitimate cats according to the majority phylogenetic perspective operative in modern biological taxonomy: something is a cat only if it is descended from prior members of Felix catus. Lineal descent is a necessary condition on species membership. The Mars‐cat may be a very similar organism, and may even be capable in principle of interbreeding with Earth‐cats. However, because it does not belong to the same lineage, it is not a member of the same species. “Species” is an irreducibly historical category.

In this respect, Agar's (, ch. 2) discussion is somewhat out of step with the current majority position in biology. Agar takes the view that species membership is dependent chiefly on the capacity to interbreed, such that shared lineage seems not to play much of a role, even as a necessary condition. See especially his thought experiment (Agar , 23–24) concerning the transformation of an individual member of Homo sapiens into a member of Homo neanderthalensis. Such a scenario would in fact be seen as impossible by most biologists: one can radically alter one's physical appearance or even genetic code, but one cannot alter the past historical facts of one's ancestry, and so a single individual cannot join another biological species.

Yet Agar's misstep on this point is entirely understandable; indeed, the conception of species as a historical category can initially seem highly counterintuitive. Many are inclined to think that the hypothetical Mars‐cat really would be a cat, if indeed it had the identical type of genetic code, morphology, behavior, and so on. But the historical conception of species is very much entrenched in contemporary biology, in part because of longstanding problems facing traditional versions of INBE. (For discussion of standard criticisms of INBE, see, for instance, Mayr , ; Hull , ; Sober ; Dupré ; Ereshefsky , 95–102, ; Ellis , 29–30; Stamos .) Of course, as already noted not everyone views taxonomy in this way; pheneticism retains advocates, and there has even been something of an attempted revival of INBE in theoretical biology and philosophy of biology. (See, for instance, Kitts and Kitts ; Wilkerson ; Webster and Goodwin ; Walsh ; Oderberg ; Devitt ; Elder ; Dumsday , .) However, even that latter revival is to a degree muted, insofar as some of its proponents argue for a nontraditional, moderate version of INBE. On this version, organisms have intrinsic essences, but those essences do not suffice for species membership, with lineage still playing a necessary role in classification. In other words, on moderate INBE species membership is derived from lineage + intrinsic essence, rather than only the intrinsic essence (as on traditional INBE), or only lineage (as on phylogenetic classification). Devitt () and Dumsday () incline toward moderate INBE, and arguably so do some other neoessentialists in the philosophy of biology.

The key point for present purposes is that, while there remains some dissent, the large majority of those working in theoretical biology and philosophy of biology (as well as the large majority of working taxonomists) view lineage as at least a necessary condition for species membership—and a smaller majority would go even further and identify lineage as necessary and sufficient for species membership.

Taking on board the assumption that lineal descent is at least a necessary condition for species membership, it follows that plausible models of speciation (i.e., models of how new species arise) will have to involve branching lineages. Unsurprisingly, the most prominent model of speciation in current biological taxonomy, allopatric speciation, works in just that way. Marc Ereshefsky summarizes,

The allopatric model of speciation is the most prominent account of speciation for sexual organisms. It states that speciation begins when a population becomes geographically separated from its parental species. Speciation is complete when such a population is reproductively isolated from its parental species. The members of a new species, in other words, must acquire reproductive isolating mechanisms that prevent them from interbreeding and producing fertile offspring with the members of its parental species. Reproductive isolating mechanisms come in two forms. Prezygotic mechanisms, such as incompatible sexual physiologies, prevent members of different species from mating. Postzygotic mechanisms stymie the development of viable offspring after mating. (Ereshevsky , 718)

Much more could be said by way of expanding on current conceptions of species and of speciation, but hopefully the preceding bare‐bones summary will suffice for our limited purposes.

I should, however, briefly draw attention to three complicating factors I have up until now left aside:

• (1)

  First, the preceding discussion has taken for granted that when we are talking about “species” we are talking about a single, objectively real (in some sense) explanatory factor in nature. And this is indeed how it is most commonly regarded in biology and philosophy of biology. Species are typically seen as the basic units of evolution, and insofar as evolution is a real process, species are the real elements figuring in that process. Still, this common perspective is not universal; some regard the species category, as understood by most contemporary biologists, as flawed in important ways and not objectively real in the way typically thought. Note that the dispute here concerns how to think about the species category, not how to think about individual species taxa. Everyone agrees that there are cats and people, such that Felix catus and Homo sapiens are both real as empirically observable reproductive communities. The question is whether these taxa belong to some single, objectively real overarching category known as “species.” Most would say that they do, but a good many others advocate pluralist rather than monist conceptions of the species category, such that they think there are multiple legitimate conceptions of what it is to be a species (with differing versions of pluralism arising partly from further disputes about where the boundaries of legitimacy are drawn), and still others advocate a sort of antirealism with respect to the species category. The stance I have adopted here is the prevailing monist, realist, and broadly phylogenetic perspective. But the presence in the literature of alternative understandings should be kept in mind, and I will have a bit more to say about the possible theological import of these in “Potential Applications to Specific Subdisciplines of Theology” below.

• (2)

  Second, acceptance of the unity and objectivity of the species category should not be taken to imply that there is no room left for vagueness or indeterminacy with respect to an individual organism's or population's membership in a species taxon. That is, one can adopt a precise understanding of what it is to be a species, while admitting uncertainty about whether some organism or interbreeding community does or does not belong within a particular taxon. Disputes and shifts in thinking need not be taken as undermining the reality and objectivity of the species category, or its important explanatory role in evolutionary theory. In fact, disputes about borderline cases and potentially indeterminate classifications are common in discussions of natural kinds, not just in biology but across the sciences; think, for instance, of discussions in philosophy of chemistry about the status of isotopes or the products of certain complex chemical reactions. (For an accessible entry point to the literature concerning vagueness in the metaphysics of natural kinds, see Hawley and Bird .) That there are such disputes need not be seen as evidence that the species category is lacking in objectivity, or that the question of membership in a particular biological taxon is merely a matter of semantics. On the contrary, that such disputes are common throughout the sciences (and philosophy of science) indicates that scientists tend to think of classification as aiming at an objective “carving of nature's joints,” one worth disputing about precisely because facts about the natural world are at stake.

• (3)

  Third, while I have mentioned higher taxa (genera, and so on), the main focus so far has been on species. This is reflective of the far greater attention given to the species category in the existing literature, both in biology and philosophy of biology, which attention is in turn reflective of the special status commonly accorded species as the units of evolution. It has commonly (though not universally) been held that the higher taxa are mere conceptual abstractions, not real in the same way (or, alternatively, not real to the same degree) as species. For instance, Niles Eldredge and Joel Cracraft (, 249) write, “That taxa of categorical rank higher than species do not exist in precisely the same sense as do species is crucial.… What all taxa, from species up through kingdoms, do share is presumed descent from a single ancestral species. What they do not share are similar reproductive patterns” (quoted in Ereshefsky , 85). A detailed treatment of this issue would take us well beyond the central concerns of this article, but the debate over the ontological status of higher taxa is worth keeping in mind, for a reason that will be made apparent in the section “Potential Applications to Specific Subdisciplines of Theology” below.

IMPLICATIONS FOR TECHNOLOGICAL ALTERATION OF SPECIES

A hypothetical transhumanist scientist wishing to produce a new species out of the parental Homo sapiens would have at least two available routes: a relatively easy but slow route, or a more technologically involved but faster route. As to the first, she could, for example, isolate a human population from the rest of the species (a Mars colony perhaps?), subject it to dramatically new environmental pressures, and leave it in isolation for thousands of years with the hope that new mutations will gradually alter the isolated population in ways that render its members physically incapable of interbreeding with the rest of humanity (either because of prezygotic or postzygotic incapacity). This method of getting to a new “human” species is relatively easy from a technological perspective (especially, if one changes the hypothetical example from a Mars colony to an Antarctic colony), but also uncertain and lengthy. (Human populations living on remote islands, isolated from the rest of humanity for thousands of years, nevertheless obviously remained part of Homo sapiens.)

Another route, more difficult from a technical standpoint, would be to engage in some dramatic germline genetic engineering, thereby producing a new class of people reproductively isolated from the rest of the human population. Again, there are various ways this might be accomplished—one can, for instance, envisage a scenario in which genetic engineering produces a hyperintelligent subclass, which chooses only to interbreed among its own members, such that, over time, mutations occur unique to that population and eventually they are rendered physically unable to reproduce with the larger population and a distinct lineage begins. That too would be a lengthy process, however. More immediate and dramatic would be genetic interventions to produce directly a class or classes incapable (whether due to prezygotic or postzygotic mechanisms) of reproducing with the larger human populace yet still capable of reproducing among themselves. Such interventions could conceivably involve substantial outward phenotypic alterations (here one inevitably thinks of science fiction examples), but they need not. One can, for instance, hypothesize the creation of a class of individuals largely equivalent in outward appearance to “normal” humans yet capable of reproducing fertile offspring only among other members of that class. I am not competent to comment on the actual feasibility of this prospect given the current state of knowledge in genetic engineering, but it seems difficult to rule out in principle. (Here a referee has helpfully drawn my attention to ongoing work on the human artificial chromosome [HAC], the product of a technique for introducing a new chromosome into a zygote; such a technique has been used successfully in bacteria and yeast for 20 years, and progress toward human trials has been rapid. It is certainly one method by which some fairly dramatic changes might realistically be introduced into the human reproductive process in the near future. For an accessible introduction to the HAC, see Dvorsky .) Why one would want to create such a class is of course another question entirely—again, one's mind inevitably turns to science fiction, in this case perhaps Aldous Huxley's Brave New World.

From the preceding, we can draw the important conclusion that under the currently prevailing conception of speciation for sexually reproducing organisms, technological intervention to create a new biological species (i.e., a new lineage reproductively isolated from the previous) out of Homo sapiens is both easier and more difficult than one might suppose at first glance. It need not require substantial changes to outward phenotype, and indeed if one is willing to wait long enough, mere geographic isolation, under certain conditions, could theoretically do the trick. On the other hand, if one wants to bring about the rapid formation of a new, isolated lineage, genetic engineering would indeed be required to prompt the relevant changes in reproductive capacity, though again, in theory that need not involve substantial changes to the outward human form.

Of course, a considerable portion of the transhumanist literature is concerned less with the engineering of new biological species out of Homo sapiens, and more with the overcoming of biology by way of merging us with machines, whether partially (cyborgs) or wholly (uploading human consciousness into a computer, thereby leaving biological life behind entirely). With respect to partial merging, if these cyborgs still engage in sexual reproduction and do not form among themselves a new, reproductively isolated lineage, then biologically speaking they remain full members of Homo sapiens (however many extra robot limbs and so on they may have acquired). Again, from the perspective of modern biological taxonomy, a new species will be present only if a new lineage is present. While one can certainly imagine scenarios in which this partial merging contributes to the forming of a new species (e.g., a scenario in which cyborgs refuse to mate with noncyborgs, such that over time accumulated mutations result in reproductive isolation), it need not have that result. By contrast, transhumanist scenarios involving complete merger via the hypothetical uploading of consciousness into a computer would take us beyond the realm of biology altogether. If all people left their bodies behind and uploaded into computers, Homo sapiens would cease to exist as a biological species.

HOW DOES THE BIOLOGICAL CONCEPTION OF Homo sapiens RELATE TO A PHILOSOPHICAL (OR THEOLOGICAL) ACCOUNT OF HUMAN NATURE? AND WHERE DOES THIS LEAVE TRANSHUMANISM?

To help us reflect on how the preceding biological account of species relates to philosophical and theological accounts of human nature, and in turn how different models of those relationships might impact transhumanism, I would like first to take a cue from three elements of Ian Barbour's (, ) well known (though arguably somewhat dated) categorization scheme. His scheme pertained to the major competing views concerning the relationship between science and religion, but it can be translated readily enough into the present context.

POTENTIAL APPLICATIONS TO SPECIFIC SUBDISCIPLINES OF THEOLOGY

SUGGESTIONS FOR FUTURE WORK

That there is considerable work to be done by theologians in this context will be clear from the preceding two sections. And perhaps that material has already sparked some ideas regarding possible lines of further inquiry; that was the primary intention, for I have certainly not done much of anything by way of answering those questions. Still, I will conclude by leaving the reader with a few further suggestions:

• (1)

  Theologians currently in dialogue with the transhumanist movement are already well aware of the variations present in the latter; to restate a point raised in the beginning of this article, some transhumanists favor human enhancement within existing human nature, while others favor the intentional development of one or more wholly new species. In their discussions with transhumanists of that latter stripe, it is especially important to clarify what conception of human nature the transhumanists are working with, and thus what they think they will be leaving behind when the “posthuman” future has emerged. One cannot assume that a particular transhumanist views human nature as identifiable with, or reducible, to the current biological account of Homo sapiens. In principle, transhumanism (even secular transhumanism) could be combined with any number of philosophical or theological conceptions of human nature. (Indeed, those transhumanists who think that we will remain human even after uploading our consciousnesses into computers are clearly not identifying human nature with Homo sapiens.)

• (2)

  Correspondingly, theologians engaged in discussion with transhumanists should have a clear idea of which philosophical/theological account of human nature they favor; moreover, if that account differs from the account put forward in contemporary biology, they should likewise have a clear understanding of how they view the relationship between the two. (Arguably it need not—one could make the case that it is open to the Christian theologian simply to identify human nature with the Homo sapiens of contemporary biology.) It would be difficult to overemphasize the importance of these two points, given their potential implications for one's understanding of trans‐humanism. Of course, this will inevitably involve theological and philosophical complications, insofar as Christian theology at least arguably lacks a dogmatically defined, detailed account of human nature; in fact a range of views can be seen across Church history, both across denominations and within denominations. For instance, while some Roman Catholic philosophers and theologians assume that Catholicism has ensconced a version of Aristotelian hylomorphism, this is in fact debatable; moreover, even if true, there are a variety of importantly different versions of hylomorphism—for example, the Thomistic, Scotisic, Suarezian, and so on. Ideally, a Catholic dialogue with transhumanism would (after first clarifying the version of transhumanism on offer) specify carefully the metaphysics of human nature adopted by the Catholic interlocutor—for example, Scotistic hylomorphism—and how that metaphysics relates to the account of Homo sapiens presented in contemporary biology. With all that groundwork in place from the outset, mutual understanding between Catholic theologians and secular transhumanists might be more easily achievable, even if ultimate agreement on, for instance, normative questions remains elusive. Although perhaps even the moral debates might be illumined by that careful preliminary work. (For a recent example of how the careful articulation of a specific theological anthropology can contribute to a more productive engagement with transhumanism, see again Thweatt‐Bates .)

• (3)

  In the previous section, I brought in another major world religion, Hinduism, to illustrate a conceptual point. That was of course quite a limited and superficial interaction with Hindu theology. Ideally Christian engagement with transhumanism should be informed by an ongoing dialogue with other faiths, and a careful observation of the ways in which scholars from those faiths engage with transhumanism.

ACKNOWLEDGMENTS

A version of this article was presented at a workshop on theology and transhumanism in April 2016, funded by the John Templeton Foundation. I would like to thank all those in attendance for their comments, and of course the JTF and the event's organizer, Michael Burdett, for the kind opportunity to speak. I would also like to express my thanks to two anonymous referees for Zygon: Journal of Religion and Science for their many helpful comments on an earlier draft. Finally, I should note that the initial portions of the section “A Quick Primer on Modern Biological Taxonomy” have appeared in publication previously, in my article “How Modern Biological Taxonomy Sheds Light on the Incarnation” (Journal of Analytic Theology 5:163–74). Thanks are due to Makmiller Pedroso, Fr. Joachim Ostermann, and Joseph LaPorte for their generous assistance with that work.