August 13, 2006
Should Human Animal Chimeras Be Banned?

The Scottish Council on Human Bioethics has released a report entitled Embryonic, Fetal and Post-natal Animal-Human Mixtures: An Ethical Discussion where they discuss what scientists are doing with mixing human and animal cells and the ethical issues arising from this work.

Genetic Human-Mouse Chimeric Fetuses

Recently Scientists at Stanford University injected human neuronal stem cells into mouse fetuses, creating mice whose brains were about 1% human. By dissecting the mice at various stages, the researchers were able to see how the added brain cells moved about as they multiplied and made connections with mouse cells [91]. The same scientists now want to add human brain stem cells that have the defects that cause Parkinson's disease, Lou Gehrig's disease and other brain ailments and study how those cells make connections. Indeed, scientists suspect that these diseases, though they manifest themselves in adulthood, begin when something goes wrong in early development.

Because of this, the Stanford team is also thinking about making chimeric mice whose brains are 100% human. However, they suggest that if the brains look as if it is taking on a distinctly human architecture - a development that could suggest a specific amount of 'humanness' - they could be killed. On the other hand, if they look as if they are organising themselves in a mouse brain architecture, they could be used for research [92,93].

In January 2005, an informal ethics committee at Stanford University endorsed the proposal to create mice with brains made nearly completely of human brain cells. The chairperson of this committee indicated, in this respect, that the board was satisfied that the size and shape of the mouse brain would prevent the human cells from creating any traits of humanity. But just in case, the committee recommended closely monitoring the mice's behaviour and immediately killing any that display human-like behaviour [94].

They go on to briefly describe experiments that have been done with chimeric fetuses of human cells with sheep, monkey, and pig cells. In each case human stem cells were injected into locations in animal fetuses. They also discuss the potential to introduce human stem cells at a much earlier stage in development where the injected cells can be expected to become a larger percentage of the resulting animal's total cell count.

In 2003, Scientist at the South Korean firm Maria Biotech, were reported to have injected human embryonic stem cells labelled with a fluorescent protein into 11 mouse blastocysts which later developed. The embryos were then carried by foster mice, whereby five offspring were born with fluorescence in tissues including the heart, bones, kidney, and liver. However, the scientists terminated the project after having to address "severe protests" from the public [101].

They take a hard line against any tinkering that results in a creature that has human neurons sharing a brain with animal neurons.

  • The incorporation of human stem cells into post-blastocyst stages of non-human embryos should only take place if it can be demonstrated that they cannot contribute to the germline or brain cells of the animal.
  • The incorporation of non-human stem cells into post-blastocyst stages of human embryos should only take place if it can be demonstrated that they cannot contribute to the germline or brain cells of the human being.
  • The incorporation of human pluripotent or totipotent stem cells into a non-human blastocyst or its preliminary embryonic stages should be prohibited.
  • The incorporation of non-human pluripotent or totipotent stem cells into a human blastocyst or its preliminary embryonic stages should be prohibited.

This is an interesting position. They draw the line against mixing human neurons with non-human neurons. Perhaps they see human neurons as somehow sacred.

Okay, what is the appeal of this position? First off, it avoids the really difficult problem of defining what is a rights-possessing entity. Make sure nothing that is a mix of human and non-human mind comes into existence. Then we never have to face that question. Well, that's the hope anyway. But the hope is wrong. We will end up having to face that question anyway when someone tinkers with another species and just changes its DNA to make it smarter without using human DNA to create the smarter result. We will face the question when people start creating human offspring that have modifications of genes that govern cognitive ability. We will face that question when artificial intelligences are created.

The need to create a scientific definition of humans will be forced upon us by technological advances. That definition (or, rather, definitions since consensus will not be possible) will threaten religious definitions, ideological definitions, and other definitions based upon fantasies of what we wish to believe is nature.

But before we start modifying human nature or creating other intelligent lifeforms we already increasingly face another threat to how we view ourselves: Genetic and neurobiological advances will gradually undermine many beliefs about the nature of humans. Worse, the challenge of what should be considered human will (I predict) be challenged when looking just at genetic variations which exist in humans.

For example, more genetic variations that contribute to violence and criminality will be found. Probably some genetic variations will be found that contribute to psychopathy. Should we consider amoral totally unempathetic minds as humans? We'd be unwise to grant rights to an artificial intelligence with those qualities. Should our standard for rights possession be lower for humans than for AIs or animals uplifted by genetic engineering that raises their intelligence?

Delaying the day we have to face the question of whether chimeras possess human rights or human souls might make sense even if creation of chimeras is eventually allowed some day. The longer we delay the better will be our scientific understanding of human nature and of the cognitive qualities needed to maintain a rights-based society.

A second reason for keeping humans unmixed with other species is that doing so preserves the ability of many humans to feel that humans are special and apart from the rest of life. Many people see humans as special due to having souls which other species do not have. But if a human-chimp chimera could be created the question arises: Would it have a soul? Suppose that a creature looked perfectly human but somehow had 10% of its brain cells from another species. Would it have a soul? It'd have more human brain cells than, say, an Alzheimer's patient. So would it have a soul?

A third reason to oppose creation of human-animal chimeras is to avoid suffering in the resulting creatures. But suppose scientists include a small enough percentage of human cells that the resulting animal thinks and acts like an animal of its type. Or suppose the human cells were genetically modified to be more compatible with, say, neurons in a mouse's brain and that the mouse brain was kept as small as a normal mouse's brain. Potentially that'd avoid the problem of creatures which are not shaped in a way that causes them suffering. Also, the mouse would not possess any higher level of awareness than a normal mouse has.

It seems to me that the biggest benefit of totally banning the creation of human-animal chimeras is that it avoids our feeling confused about how we should treat the results. But we are going to have to wrestle with all the ethical questions that chimeric creatures present us with whether or not we create chimeric creatures. Also, even if the creation of such creatures is banned inevitably people will create them illegally. So we'll still have to decide at some point what criteria to use when weighing what rights to grant them or whether to destroy them upon discovery.

Before taking the line that we should just ban anything that seems yucky or weird consider the potential benefits from letting scientists create chimeras. For example, scientists can study human diseases by putting human cells with human genetic disease into animals. Also, use of animals to grow organs for transplant might work if the organs were grown from the fetal stage using human stem cells injected into the fetus.

Share |      Randall Parker, 2006 August 13 11:00 PM  Bioethics Humanity Definition

Antinomy said at August 14, 2006 4:32 AM:

>"But just in case, the committee recommended closely monitoring the mice's behaviour and immediately killing any that display human-like behaviour"

If the animal starts displaying human behavior, it seems like that would be an argument that summarily killing it is immoral.

Kurt said at August 14, 2006 9:04 AM:

The first task is to define what exactly is ment by the term "soul". I have yet to hear or read an objective definition of this word. I have always assumed that "soul" ment human consciousness or identity (i.e. your memories and what not) that define how you are. However, some religious people have told me that this is not the case. However, they still failed to define what "soul" ment to me.

It seems that terms and nomenclature need to be defined first.

Doug said at August 14, 2006 10:14 AM:

In the endnotes to the Second Discourse (and writing before Darwin, of course), Rousseau wondered aloud as to whether humans and apes were different races of the same species. He saw that a breeding experiment would largely settle the question, but he said, "How can such an experiment be undertaken in civil society?" (I'm quoting the English translation from memory, as best I can.) He left it to one who considers well to think of undertaking the experiment outside of civil society.

jim moore said at August 14, 2006 7:10 PM:

Why not use chimp cells instead of human cells. The results should be fairly similar, not exact but good for preliminary research.

Garson Poole said at August 15, 2006 12:36 AM:

Since this is the FuturePundit blog here is a light-hearted exercise in envisioning the future. When the first Stanford mouse displayed human-like qualities during an intelligence test the scientists decided that all the mice would have to be "sacrificed" according to the protocol approved by the ethics committee. This stunning news was transmitted to the world via the blog of an undercover PETA (People for the Ethical Treatment of Animals) member on the janitorial staff of the lab. Radical animal rights advocates demanded that the researchers and the ethical committee members should be "sacrificed" instead of the mice. An impromptu committee of Hollywood animal lovers offered to provide all the mice with loving homes and lucrative contracts to appear in remakes of the movies "Willard" and "Ben" starring mice instead of rats. Disney offered to care for the animals if the copyright on "Steamboat Willie" the debut film of Mickey Mouse was extended another forty years.

Members of an animal rights splinter group broke into the laboratory to "liberate" the creatures, and the mice thanked them profusely. They recounted their ill treatment in small metal cages, and requested Perrier instead of tap water in their dispensers. Next, they designed exercise wheels with superior ergonomics, and bedding material with excellent fluffiness. The climax of the saga occurred at the International Court of Human Rights which was renamed for the occasion to be the International Court of Mammal Rights. Of course, many rodent-like lawyers have appeared before the court in the past but for the first time a laboratory mouse brandishing a recently acquired Stanford Law degree plead for its own bodily existence before the bench. The lives of the mice were spared.

Meanwhile there was an astonishing development that none of the researchers anticipated. Some of the brain cells merged with other mice cells and redifferentiated into germinal cells that subsequently migrated to the gonads. But that is another story.

Garson Poole said at August 15, 2006 1:12 AM:

On a more serious note, I think that Jim Moore’s suggestion above is superb. Before placing human cells in mouse brains one could place chimp cells in mouse brains. In addition, researchers can identify a collection of cognitive tasks that chimps perform well and that mice perform poorly. Now, an experimental strategy for evaluating the effects of brain cell substitution is possible. The performance of mice with different brain cells can be compared on a suite of cognitive tasks. This can be done before human cells are used as a significant fraction of brain-matter.

In fact, if there is another animal with cognitive skills that differ significantly from mice and that has a lower degree of apparent brain capacity than chimps then I suggest using that other animal first. Once again, the performance of mice with different brain cells can be compared on a suite of cognitive tasks.

Brett Bellmore said at August 15, 2006 4:12 AM:

Why use human instead of chimp cells? Because this isn't a disinterested search for knowlege, we're looking for things that will help humans, and research with chimp cells would not be as directly applicable.

Garson Poole said at August 15, 2006 7:59 AM:

The proposed Stanford experiment will "create mice with brains made nearly completely of human brain cells." The ethics committee recommends "monitoring the mice's behavior and immediately killing any that display human-like behavior."

The potential dangers of this premature and crude approach to scientific advancement are enormous I think. Suppose the mice do show some signs of advanced intelligence and are killed. This will result in a major scandal and the scientists will be denounced as “inhuman monsters” by many animal rights activists. These activists will probably compare the work to the experimental creation of mentally-impaired humans followed by their deliberate destruction. The “severe protests” that occurred in Korea might seem mild in comparison. The entire area of testing human cells in animal chimeras will suffer a tremendous blow.

It is much better I think to attempt to collect persuasive experimental evidence that mice with brains containing human cells will not be capable of human-like cognition. The experiments I suggest above might provide a framework for collecting this evidence by first using non-human brain cells in mice to see if cognition is altered.

Dezakin said at August 15, 2006 9:36 AM:

This whole thread is ludicrous. Its not the cells or the DNA, its the configuration. A clump of human nerve cells configured in a mouse brain is going to have no more or less ethical issues than mouse cells configured in a mouse brain. The most advanced intelligence plausible in a mouse is going to still be significantly lower than your typical housecat.

If we are concerned about the condition of mice, it should be on ethical grounds alone rather than if they artifically are created with some human-like nerves.

Garson Poole said at August 15, 2006 10:57 AM:

The development of brain structures during embryonic development is determined in a fundamental way by the genetic programming within the brain cells and by inter-cellular signaling. If all the brain cells of a developing mouse are actually human cells then those cells will attempt to build a human-type brain via cell signaling and via the internal cellular programming. The internal programming is based on the regulation of protein expression and the regulation of molecules that bind to DNA. Neurons migrate and interconnect based on biochemical signals such as chemical gradients that are created by the brain cells during development.

However, the human cells will be unable to build a human brain. The skull shape of the mouse is a fixed limitation that will interact with the unfolding development programs of the human brain cells. The resulting brain will not be a human brain and it will certainly not be a standard mouse brain. It will be an abnormal distortion and amalgamation. The cognitive properties of this abnormal brain can not be predicted in advance with complete assurance in my opinion. Currently, we do not even know how higher-level cognition is implemented in the brain.

Randall Parker said at August 15, 2006 4:16 PM:

Garson, Jim Moore,

I'm guessing the researchers want to take neurons known to carry various human genetic neuronal defects and grow them in mice to get access to lots of live human neurons that produce brain diseases.


Yes, of course the configuration of the neurons is crucial. Human neurons in a mouse are far too few in number to produce a configuration that will do anything interesting.

I see the reaction that demands keeping human neurons out of mice or rats as the neuronal equivalent of the Monty Python Meaning Of Life scene where the Catholic kids in Yorkshire England walk out of the house singing "Every sperm is sacred". We are to believe that every human neuron is sacred. Maybe each neuron contains part of a human soul? Or a soul attaches to a bunch of neurons?

I'm personally curious to know whether a mouse brain made up of mostly human neurons could even allow the mouse to function like a mouse. Though doing this experiment with neurons from other species would yield lots of interesting insights as well.

Tom said at August 15, 2006 5:40 PM:

Maybe there's an ethical issue here, and maybe there isn't. So who decides? A bunch of scientists using some set of ethics that most people wouldn't sign on to. I think it would make a lot of people squeamish, because we don't know where the line should be drawn. If there is absolute truth as to whether this kind of thing is right or wrong, and some truth as to where the boundaries of humanity lie, we haven't much in the way of guidance. So my guess is that most people would say that it isn't worth the moral gamble, and leave it at that.

Randall Parker said at August 15, 2006 7:45 PM:


There are so many legal jurisdictions in the world that I expect some jurisdictions will allow the creation of assorted chimeras.

Pauloson said at August 15, 2006 9:21 PM:

And what about injecting human neuronal stem cells into, say, horse fetuses. A horse has a much larger skull than a human. Then maybe a bit of tinkering with the developmental layers of that brain, so that it makes a good use of all that space. I would love to see the results!

Tom said at August 16, 2006 4:05 AM:

Randall: China has been accused of harvesting organs from inmates, and strongly pushing abortions for mothers that already have a child. I'm not even going to bring up what the Nazis did. That another society does something that we consider morally questionable is no reason for us to do the same.

Pauloson: "And what about injecting human neuronal stem cells into, say, horse fetuses . . . I would love to see the results!"

Mr. Ed?

Bob Badour said at August 16, 2006 6:57 AM:


Randall's site explores and tries to illuminate what the future holds in store for us. Saying that it will happen is not the same as saying we should do it.

Garson Poole said at August 18, 2006 12:50 AM:

Randall Parker has added another item to his blog that is directly relevant to this topic. So, if anyone cares, I attached my next remark to the comment section of the new blog item here.

I almost spluttered what I was drinking on my keyboard when I read Tom’s witty comment “Mr. Ed?” The television series was created from 1961 to 1966 so I am not sure how many will understand the reference.

Randall Parker said at August 18, 2006 6:16 PM:


I didn't immediately get Tom's reference. But now I remember. "A horse is a horse, of course, of course".

A horse is a horse, of course, of course, And no one can talk to a horse of course That is, of course, unless the horse is the famous Mister Ed.

Go right to the source and ask the horse
He’ll give you the answer that you’ll endorse.
He’s always on a steady course.
Talk to Mister Ed.

People yakkity yak a streak and waste your time of day
But Mr. Ed will never speak unless he has something to say

A horse is a horse, of course, of course,
And this one’ll talk ‘til his voice is hoarse.
You never heard of a talking horse?

Well listen to this: "I'm Mister Ed."

cAm said at December 4, 2006 11:46 AM:

the only reason they are "illegel" is because most of the people in the whitehouse are "christian"...
its legel in europe

Alyssa said at January 7, 2008 3:18 PM:

This is all really interesting, but is there a valid reason behind the whole thing, I mean, what about when you start playing around with human embryos, wouldn't that bother any of you?

Harry Lackey said at June 23, 2009 11:45 AM:

As far as a human chimera possessing rights, I'd say that would have to be considered on a case by case basis. Afterall, we do not give driver's licenses to those who have severe mental handicaps. And we don't give concealed handgun permits to violent criminals. The rights of a human animal chimera should vary according to what the creature is capable of having. But all creatures human should be treated with the same respect as everyone else wants to be treated.
As for my feeling on the issue of the creature having a soul, I would rather treat the creature like it has a soul and find out later it does not have one, than to treat the creature like it has no soul and it really did have a soul. If the creature was intelligent enough to understand the things we can, the latter of the two mistakes would result in a neglected soul going to Hell for eternity some day. And the soul of a human animal chimera would suffer no less in Hell than the soul of one of us fellow 100% humans would.
Which that last thought brings me to this. You the reader, as a fellow 100% human, have you ever given any thought to your own soul? Was there ever a time in your life when you called upon the Lord for forgiveness of your sins, accepted God's only Begotten Son, our Lord Jesus Christ as your saviour and was willing to repent from sin. Your eternity is the most important thing of all, whether you realize it or not.
107 people die around the world each minute. According to Matthew 7: 13 & 14 most of them are going to Hell. How many souls do you think dropped into Hell while you were reading this comment...I plead you not to become one of them.
I'll leave off with this thought...In Revelation 4:6 thru 9, of The New Testament, there is the mention of the Four Beasts who sit around The Throne of God, and praise God saying,"Holy, holy, holy, Lord God Almighty, which was, and is, and is to come". For those who have an intrest in chimeras, the discription of the Four Beasts certiantly sounds like they have the appearance of mosais chimeras, although I doubt they are chimeras. Of course, that should mean nothing to a person who leaves this life never becoming a christian. That person will never see the Throne of God, Heaven or those Four Beasts anyway.

Harry Lackey said at June 23, 2009 12:36 PM:

This is to Kurt fron August 14, 2006 @ 9:04 AM. What you were thinking of as a soul is your spirit. That goes back to God when you leave this life. If you are a born again christian, you will receive a new spirit as well as a new body and a new name in that new world. This old world will some day no longer exist. Your soul is the bare essence of you and nothing else. That is what's you. The way I understand it is, it will be as you are created for the first time in that new world. You'll be different, who you are will be different, your intrests will be different, your personality will be different, the world we will be in will be different. The form of "man" will no longer exist. Scripture teaches that we will be different creatures like unto the angels. It will be a new world where this world and this life never existed. However for those who never became a christian, they will be given a memory of this old world so their past, and what they will then see as their old miserable life, will always haunt them as they suffer in Hell.

Eddie said at November 20, 2009 11:32 PM:

There's no such thing as a soul you christians, if a chimera is created by a scientist, he has the right to do what he pleases with it, as it is his creation and theres no reason to allow christian nonsense to get in the way of science.

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