This article is the lead piece in a special report that presents the results of a bioethical investigation into chimeric research, which involves the insertion of human cells into nonhuman animals and nonhuman animal embryos, including into their brains. Rapid scientific developments in this field may advance knowledge and could lead to new therapies for humans. They also reveal the conceptual, ethical, and procedural limitations of existing ethics guidance for human‐nonhuman chimeric research. Led by bioethics researchers working closely with an (...) interdisciplinary work group, the investigation focused on generating conceptual clarity and identifying improvements to governance approaches, with the goal of helping scholars, funders, scientists, institutional leaders, and oversight bodies (embryonic stem cell research oversight [ESCRO] committees and institutional animal care and use committees [IACUCs]) deliver principled and trustworthy oversight of this area of science. The article, which focuses on human‐nonhuman animal chimeric research that is stem cell based, identifies key ethical issues in and offers ten recommendations regarding the ethics and oversight of this research. Turning from bioethics’ previous focus on human‐centered questions about the ethics of “humanization” and this research's potential impact on concepts like human dignity, this article emphasizes the importance of nonhuman animal welfare concerns in chimeric research and argues for less‐siloed governance and oversight and more‐comprehensive public communication. (shrink)

To provide a theoretical basis for the common view that moral status comes in degrees, many philosophers endorse ‘two-factor’ accounts of the foundations of moral status. These accounts postulate one or more properties which endow individuals with moral status, and one or more other properties which increase the moral status of those who possess them. Critical assessment of two-factor accounts has focused on their implications, especially for humans who lack the properties thought to increase individuals’ moral status. Unfortunately, this approach (...) has led to an impasse. To try to break it, the present manuscript instead assesses the assumption on which two-factor accounts are based, namely, possession of one or more properties, what I call ‘moral status enhancing’ properties, increases their possessors’ moral status. I argue that two challenges, the problem of relevance and the need for a threshold, reveal that there are no moral status enhancing properties, hence, no degrees of moral status among those who matter morally. (shrink)

The moral status of human-animal chimeras that have human brain cells is especially concerning. The concern is that such animals have the same high moral status as human beings. Why? Julian Koplin suggests that support for this concern is based on this claim: capacities unique to humans gives one a high or full moral status. Koplin then proceeds to convincingly object this claim. However, I argue that the concern is instead based on a different claim: for those humans who do (...) have a high moral status, it is their (or some of their) mental capacities that confer this high moral status. Since having a human brain that is not too impaired is sufficient for having these mental capacities, and human-animal chimeras -- with brains composed of a sufficient number, type, and structure of human cells -- will have a human brain that is not too impaired, it follows that such animals would have the same moral status as human beings. (shrink)

Blumenthal-Barby (2024) argues that bioethicists should stop using the concept of "personhood" in both well-established bioethics debates (e.g., regarding cognitive disability) and emerging ones (e...

In “Human‐Animal Chimeras: The Moral Insignificance of Uniquely Human Capacities,” Julian Koplin argues against the views that all uniquely human traits have moral significance or that all the traits humans have in common with other animals “are morally insignificant.” He recommends instead the adoption of “a better framework for thinking about the moral status of part‐human beings,” one that emphasizes the “phenomenal value (or disvalue)” chimeric animals are likely “to enjoy (or suffer).” If the moral status of these chimeric animals (...) is grounded in the phenomenal value of their interests—that is, their interests as nonhuman animals—current protections for animals used in research may be inadequate to protect those interests. (shrink)

The use of nonhuman animals in research has long been a source of bioethical and scientific debate. We consider the oversight and use of nonhuman animals in chimeric research. We conducted interviews with twelve members of embryonic stem cell research oversight committees, nine members of institutional animal care and use committees, and fourteen scientists involved in human–nonhuman‐animal chimeric research in different areas of the United States. Interviews addressed animal welfare and conceptual issues associated with moral status and humanization of nonhuman (...) animals that contain human cells. Our findings suggest that concepts of enhanced moral status and consciousness are not very useful in human–nonhuman‐animal chimeric research in part because their meanings are not easily defined, which presents challenges to applying the concepts in research. Instead, scientists and oversight committee members we interviewed seemed to rely on standard assessments of changes in animal welfare when focusing on the ethics of human‐animal chimeric research. (shrink)

Greely’s target article outlines six categories of ethical issues associated with human brain surrogate research. Some of these issues are familiar from other research contexts; others, less...

With its provocative title, Blumenthal-Barby’s (2024) Target Article is an important addition to the critical work on using ‘personhood’ in bioethics. I suggest it bears on any philosophical discus...

The burgeoning field of biomedical research involving the mixture of human and animal materials has attracted significant ethical controversy. Due to the many dimensions of potential ethical conflict involved in this type of research, and the wide variety of research projects under discussion, it is difficult to obtain an overview of the ethical debate. This paper attempts to remedy this by providing a systematic review of ethical reasons in academic publications on human-animal chimera research. We conducted a systematic review of (...) the ethical literature concerning human-animal chimeras based on the research question: “What ethical reasons have been given for or against conducting human-animal chimera research, and how have these reasons been treated in the ongoing debate?” Our search extends until the end of the year 2017, including MEDLINE, Embase, PhilPapers and EthxWeb databases, restricted to peer-reviewed journal publications in English. Papers containing ethical reasons were analyzed, and the reasons were coded according to whether they were endorsed, mentioned or rejected. Four hundred and thirty-one articles were retrieved by our search, and 88 were ultimately included and analyzed. Within these articles, we found 464 passages containing reasons for and against conducting human-animal chimera research. We classified these reasons into five categories and, within these, identified 12 broad and 31 narrow reason types.15% of the retrieved passages contained reasons in favor of conducting chimera research, while 85% of the passages contained reasons against it. The reasons against conducting chimera research fell into four further categories: reasons concerning the creation of a chimera, its treatment, reasons referring to metaphysical or social issues resulting from its existence and to potential downstream effects of chimera research. A significant proportion of identified passages fell under Category C. We hope that our results, in revealing the conceptual and argumentative structure of the debate and highlighting some its most notable tendencies and prominent positions, will facilitate continued discussion and provide a basis for the development of relevant policy and legislation. (shrink)

In “Human‐Animal Chimeras: The Moral Insignificance of Uniquely Human Capacities,” Julian Koplin explores a promising way of thinking about moral status. Without attempting to develop a model in any detail, Koplin picks up Joshua Shepherd's interesting proposal that we think about moral status in terms of the value of different kinds of conscious experience. For example, a being with the most basic sort of consciousness and sentience would have interests that matter morally, while a being whose consciousness featured the riches (...) of loving affection, say, might have greater moral status and therefore deserve some sort of priority if the interests of the two beings conflicted. This approach represents an improvement over the more common, transparently anthropocentric habits of thinking about moral status, whether in connection with evaluating human‐animal chimera research, deciding what one can ethically eat, or pursuing some other moral inquiry. (shrink)

In this conversation, three researchers from the fields of developmental biology and stem cell science—Ali Brivanlou, Lorenz Studer, and May Schwarz—speak about the importance of conducting chimeric animal experiments. The scientists describe some of the stem cell-based chimeric research being conducted in the United States, responsibilities they have in using modified animals for experiments, and things they would like the public to understand about this research. This conversation illuminates not only what chimeric animal researchers are doing in the lab but (...) also how their work may benefit society and where this science might go in the future. (shrink)

Non-human animal chimeras, containing human neurological cells, have been created in the laboratory. Despite a great deal of debate, the status of such beings has not been resolved. Under normal definitions, such a being could either be unconventionally human or abnormally animal. Practical investigations in animal sentience, artificial intelligence, and now chimera research, suggest that such beings may be assumed to have no legal rights, so philosophy could provide a different answer. In this vein, therefore, we can ask: What would (...) a chimera, if it could think, think about? Thinking is used to capture the phenomena of a novel, chimeric being perceiving its terrible predicament as no more than a laboratory experiment. The creation of a thinking chimera therefore forces us to reconsider our assumptions about what makes human beings (potentially) unique (and other sentient animals different), because, as such, a chimera’s existence bridges our social and legal expectations about definitions of human and animal. Society has often evolved new social norms based on different kinds of (ir)rational contrivances; the imperative of non-contradiction, which is defended here, therefore requires a specific philosophical response to the rights of a thinking chimeric being. (shrink)

Given the broad coverage of “Human Brain Surrogates Research: The Onrushing Ethical Dilemma,” this commentary focuses on the section “human/nonhuman brain chimeras,” and specifically, the questions...