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Dr Calum MacKellar asks about the prospect of crossing humans with animals, which could be manufactured by modern science

Dr Calum MacKellar

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In 2016, US scientists were told that research may be funded to develop human-nonhuman chimeric embryos.

These are embryos formed from the combination of human and nonhuman embryonic cells. It is believed that these may be useful to investigate human development, disease pathology and organ transplantation.

The word chimera, as such, was defined by Homer, the ancient Greek author, in his mythological account of the Iliad. He indicated that the raging Chimera ‘was of divine stock, not of men, in the fore part a lion, in the hinder a serpent, and in the midst a goat, breathing forth in terrible wise the might of blazing fire’.1 None of this Chimera’s parts were human but the term now defines a category which includes all human-nonhuman interspecies beings.

Legalised in UK

It was, in fact, the UK which became the first country in the world to legalise the creation of such mixed human-nonhuman embryonic entities. In 2005, the House of Commons Science and Technology Committee even indicated that society ‘should not shy away’ from placing human embryos in animals for gestation.2

Furthermore, in drafting the Human Fertilisation and Embryology Act 2008, 308 Members of the House of Commons voted to allow the insemination of animals with human sperm against only 183 who believed this to be completely unethical.3 This made the UK unique in Europe since researchers would be arrested by the police for such experiments in countries such as Germany, France, Switzerland and Norway.

The screaming human-mouse?

But with respect to the research being considered by the UK and US scientists, it is now possible to ask whether the interspecies embryos being created could eventually give rise to chimeric monsters, such as the mythical Minotaur (who had the head of a bull and the body of a man).

This seems unlikely, but if the researchers did mix human and chimpanzee embryonic cells, the possibility of something being born alive (a humanzee) may eventually be a reality, if they tried hard enough.

Actually, one of the ethicists working on this project in the US, David Resnik, was adamant that clear guidelines were necessary, indicating in 2016, with respect to human-mouse research, that: ‘The spectre of an intelligent mouse stuck in a laboratory somewhere screaming ‘I want to get out’ would be very troubling to people.’4

Ethical demarcation lines

Even if the mixed embryos do not develop very far, ethical dilemmas are already present for Christians who believe that human embryos reflect the image of God and should be protected as soon they come into existence. It is very difficult to know whether these chimeric embryos should be recognised as reflecting the image of God, giving them full moral value. Recognising the moral worth of chimeric embryos is only possible if specific factors exist which can be used to determine boundaries between those beings that do, and those that do not, have this value and worth.

The importance of a clear demarcation or boundary between the human and nonhuman was emphasised by American ethics commentator, Leon Kass, who indicated: ‘All of the boundaries that have defined us as human beings, boundaries between a human being and an animal on one side and between a human being and a super human being or a god on the other … These are the questions of the 21st century and nothing could be more important.’5

Until now an unmistakable line has existed between the human and all the other animal species. But the creation of human-nonhuman combinations may completely undermine this boundary. If doubts or uncertainties exist in a significant number of mixed beings, or as soon as the image of God is not acknowledged in certain individuals for whom it should be considered, the whole concept of recognising the image of God begins to be undermined, since it becomes difficult to apply.

Societal order in question

In 2006, Christian bioethicist Nicholas Tonti-Filippini (1956–2014) argued that the creation of human-nonhuman embryos is an offence against a Christian view of bringing persons into existence.

For him, when a scientist mixes human and nonhuman embryonic cells ‘he or she has begun to confuse the identity of what is or is not human and what or who is or is not made in the image and likeness of God, and does or does not count as my neighbour’.6

As a consequence the foundational basis of the whole societal order would be brought into question, since a clear demarcation of full moral value and worth is essential for a civilised society to survive.

The social consequences resulting from the creation of beings of uncertain dignity should, therefore, not be underestimated. The monstrous Chimera, symbolic in ancient mythology of some frightening disorder threatening both society and humanity with chaos, is a very appropriate warning.

All species equal?

Of course, it may be possible to argue that there are no ethical concerns (other than individual biomedical and psychological risks) with the creation of human-nonhuman combinations, if all biological species were freely accorded full and equal rights. However, society and Christians do not do this, and it is difficult to evaluate beforehand the kind of worth and hence the extent to which specific protective rights should be accorded to new human-nonhuman combinations. As a result, the following three options can be considered:

First, if these entities are unfortunately created with dubious moral status, they can be given the benefit of the doubt as to their full moral value and worth reflecting the image of God while allowing them to develop to term. It would indeed be ethically wrong to kill an entity who may be created in the image of God. However, if they then prove to be associated with biomedical developmental disorders, psychological problems or societal inequalities and prejudice, people may eventually decide that they should never have been created in the first place.

Secondly, society can create certain kinds of human-nonhuman combinations and kill them before they develop to any advanced stage because the general public cannot, as yet, deal with the ethical issues which they pose. This was the solution chosen by the UK Parliament in 2008. But in this case, there is also the risk of killing a living entity, out of prejudice, which may reflect the image of God.

Finally, society can decide not to create certain kinds of human-nonhuman combinations because it cannot, as yet, deal with the ethical and societal consequences and instability which they initiate. Indeed, in some cases, it seems that a clear answer concerning the moral nature of some created human-nonhuman entities is virtually impossible to obtain.7 This implies that if the moral status of such combinations cannot be determined without creating them, that in itself should be a sufficient argument against creating such entities.

Urgency for Christians

In conclusion, while recognising the possible usefulness of interspecies research in some circumstances, Christians must begin to examine, urgently, whether possible future human-nonhuman interspecies beings reflect the image of God and whether they have inherent moral worth and value.

Dr Calum MacKellar, is the Director of European Bioethical Research, Edinburgh.


1 Homer, The Iliad, (1924) (trans.) A.T. Murray (London; Loeb classical Library 6/180.

2 House of Commons Science and Technology Committee, Human Reproductive Technologies and the Law: Fifth Report, Session 2004-05, Volume 1, London: Stationery Office, 2005, page 31.

3 Hansard, 22 October 2008, Division 287.

4 Antonio Regalado, Human-Animal Chimeras Are Gestating on U.S. Research Farms, MIT Technology Review, 6 January 2016, https://www.technologyre-view.com/s/545106/human-animal-chimeras-are-gestating-on-us-research-farms/

5 Leon Kass quoted in Smith, W.J., Is the world ready for a superboy? – or a dogboy? Dallas Morning News, 13 November 2005.

6 Tonti-Filippini et al. (2006), Ethics and Human-animal Transgenesis National Catholic Bioethics Quaterly 6(4): pp. 689-704 (p.704)

7 Tonti-Filippini et al. (2006), Ethics and Human-animal Transgenesis National Catholic Bioethics Quaterly 6(4): pp. 689-704 (p.696)