The first embryos created from apes – a small step towards a huge ethical problem

Scientists have created the world’s first monkey embryos containing human cells in an attempt to investigate how the two cell types develop side by side. Embryos, which are derived from macaques and then injected into the laboratory by human stem cells, are allowed to grow for 20 days before being destroyed.

For this type of life form we have a term: a chimera, named after a monster of Greek mythology that breathes fire, and was partly a lion, partly a goat, and partly a snake. We hope that part of the human chimera – basically animal bodies with some human organs or other characteristics – could one day offer clues that will help us treat human diseases as well as provide organs for transplantation to humans. But for these purposes, chimeras with a part of man will first have to be born, and this research takes us a step closer to that possibility.

This is ethically controversial, because these creatures could have an ambiguous moral status: somewhere between the human, over which we are not inclined to experiment, and the animal, which we have. The way we will eventually treat chimeras with a part of man will depend on the moral status we assign to them – a task that these latest embryonic experiments only make even more important.

In Greek mythology, it was said that the Chimera was partly a lion, partly a goat, and partly a serpent.
AlexMastro / Shutterstock

Why make chimeras?

There are several reasons for conducting this line of research. For example, chimeras could be created from humans and monkeys to study parts of the brain, so that we could better understand Alzheimer’s disease. Another goal is to grow human organs for transplantation by “deleting” the relevant organ from the animal’s genetic instructions and replacing it with human stem cells to fill a developmental niche.



Read more: Hybrids between humans and animals are coming and could be used to grow organs for transplantation – Libra philosopher


Earlier, the same researchers investigated this avenue in pigs – which is considered ideal because their organs are approximately the same size as ours. However, not enough human cells were needed to create a functional chimera, and research failed.

Monkeys are evolutionarily closer to us, so there is a greater chance that cells will communicate effectively with each other. The stated goal of experiments on humans and monkeys is to understand and perfect the development of chimeras in primates before transferring the technology to pigs.

As we intensively raise and eat pigs, it is considered that there are fewer ethical problems with taking organs from pigs. Therefore, primate research is a springboard, not an end in itself.

Future chimeras

Whether it is a pig or a primate, living chimeras containing human cells are certainly possible in the future. How such animals will look and function will depend in part on the number of non-human and human cells. For example, previous experiments created an individual goat-sheep that had both woolly and coarse hair.



Read more: How do scientists approach becoming part human, part animal, what are the concerns?


This research obviously has a “yuk factor,” meaning it is likely to provoke moral repulsion. If pigs or monkeys eventually develop with humanized traits, this could cause great public inadequacy, which might significantly backward public acceptance of science.

However, this must be balanced with a major shortage of organ transplants. For example, in the U.S., more than 100,000 people are currently waiting for an organ.

A small, partially developed embryo
Researchers had previously created a four-year-old pig embryo that contained human cells.
Cuttlefish USA / Alamy

We tend to get over the yuk factor when it comes to lives. For example, in the production of AstraZeneca vaccines, cell lines derived from fetal cells are used. But behind the yuk chimera factor lies a thorny ethical problem: the question of the moral status of monkeys or pigs that could have a brain closer to human.

Moral status

Moral status is a concept of treating life forms according to their interests and possibilities. For example, it is generally believed that humans have a higher moral status than monkeys, which have a higher moral status than pigs, which have a higher moral status than worms. Moral status is associated with mental abilities such as consciousness, self-awareness, moral capacities, and rationality.



Read more: When does a fetus have a moral status?


In the future, some human-inhumane chimeras could develop mental abilities between ordinary animals and humans. This presents a huge challenge for us who are working to determine the moral status of living beings and the rights and obligations that follow that status.

Moral status is already one of the most controversial areas of practical ethics. Recent work on the topic of “species” provides a compelling case that we have wrongly assigned lower moral status to animals. Nevertheless, human-inhuman chimeras are likely to be considered “smaller” than humans, although it is difficult to determine.

There are two ways to address ethical concerns about the moral status of part-time chimeras. Scientists could genetically arrange human stem cells so that they do not become brain cells – but this may not be possible or even desirable, in the case of building a model for human brain disease.

Alternatively, scientists could allow the birth of such chimeras so that we could study their moral status. This would raise other ethical issues, as it would be necessary for the newborn to be subjected to new tests of cognitive behavior, communication, and other mental abilities.

Hybrid futures

Further into the future, chimera discoveries could provide humans with capacities found elsewhere in the animal kingdom, such as bat sonar. If we accept a moral status based on the abilities of a creature, such improved people may one day be considered superior to us.

Since we are already struggling with issues of equality among people, we seem to be poorly prepared for the ethical challenges posed by future advances in chimera research.

The question of moral status is a philosophical and ethical question. Science could help us discover it – for example, with information about the range of possibilities of non-human animals – but it cannot tell us what it is about. This new research shows that this is a concept that needs urgent attention.

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