Introduction
Although many are less willing to accept that nonhuman animals have no moral status, the argument that animal research necessarily benefits human health has been harder to dislodge from common ideologies. Footnote 1 For example, in a striking letter led by the naturalist David Attenborough, it was claimed that alternatives to primate neurological research made such experiments redundant, Footnote 2 but more so, the issue was that they were cruel. Footnote 3 In response, a number of eminent scientists wrote that primates provide an invaluable model for human neurology, and that, therefore, continued research offered the only hope for people with neurological disease. Footnote 4 They supported the position, stated elsewhere, that the benefits of animal research are “utterly beyond quantification” and “incalculably great,” Footnote 5 and specifically to my present enquiry, necessary for the “significant advancement of neurosciences.” Footnote 6
It is in this context that the National Institutes of Health (NIH) has undertaken a public consultation on releasing prohibitions on funding for chimeric research, Footnote 7 including where there “could either be a substantial contribution or a substantial functional modification to the animal brain by the human cells.” Footnote 8 In the background of the NIH moratorium are the metaphysical and ontological claims about what a chimeric being would be. At a practical level, this raises questions about what to do with a chimera if it were found to be “human,” or to have capacities—something like “human consciousness” Footnote 9 —that arguably give us our ostensibly distinct moral status. Moral consistency would suggest that if a chimera were to become conscious to the degree that humans are, then we would have to consider its rights seriously (if indeed that is the grounds for moral status; and putting to one side, in this article, advocating rights for all animals). However, because of the challenge of understanding mind in animals, there is a tendency for policy to dwell on the “gray zones” in animal ethics; that is, to avoid such perplexities, to thereby find a supposed middle ground around the opportunities for discovery and health advances.
In this article, an experiment to create a human-brain model in a mouse is described. I examine the professed theoretical rigor that substantiates conducting the experiment, and which alleges that it is ethical. Footnote 10 I reject this conclusion, not in terms of whether benefits are possible or inevitable, but by arguing that if the purpose of an experiment specifies an analogue to human brain function, then it is logical that those experiments are conducted with human patients. That deduction is based on the possibility that a chimera is “conscious” to the extent that its interests matter, and if that kind of “consciousness” is not plausible, then neurological study of that model as analogous to human bioanatomy is flawed. My intention is to track the methodology of the “human-neuron mouse” experiment, and then to try the same experiment in a chimpanzee, because logically, that is likely to create a better model of human neurology. However, I argue that making the assertion that a chimeric mouse cannot possibly develop morally relevant properties must also be true for a similarly altered primate. Therefore, these models are concurrently improbable representations of the kinds of neurology that matter (therefore, chimeras with “human brains’’ likely have no morally important mental states, and therefore a nonanalogous brain). If, instead, these chimeras are plausible models of human neurology, then they are plausible moral beings, and that possibility makes the case for conditional reasons to ethically prefer human experiments. Such an approach would not risk the prospect of an abject existence of confined and experimented-on agential beings, a categorically more important reason to preclude such experiments. Footnote 11
My dispute, in this respect, is with those who argue categorically for chimera research, convinced by the essentialism of animal research and the expectation that scientific discovery will meet the urgency to alleviate human suffering. Footnote 12 This strategy has become a self-evident justification; and it is that certainty that I dispute here. Footnote 13 Simply stated, there are stronger moral reasons than lost scientific opportunities (and these can be gained elsewhere), to reject such experiments. Although my argument might be perceived as being against all animal research, that is not my intention. Instead, my modest claim is that insofar as the possibilities of creating chimeric mice make for beneficial research, the justification for the experiment obscures a more reasonable argument for investing in human brain research. Footnote 14
The Weissman Mouse
In 2002, the Stanford scientist Irving Weissman suggested creating a living mouse that would have something like a human brain. Footnote 15 In the proposed experiment, neonatal mouse neurons would be cleverly replaced with their human counterparts in situ, leaving the rest of the murine architecture ostensibly unaffected. This would result in something like a human-neuronal system: a functional brain organ in a mouse, which would allow the invasive study of human diseases outside of human patients. Footnote 16
Chimeras are not new to science, and most jurisdictions allow this research to some degree. Commentators remain divided about the salient ethical points of transferring human tissue into an animal or vice versa. Footnote 17 Some contend that such creatures create “moral confusion.” Footnote 18 Others say it crosses a Rubicon between species boundaries and thus violates integrity or dignity. Footnote 19 However, the hullabaloo about Weissman’s experiment stemmed from the anticipation of creating a human-like mind in a nonhuman animal. Footnote 20 That observation forces the question of whether Weissman’s chimera might be a moral agent. Footnote 21
At approximately the same time that Weissman proposed the experiment, he turned to his colleague, Henry “Hank” Greely, and asked him to consider the pertinent ethical issues. Greely set up an ad-hoc working group to advise the Stanford Medical School (“the Report”), as to whether to allow Weissman to create the “human-neuron mouse” (hereafter, the Weissman mouse). Footnote 22 Greely’s group suggested that the experiment could proceed ethically, but were more cautious about the risks of viral crossover and the breeding of the experimental animals, and recommended steps to avoid contamination of the food chain. In their particular assessment, “humanization” was not “plausibly raised”; Footnote 23 or, it was so remote that there was no reason to preclude such research. It was presumed that the mouse is somehow too different—because of its brain cavity size, or the presence and absence of other biological architecture—for it to adopt any higher capacities. In experiments in which human–animal chimeric brains have been created (often with less than total cell replacement), it has been claimed that there has “been nothing like a mouse with human thoughts”; Footnote 24 and, therefore, little evidence of transfer of “emergent human mental capacities.” Footnote 25 Weissman is an author on an article that confirms, to their satisfaction, research to date showing that “humanization” of cognitive capacities is not possible in the mouse brain. Footnote 26
For my purposes, I will focus on Greely’s assertions as a member of the Stanford group, and also in his opinions stated elsewhere that presumably informed that ethics review. According to the Report, the justification for the experiment rests on scientific opportunities. Such experiments, Greely explains, are “politically significant,” however, to the extent that some kinds of animal research might raise “public concerns,” especially where there is little economic or scientific advantage to outweigh those fears. Footnote 27 In the Report, it says that the risks that “animals with some possibility of human-like cogitative abilities” could be created required strict scientific justification, Footnote 28 so that “[d]isquieting or disturbing results at one stage should lead to discontinuance of the experiments pending further review of the ethical implications of those results.” Footnote 29 Weismann’s fail-safe (in addition to the Report’s conditional pause) is to kill and autopsy the animals to see if there are novel structures that suggest “humanization.” Although the Report itself confines its conclusion to the mouse experiment, Greely additionally considers the same experiment in great apes, admitting, perhaps, that this would be a better model for conducting experiments on human-like consciousness. Footnote 30
But what if the possibility of human consciousness became reality? The methodological problem is that that reality is unknowable, and policy really needs to consider what it would be like if Greely and the Report were wrong. Human experiments are bound by ethical conditions that prohibit invasive research that is nonconsensual (without a “best interests” rider) or unconscionable. Unethical clinical research, in this respect, is not a question of human welfare (therefore, is not comparable to the alternative framing in animal research), but is grounded in moral status. In one reading of moral consistency, then, if the possible happened—the chimera developed “human consciousness”—then the only way to continue with research (and not treat it as a person) would be by taking ownership of speciesism. Footnote 31 Greely seems to do just that (see subsequent discussion). However, what is more, he also claims that if we want to reap the benefits of human neurological sciences, then it makes ethical sense to turn to analogues of those systems. This becomes a “powerful reason” Footnote 32 —one that is necessary and exceptional—because the greater risk comes from obstructing potentially important discoveries. The point might be put differently: because the human brain is protected by moral (and regulatory) baggage, there is an authority in economic and practical rhetoric that dismisses perhaps remote, but logically possible, implications. Footnote 33 The trick in doing so is to count only the benefits to (and interests of) humans, while eschewing the pains that befall animals. Footnote 34
Neuroscience, Animal Research, and Chimeras
Greely argues his case with some caveats. One of these is that he suggests that the intent of Weissman’s experiment is in the realm of basic science, so that changes in murine consciousness are not intended by Weiessman. In fact, Greely writes that if that were intended, then one would better “go directly into clinical experiments with humans.” Footnote 35 One might easily dismiss his proviso with the risks of unintentional occurrences or accidents (it might be argued that one does not have to intend to do something—in this case, unpick the mechanisms of human consciousness—for something, that is “higher consciousness,” to appear, in an experiment). Footnote 36 However, that argument requires hedging on probabilities, and that is something that Greely has addressed to his satisfaction. Footnote 37 Instead, Greely’s premise is that the cellular or biochemical properties of human cells under investigation are not the vehicles of human consciousness (and cannot be studied by way of this experiment), so that converting a mouse to a “conscious” state is seemingly impossible.
But what if the experiment were to deliberately seek out a “thinking chimera”? Footnote 38 In this case, the assertion of improbability might be wrong to the extent that the experimenter admits that it is possible. It is my contention, therefore, that shifting justification from benefiting of human lives, Footnote 39 to adhering to moral consistency between known human states and possible chimeric states, raises doubts as to whether the experiment is at all ethical to conduct.
It is argued in the Report that the mouse experiment is justified because the induced, organic changes intended result in “human” characteristics: biological representations of human neurology. At the same time, it is alleged as well that it is implausible for these changes to result in anything that is “too” human. The Weismann mouse, therefore, is an ideal model because its lacks capacity pro tanto for “human consciousness,” and without that possibility, it is not morally abhorrent to imagine the experiment. The (circular) assertion appears to be that, on the one hand, human consciousness is known to be unique, and that rules out some kinds of invasive research on human beings. On the other hand, the unknowns of a human–animal brain model make the experiment ethical, yet still analogous. Therefore, at the same time, it is a scientifically prudent model of human neurology, yet simultaneously, it is an “implausible” model of human consciousness. Larry Carbone writes of this kind of justification: “In other words, animals must be sufficiently different from humans in morally relevant ways to allow the morality of speciesism, and animals must be sufficiently similar to humans biologically for cross-species extrapolation to have unity.” Footnote 40
One can add to that peculiar dichotomy the human–animal chimera.
The “Weissman Chimp” Experiment Footnote 41
There are two curiosities in Greely’s reasoning that suggest to me that he has not done enough to provide moral consistency. By this I mean that his group of claims cannot be rationally adjudicated in a nonquestion-begging way. There is one claim in particular: that the purpose of the Weissman mouse experiment is to create a biologically human, functional neuronal system that is not “too human.” That does not do enough: we still have to ask will that system be “human”; that is, will the morally important features of human agency be transferable to a nonhuman being?
Even with the most charitable interpretation, one would require some kind of consistency in Greely’s claim (that is repeated in the Report). One basic proposition Greely asserts is that human consciousness matters; however, it also matters, according to him, that scientists are permitted to create conditions that, for all we know, cause human consciousness in another being. Footnote 42 Therefore, consider conducting the same experiment in a chimpanzee, whose evolutionary, morphological, behavioral, and cultural closeness to us make them both a useful research model, and an ethically problematic one. The arguments against primate research are well rehearsed: the “costs of laboratory-caused trauma are immeasurable in their life-long psychological impact on, and consequent suffering of, chimpanzees;” Footnote 43 and “most current use of chimpanzees for biomedical research is unnecessary” that speaks to the disputed moral imperative of such research as well as the alternatives. Footnote 44 There might be methodological reasons that are against primate research as well: mice are relatively easy to manipulate and to physically handle, engineered breeds are already available, and research facilities are less costly. There are also the sociopolitical reasons: few care about mice in the same way as they do about primates—the NIH or Royal Society create few hurdles to conducting research with them Footnote 45 —and that is likely because primates are (or are perceived to be) morally relevant at least because of their evolutionary, behavioral, and anthropomorphological similarities. Most of all, “human-like chimps” would likely cause a great kerfuffle for public relations. But these reasons have little bearing on the weighted benefits approach used to define the acceptability of the mouse experiment, because that was also an argument based on fidelity; that is, animal experiments can be sufficiently relevant to human neuroscience, and neuroscience is inherently worthy. Footnote 46
Therefore, if “humanization” is at least possible in the mouse (otherwise why study it?), then the same experiment in the chimpanzee might reveal a creature more like a human, and, therefore, one better to study. Not only are the factors that limit the possibility for an altered murine mind, such as cranial size or neural support structures, irrelevant in the chimpanzee, but also the chimpanzee looks like us (which enables us to arguably “read” its mind through symbolic cues); and, because higher primates have capacity for complex sociality, these might mimic mental diseases of “the human condition” better. Footnote 47 Most of all, we know what human disease looks like, and that might be more relevantly shown in our closest relative. Accepting these points, one can perhaps reimagine the Weissman experiment as a way to tease out the most complex attributes and abilities of human neurology. And if the “human benefits” argument has moral weight, then the practical impositions of primate research on this basis could be overcome: protagonists would simply have to restate the immense benefits possible. Morally, they can tell us that the chimpanzee’s mind does not count when considering the opportunities for scientific advancement.
Methodologically, the justification for the Weissman mouse may be extended to the chimp experiment on the basis of utility. Footnote 48 This can be logically explained thus
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1) An “experiment” is prohibited for purpose X on H(human) because of the status of that being, Y;
(Y = ‘H(human) has moral status); Footnote 49
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2) The benefits of purpose X (research on the “human” brain) are positively quantifiable; Footnote 50 so that:
2a. Experiment for purpose X is permitted on M, because it lacks Y; however, such an experiment cannot achieve purpose X because M lacks “necessary neurology”;
(Where M = unmodified mouse)
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3) Purpose X is possible in MChimera.
(MChimera = chimeric “human-like brain” mouse, therefore the second clause in 2a. is reversed)
Because:
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4) M → MChimera is implausible Footnote 51 as a cause of a “human-like” mental state (at point M and in the future, as MChimera ≠ Y);
(→ = transformed)
And consistency means that:
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5) Chimpanzee (C), lacking Y, justifies conducting the experiment X (C → CChimera).
However, because of moral consistency:
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6) If MChimera cannot “plausibly” have Y, then that speaks to two possibilities that justify the experiment in an animal (M or C):
Where human (Y) is the only morally relevant factor, either:
6a. No biological/biochemical/neuronal structure situated/normalized in a nonhuman can be “humanised”; or
6b. No emergent capacities “like Y” in a chimera can possibly be “human.”
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7) Instead, if 6 is false, then: Footnote 52
7a. MChimera/CChimera gains “something like” Y, which would suggest that it is no longer M/C; and therefore:
7b. Creating a chimera with the purpose of being “like H(human)” plausibly results in Y.
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8) If 7b. is at least plausible, then creating MChimera/CChimera is ethically qualified by research norms in the same way that they are conditional in humans. Footnote 53
The approach of Greely and the Report is to proceed with “the principle of benefits,” so that without utility, point 2 would be inoperable; making that case is subject to empirical and qualitative interpretation anyway. However, that is not the only way to read their argument; and I believe an alternative explanation reveals a greater flaw than already present in their unconvincing utilitarian reasoning.
Responding to 6a: Is There Anyone in There?
Greely indicates that there is a fundamental difference between human and nonhuman moral status. Footnote 54 He writes that what “we should care about, morally, is an organism’s mental capabilities,” but “not all mental capacities but the kind of consciousness… that we consider typical of humans.” Footnote 55 Because no other animal has “human consciousness or human-like mental characteristics,” then invasive animal research is ethical, and by suggesting that such capabilities are fixed, the Weissman mouse experiment is ethical as well. Although he anticipates “electronic chimeras” with some sort of unspecified moral status, Footnote 56 no nonhuman animal matters in this sense because of the implausibility of non-human agency. Leon Kass, likewise, finds humanness unique to our own species-specified natures: “Cockroaches and humans are equally bestowed but differently natured”; “humans,” he claims, are the most gifted of Nature’s creatures, Footnote 57 and according to this reckoning, the subjectiveness of being human—a categorical life that only humans experience—is unique. Humans can be “dehumanized” by derogatory or other offensive treatment by others, but not by the absence, reduction, or loss of cells, tissues, or organs. This fundamental basis for human perfectionism, Kass believes, separates our species from all others. Moreover, biology (beyond genetic essentialism) as of itself does not contain moral worth; therefore, creating biological “humanness” in a nonhuman system brings with it no moral advantage either. Such categorical reverence for human life has been elsewhere called into question on the basis of chauvinism Footnote 58 and speciesism, Footnote 59 and, therefore, for my satisfaction, Greely’s claims demand a higher threshold to be true. To do so, he employs the criteria of “mental states” and at their apex is human consciousness.
Given that we are finding more elements of higher capacities in many animals, can this level of human preeminence be maintained? Footnote 60 Research suggests that “human intelligence is best likened to an upgrade of the cognitive capacities of nonhuman primates rather than an exceptionally advanced form of cognition.” Footnote 61 Moreover, the evolutionary tree does not isolate species, and, because of that, contemporary neuroscience research admits that many animals Footnote 62 have rudimentary, incremental, or advanced consciousness. Footnote 63 The components necessary for higher mental abilities are primarily structural, organizational, and morphological, and these vary across species, but are not unique to our own Footnote 64 (there does, however, seem to be something of a higher predetermination about the qualitative/quantitative differences so far detected inimitably in humans). Footnote 65 The human’s unique mental abilities (which vary across living human beings as well) become more in doubt with different species themselves showing varied, and sometimes remarkable, mental states and capacities that mirror those in humans. Footnote 66 To wit, Andrew Fenton claims that there are at least no sufficient philosophical grounds for citing relevant differences between the “interests of chimpanzees and the interests of many of those found in the human population enjoying human-level moral status.” Footnote 67 There is a simple point to all this: the mouse is the easy case; however, these assumptions of unique human metal states should logically be cast aside when considering higher primates. Yet, for all this, in respect to the proposed experiment, the murine or primate chimera will be an entirely unexamined biological and moral entity. How can we make sense of a de novo mental state created in the Weissmann experiment?
In transplant medicine, “humanization” explains the possibilities of xerographs exactly because animals normally lack human immune-incompatible organs. The organs suitable for transplantation are humanized only to the degree that they exist in an animal and would likely survive if transplanted into a human. However, if a functional “human” heart can be situated in an animal, then that at least makes it plausible that a functional brain could be likewise; there is no biological reason (and certainly no philosophical one) that any organ, given the right conditions, could not thrive in an alien system. Prospectively, the practicalities of growing human organs—even those as complex as a brain and forming connections to the body—are possible because of Weissman’s methodology. However, it is suggested that a mouse brain and nothing but will always grow in a mouse, and that a human brain will always and only grow in a human, yet this is not taken to be the case with other organs. If one takes away the biological assumptions made in the murine case—which is the reason that I instigated the chimp model—then what is standing in the metaphysical way of “human consciousness”? No organ ceases to exist (or becomes indefinable) when in another (foreign) body; and its functions, one might suppose, remain intact (a humanized heart in a pig is a “human” heart). Footnote 68 This really does raise some intriguing questions, such as what would we make of a human whose brain is replaced by murine or primate cells in toto? Footnote 69 Would that being be a “mouse,” or a “primate,” or, given the benefit of doubt, still be “human”?
I am content to think that current evidence suggests that a normal mouse—and perhaps even a chimpanzee—lacks advanced indices of human consciousness. Whether animals matter morally (and which ones) is other question altogether. But I think it is idle conjecture to be certain that neuron “humanized” animals are equally without morally relevant capacities, and even more so given the plausibility of de novo capacities brought on by significant transplantations. Human-origin neurons are unlikely to be “sentient” themselves, but given the genetic, biological, and chemical processes that arrange the structures involved with human cognition, human consciousness might be more likely to be present in an in toto transplant. Contrary to the high level of evidence expected in cited experiments to dismiss humanization, others are already showing how partial changes, for example, transplanted human cells introduced into a mouse brain, create enhanced capacities for plasticity and learning that are not present in normal murine behavior, Footnote 70 and that evidence is difficult to dismiss as immaterial or merely cognitive phantoms. Footnote 71 The idea of “humanization” as used in the Report seems categorically problematic because it uses the Weissman mouse’s mindlessness to sustain the irrevocable root of all human worth.
Responding to 6b: How to Tell What a Chimera Will Be Like?
What might anomalies in perception, complex thought, cognition, and consciousness look like in a suddenly mindful chimeric being? If it is plausible that “higher” consciousness can be created in a system de novo, then that being may not be “human,” but it then might have its own “interests” that “it” knows. That would make its life morally significant in the same way that concrete realizations (self-awareness) occur in any other moral agent: it would have rights.
But although we might be able to imagine and even detect bestowed “humanity” in a chimpanzee, it would be more difficult to find that out in an emergent chimeric mouse. In this respect, it is more plausible to find agency in another that we can easily anthropomorphize. Footnote 72 Time and again it has proven impossible to know with certainty that an “other” has the kind of consciousness that makes it matter morally (the problem of “other minds”). This is the baggage of reasoning by analogy. Footnote 73 We often look for evidence and find it most persuasive in animals like us, such as chimpanzees (and other great apes) where arguments of “sameness” are convincing (or at least they are evolutionarily, biologically, and behaviorally plausible). Biology, in some other cases, makes such analogies perplexing; Footnote 74 none more so than in the imaginary machine-computer personhood of HAL9000 or Data; however, we should not idolize such fantastical minds just in the works of fiction. In this respect, much has been written about possibilities and uncertainties, but relatively little has been written about the methods for ascertaining the character of a chimera’s mind, although some have attempted to show that extrapolation would be more or less necessary in respect to the origin of the material and the target (and location) into which it is introduced; the quantity of material transposed; the timing of the transposition; and the type of cell transposed. Often, analogies are evidentially weak because we are ill equipped to detect relevant behaviors in animal subjects; again, the problem of other minds requires ingenious experiments that address methodical challenges and allow for interpretation of observations. When we look for abilities to communicate and socialize, Footnote 75 to have and transmit cultures, Footnote 76 to develop technologies, Footnote 77 and to hold virtues, Footnote 78 we might be less content to see things as “us and them.” However, there remain concerns that consciousness (despite these observations) could be detected or even known by the human inquisitor.
Analogy, therefore, is problematic: If “Y” defines our morality (which is the bedrock on which we treat our own and other species morally), then we ought to be satisfied that it is not present in another being before treating that being as morally inferior. Practically speaking, it is ethically better to err with caution so that a being that might have Y is treated as having Y, rather than to act only with certainty in respect to Y. Footnote 79 The implications if one is wrong are far worse for a being wrongly judged to lack agency, than for wrongly judging an entity to have it (as long as no other ostensible agent is harmed in making or as a consequence of that judgement); therefore, morally, we should take a precautionary turn. That is relatively easy to do regarding other humans; for example, we are comfortable making such assumptions every day about the “person on the omnibus” (and use legal tests for beings at the margins of competency), but such judgments become problematic as we move further away from our own species.
Greely’s group offers up their version of the worst case: humanization trapped in a mouse would “truly be cruel treatment.” Footnote 80 But the possibility of emergent consciousness reverses the usual repugnance imagined by Franz Kafka. In The Metamorphosis, it is too fantastical and abhorrent to even comprehend a person’s dehumanization. However, to the emergent moral status of the actual chimeric being, it is no more trapped than we are in our bodies (a process that is surely of a similar kind to our own realization that we are conscious). Ontologically, we do not need to observe or affirm that the chimera benefits from its existence to make a moral case for its interests (that is done merely by it being an agent); or whether it perceives favorably, or otherwise, its new perception of the world, and that that morally matters. It will suffer as an object of experimentation, of exceptionality, of vulnerability; and it will know that we are the cause of its suffering as it comprehends its pitiful existence confined to a laboratory and experimentation (and eventual autopsy). Whether this being is endowed with a conscious preference to live or an idea of self-determination of the kind we realize ourselves, is unknown to us. (And to define and put into practice what we think would be a worthy life for that being would violate its autonomy.) If higher consciousness did emerge—and we knew about it—then there would be significant moral questions to be asked: not least that it is equally possible that, like any rational being, it will resent a confined existence that is absent of basic rights; and these are the same rights that normally preclude nonconsensual experimentation in human beings.
Conclusion
Sherry Loveless and James Giordano write: “a deepening understanding of the ways that nervous systems and brains are involved in (or invoke) those characteristics that are valued in individuals, groups, and a species should compel and sustain the ways that the organisms that possess such characteristics are regarded and treated.” Footnote 81 For many, there is little to be gained by arguing that a mouse is conscious because its mental states are of a lesser kind to that found in humans. However, if my argument has been successful, then it shows that, for opportunistic reasons, there is more reason to preclude Weissman’s proposed original experiment, and far more to gain from chimpanzee and human experiments. Unless one can find side constraints for doing so—that higher primates matter morally—then not conducting the experiment appears to be illustrative of the squeamishness that utilitarians are known for. Footnote 82 The side constraint, of course, is the moral status of animals themselves.
In this article, I have not attempted to challenge the status of animals in research in general, but rather to question the motivations for involving them in certain experiments. The conclusion I have reached is that the proposed mouse experiment is a fallacious model for studying human neurology. The more representative model—if indeed the scientific case can be made to conduct such animal experiments in the first place—would be the logical step to inserting human neuronal stem cells into a primate. However, if this experiment is illustrative of plausible “humanization” (to the extent that a chimeric primate might have human-like capacities that make it a moral agent), then to the extent that it is plausible, it must fulfill criteria for ethical human research. If there were any categorical doubt still attributed to the fidelity of the chimp chimera’s new brain, then it would be logical to conduct such experiments in human beings. Of course, such experiments are already being conducted, Footnote 83 and there are a growing number of effective ways as well as the scope to examine the human brain unobtrusively and opportunistically. Footnote 84 These experiments are likely to reward us with a better data set because they are realistic to the human condition, rather than those conducted in analogues. Therefore, instead of focusing on chimera policy, one might consider revising the ethical and legal conditions that make research on humans possible. This proposition is not meant to reverse years of human protections in research, but instead questions the grounds for experimentally accessing the real brain diseases and conditions from which humans suffer. Footnote 85 Human research is permitted depending on the conditions of voluntariness, best interest, and proxy-consent. Footnote 86 These conditions might be reconsidered but for the ordeal of revising complex legislation and challenging ethical tradition. Moreover, admitting human patient research explicitly as an alternative to animal research would be a controversial sea change in policy. Footnote 87
Therefore, it begs the question why the Weissmann experiment would be justified at all. Utility would not seem to support such studies if there is a better alternative, or a high cost to a sentient, potentially cognitive, nonhuman being (they face confinement, pain, and ultimately death). Footnote 88 If that is correct, then one would better engage with human participants in research; that does not need faulty utility logic, but is informed by a precautionary understanding of species-neutral agency. The challenge, however, is that the debates about the Weissman mouse—a being that “could not possibly” become a person—are also about the norms of scientific enquiry. First, such an experiment would allow for research that is unconscionable in a human being. It is my conjecture that the Wiessman experiment could be used to avoid clinical ethics, which is why I extended the experiment to a chimpanzee. In so doing, I asked at what point would it become “too human” so that invasive research became inconceivable without consent or its best interests in mind. However, there are also the benefits projected as societal interests: often, as in this experiment, the opportunities and costs are unknown; at the same time, human patients are already suffering from incurable diseases, and with strict conditions on human research, there is an urgency to dissect an analogous state for answers. This is only possible if the fact of moral status can be proven, and, in this way, animals are excluded from the moral community because this befits our experimental curiosity and creates clinical utility. Footnote 89 This logic serves a particular purpose: human vulnerability and dependence drives our scientific ambitions (how we succumb to old age and illness), and establishes the perceived empirical considerations for practical concern. Footnote 90 For some, the sense of urgency to solve actual human cases grounds the humanitarian issue behind much of what neurologists want to know, or what motivates them to dissect the mechanisms that make such behavior possible. There is a clear tension in the kinds of research that scientists want to conduct and the opportunities restricted by ethics and regulation; this can be explained by the values and principles of science, or a moral obligation to save members of our own species while concurrently respecting (and venerating) all human beings as participants in research. Therefore, there is a confounded assumption that the differences between “us” and “them” still make up the most important determinant in the ethics of animal and clinical research; but all the while we are seeking out similarities and engineering comparable models.
The experiments proposed here require observance of (or perhaps ambivalence to) a dubious premise: that the experiments are ostensibly justified because the chimera is “sufficiently like us” to necessitate the research, yet not “sufficiently like us” to preclude research that would otherwise be unconscionable. However, can an argument of comparative fidelity actually go both ways? Or, to put it another way, neuroscience should challenge our intuitions or traditions that rely on nonhuman animals in research. The kinds of experiments that require deep insights into the human being should really start and end with the mind we know.
